Project: Build an On Board Diagnostics System for a carb'd car

[Buzo]

Based on the succesful diagnostics I recently made in my car, I thought it would be good idea to build an interface that would automatically tell you which sensor is faulty, -similar to the one in the FI cars-.

So the ECU in a Fuel Injection car has a LED that blinks pre-determined number of times when the check engine signal comes on, to tell you there is something wrong in the system.

The project consists in adding a PCB with a PIC microprocessor and monitor the ECU inputs and outputs and make a LED blink if there is a missing input/output/start up secuence.

There are digital and analog inputs to the ECU in a carbureted car

DIGITAL INPUTS
Shift Position
Clutch
Vacuum Switches A and B
Ignition
Start, etc

ANALOG INPUTS
TA and TW sensors
O2 sensor, etc

OUTPUTS
The ECU is a solenoid valve controller, so I believe all the outputs are digital. Either they are at 12V or at 0V at any given time.

Let me start with the idea for the digital ones: Vacuum switches A and B are calibrated to switch at different vacuum levels, so the PIC will monitor the start signal, then Switch A will switch first and Switch B second as the engine "builds up" vacuum. If it doesn't happen in that secuence something is wrong and the LED will Blink "n" times, but will keep monitoring every other start in case the failure fixes itself (yeah).

The Analog inputs can be monitored with comparators to tell the PIC they are changing their value through the time and driving conditions. I.e. The O2 sensor produces a voltage of .4V when lean and .6V when rich, so compare against .5V. The comparator's output should be changing constantly. If it stays ON or OFF even after the car is warm, the LED should blink.

I have all I need right here at home to complete this project, I'll make one for me, but will share all the information with you guys (if interested) as I progress.

Let's wait if it works and then we'll figure out what else can be done with this basic OBD. It would be very helpful for those still with the stock carb I think.

[Dr_Snooz]

:bow:

Very cool stuff.

[lostforawhile]

don't forget the engine senses rpm, and there's an electronic switch built into the cluster that tells the car when it's going over 5 miles an hour, this changes the status of the inputs and outputs, the problem with doing this, is the controller doesn't have sensors for everything, it's a Frankenstein system of vacuum controls and electrical controls that don't actually interface with each other in any way, in other words one system doesn't know what the other is doing, eg. the air jet controller, modifies mixture by vacuum controls depending on barometric pressure, it can be completely screwed up, and the control unit doesn't know. This is why it's so hard to get these systems right, two independently operating systems not in communication with each other but causing interaction between the two, depending on what they are doing. the ECU doesn't have all digital outputs either, the valves that control the mixture don't work on straight DC, it's a square wave, the control box changes the frequency of this square wave to modify the mixture, hence the name frequency control valves, you have other things also going on, such as the EFE heater, it has an independent control circuit and heats the mixture going through it on start up, also the system that controls air intake temp is completely vacuum controlled , it can influence the mixture, there is also an air intake sensor that can switch in a resistor to delay choke opening speed. If you look at the Preludes with the dual Keihin sidedraft carbs, they have a diagnostic system built in, they also have things like a mass airflow sensor, etc,that the three g doesn't have. it's basically twice the headache plus twice the vacuum lines. If one carb goes bad they both have to be replaced, as one controls the other. It didn't do much good though as those dual side drafts never worked right from day one. Thats why you don't see many of the cars with the dual carbs on the road, they died and couldn't be fixed. You may have heard people talk about Ferrari's having possessed carbs, they don't have anything on one of these systems when it goes bad.

[carotman]

It's a good thing Canadian 86-87 cars don't have an O2 or these frequency valves A and B. One less thing to go bad.

Good luck with your project. These cars would benefit from a certain diagnosis tool.

[Dr_Snooz]

don't forget the engine senses rpm, and there's an electronic switch built into the cluster that tells the car when it's going over 5 miles an hour, this changes the status of the inputs and outputs, the problem with doing this, is the controller doesn't have sensors for everything, it's a Frankenstein system of vacuum controls and electrical controls that don't actually interface with each other in any way, in other words one system doesn't know what the other is doing, eg. the air jet controller, modifies mixture by vacuum controls depending on barometric pressure, it can be completely screwed up, and the control unit doesn't know. This is why it's so hard to get these systems right, two independently operating systems not in communication with each other but causing interaction between the two, depending on what they are doing. the ECU doesn't have all digital outputs either, the valves that control the mixture don't work on straight DC, it's a square wave, the control box changes the frequency of this square wave to modify the mixture, hence the name frequency control valves, you have other things also going on, such as the EFE heater, it has an independent control circuit and heats the mixture going through it on start up, also the system that controls air intake temp is completely vacuum controlled , it can influence the mixture, there is also an air intake sensor that can switch in a resistor to delay choke opening speed. If you look at the Preludes with the dual Keihin sidedraft carbs, they have a diagnostic system built in, they also have things like a mass airflow sensor, etc,that the three g doesn't have. it's basically twice the headache plus twice the vacuum lines. If one carb goes bad they both have to be replaced, as one controls the other. It didn't do much good though as those dual side drafts never worked right from day one. Thats why you don't see many of the cars with the dual carbs on the road, they died and couldn't be fixed. You may have heard people talk about Ferrari's having possessed carbs, they don't have anything on one of these systems when it goes bad.

It doesn't have to be perfect. If he does nothing more than wire up the easy controllers it will be a million times better than nothing. He's spent the last couple weeks tracking down little electric carb controllers that have fritzed. Most of those will be pretty easy, I'd think. He can get more creative for the other stuff. A vacuum sensor would be relatively easy to create, as would a temp sensor. He could wire off the pulser in the speedo for speed, etc. I think it would be very do-able.

My only concern would be that by the time you finish working the bugs out of it, you would have spent about as much time as it would take to swap to FI.

Good luck and definitely keep us posted.

[lostforawhile]

It doesn't have to be perfect. If he does nothing more than wire up the easy controllers it will be a million times better than nothing. He's spent the last couple weeks tracking down little electric carb controllers that have fritzed. Most of those will be pretty easy, I'd think. He can get more creative for the other stuff. A vacuum sensor would be relatively easy to create, as would a temp sensor. He could wire off the pulser in the speedo for speed, etc. I think it would be very do-able.

My only concern would be that by the time you finish working the bugs out of it, you would have spent about as much time as it would take to swap to FI.

Good luck and definitely keep us posted.I appreciate the effort, but these carbs are just not worth it, once any of these electronic keihins go bad, they are just about impossible to fix, I've got good diagnostics charts and i've been messing with them for over 25 years and I still end up throwing up my hands trying to fix the things. the older they get the harder they will be to fix, plus a lot of critical pieces are now discontinued for them

[Buzo]

I am new to honda's cars and all I know about them is what I can read in the service manual and what I have measured myself. I appreciate you guys telling me your experiences.

I don't intend to mess with the controllers and modify what the actuators actually do to the engine.

I just want a start point when you get a failure. I.e "the car started to stumble this morning, Is there a code in my OBD?" Yes - Good! No - Freakin project didn't work!

This is the PCB design so far. I added some LEDs to actually see if at least they are getting activated. As you pointed out there will be PWM and Analog signals that the sight will not be able to capture, but that's what the microprocessor is for.

http://img141.imageshack.us/img141/7947/printedcircuitboard.png (http://img141.imageshack.us/i/printedcircuitboard.png/)

In the other hand, monitoring signals is what I do for a living. So running wires to/from inputs/outputs is the easier part for me. The difficult part is learning what you guys have learned in all those years enjoying these cars.

There is no dead line to accomplish this project, I will be doing it slowly. I plan to first "learn" what a good O2 sensor does and then make it fail by disconnecting it or making a short. Then use that information in my PIC code.

[lostforawhile]

if it helps, Dr Snooze scanned the entire electrical troubleshooting manual, it's on the 3geez wiki, it's for 89 so most of it is right for the earlier years, one difference is all the cars, cruise or not have a clutch switch, on later models it's connected to an interlock, on earlier ones, it's not connected to the interlock, but I believe it's an input to the controller, I'll need to do a continuity test between the pink wire on the switch and the input plug of the control module

[Dr_Snooz]

Subscribed.

[Buzo]

I appreciate the effort, but these carbs are just not worth it, once any of these electronic keihins go bad, they are just about impossible to fix, I've got good diagnostics charts and i've been messing with them for over 25 years and I still end up throwing up my hands trying to fix the things. the older they get the harder they will be to fix, plus a lot of critical pieces are now discontinued for them

I fully understand what you are saying here. And it may change the whole scope of my project. I just would like to do these final comments.

To be honest with you guys, when I see the check engine on in my other cars, I take them to the dealer.

But as far as I know, you can't do the same with these cars because they will say it is not worth it. So that was the main Idea behind this project. No need to take it to the dealer, a way to run the diagnostic yourself and based on real data, decide what to do. (The cause of white smoke in the muffler is a blown head gasket? Or a coolant leak in the carburetor's base? With this question I mean that there may be a hard fix (head gasket), and may be an Easy fix (Carb base) for the same sympthom. So a right diagnostic may be a huge difference). I learned it in this forum :)

Of course there will be no magic in a basic OBD, you still would need some troubleshooting skills to find the root cause of the blinking code.

Thanks again for your input. That was the purpose of posting the idea first.

[carotman]

This is an awesome project!

I know you'll need to monitor the idle solenoid, air temp sensor, EGR.

[Buzo]

With this PCB I can monitor 4 analog signals at the same time.
The board communicates directly to my laptop's serial port, so I will be plotting whatever data i get in excel.

I'm thinking in the Air temperature, Coolant temperature and oxigen sensor, since these signals are used by the ECU to make decisions.
With this information I can set working limits and later, rise alarms if out of such limits.

Here is the PCB in theory:

http://img210.imageshack.us/img210/1070/adcpcb.png (http://img210.imageshack.us/i/adcpcb.png/)

And here is the same PCB, but in the real word:

http://img585.imageshack.us/img585/4710/pcbl.jpg (http://img585.imageshack.us/i/pcbl.jpg/)

Tomorrow will hook it up to the car and see what happens.

[lostforawhile]

With this PCB I can monitor 4 analog signals at the same time.
The board communicates directly to my laptop's serial port, so I will be plotting whatever data i get in excel.

I'm thinking in the Air temperature, Coolant temperature and oxigen sensor, since these signals are used by the ECU to make decisions.
With this information I can set working limits and later, rise alarms if out of such limits.

Here is the PCB in theory:

http://img210.imageshack.us/img210/1070/adcpcb.png (http://img210.imageshack.us/i/adcpcb.png/)

And here is the same PCB, but in the real word:

http://img585.imageshack.us/img585/4710/pcbl.jpg (http://img585.imageshack.us/i/pcbl.jpg/)

Tomorrow will hook it up to the car and see what happens.the air temp sensor isn't an analog signal,it's just on and off, and it doesn't even communicate with the control box, it switches a resistor in and out to control the choke opening speed, the temp sensor only connects to the gauge, the o2 sensor will be a narrow band signal. i'll have to look at the wiring diagram, but I believe the other temp sensor on the block only is a switch for some of the emissions valves

[Buzo]

the air temp sensor isn't an analog signal,it's just on and off, and it doesn't even communicate with the control box, it switches a resistor in and out to control the choke opening speed, the temp sensor only connects to the gauge, the o2 sensor will be a narrow band signal. i'll have to look at the wiring diagram, but I believe the other temp sensor on the block only is a switch for some of the emissions valves

Of course they are connected to the control box.
Look at this page (11-87) of the service manual.
At least these are the ones I am referring to.

http://img547.imageshack.us/img547/7831/page1187.png (http://img547.imageshack.us/i/page1187.png/)

The ECU makes lots of desicions based on the coolant and air temperatures.
Here is just one example.

http://img18.imageshack.us/img18/8150/62907812.png (http://img18.imageshack.us/i/62907812.png/)

I spent too much time watching the footbal games, so very little progress today :)

[lostforawhile]

Of course they are connected to the control box.
Look at this page (11-87) of the service manual.
At least these are the ones I am referring to.

http://img547.imageshack.us/img547/7831/page1187.png (http://img547.imageshack.us/i/page1187.png/)

The ECU makes lots of desicions based on the coolant and air temperatures.
Here is just one example.

http://img18.imageshack.us/img18/8150/62907812.png (http://img18.imageshack.us/i/62907812.png/)

I spent too much time watching the footbal games, so very little progress today :)that must be the 88-89 the one i have shows no temp input to the ecu

[carotman]

I know the ECU also checks something to activate the Idle solenoid valve.

For some reason, my ECU doesn't activate it anymore :(. I had to ghetto rig something to bypass it.

[Buzo]

Here is the first data logged.

You can see how the TA changes resistance accordingly to the door position. If its open, lets hot air enter and the resistance and voltage increases.
If its closed, lets cold air enter, the resistnce and voltage decreases.


The 5V at the end is because I disconnected the white connector from the TA sensor. If I make a short, of course it will be 0V. But I don't want to do that, he-he

For my diagnostics purposes, I can monitor that the sensor changes above and below 2 Volts. Or I can put wider open limits, "as long as it is not at +5V or 0V then the sensor is OK".



http://img198.imageshack.us/img198/3378/talog.png (http://img198.imageshack.us/i/talog.png/)

Does it make more sense now?

[Buzo]

O2 sensor data log

Need to elaborate more in this one, like logging the signal during a trip.
Just fired up my car and waited until warmed up then started acquiring data.
The las three peaks are some 3000 RPMS-5 seconds-lenght accelerations and the 0V at the end is when shut the car off.

http://img819.imageshack.us/img819/9991/68041108.png (http://img819.imageshack.us/i/68041108.png/)

[AccordB20A]

thats neat as! good work

[88Accord-DX]

Oscilloscope readings are pretty neat on diagnostics. Looks like you have a interesting project going on. Good luck with it, I'll stay tuned in. :naughty:

[forrest89sei]

Cool Project Carbs And Computers Together could be good?? WOW!

[2ndGenGuy]

This is super badass! I've been poking around this thread every once in a while since you started it. It's looking really awesome so far! I love the flow from concept to prototype board! This is by far the coolest DIY stuff, IMO. Something about this is more exciting to me than turbos and horsepower and all that stuff!!

One thought that popped into my head was to T into vacuum lines at certain points with some MAP sensors (if they would really even be MAP sensors anymore), and monitoring vacuum at thermovalves to see if they are opening at proper coolant temps. You could use sensors to check vacuum at any of the crazy 130483948 lines in the carb system on the fly to monitor if things are getting vacuum when they should be... Just an idea, anyways. :)

What do you do? Must be some kind of electrical engineer? Or just a hobbyist?

[Buzo]

This is super badass! I've been poking around this thread every once in a while since you started it. It's looking really awesome so far! I love the flow from concept to prototype board! This is by far the coolest DIY stuff, IMO. Something about this is more exciting to me than turbos and horsepower and all that stuff!!

One thought that popped into my head was to T into vacuum lines at certain points with some MAP sensors (if they would really even be MAP sensors anymore), and monitoring vacuum at thermovalves to see if they are opening at proper coolant temps. You could use sensors to check vacuum at any of the crazy 130483948 lines in the carb system on the fly to monitor if things are getting vacuum when they should be... Just an idea, anyways. :)

What do you do? Must be some kind of electrical engineer? Or just a hobbyist?


Oh thanks for your comments & ideas. I only hope it helps to track down failures in this complex system.

I am electrical engineer and I have been always doing electronic stuff as a hobby, like transforming a simple $20 USD remote controlled car into a robot that can follow a line drawn in the floor, etc. So now that I got this real car full of sensors, its time to do something more beneficial.

But going back to the project, tomorrow will be an exciting day, I will permanently hook up the Microprocessor to the ECU and log all digital signals at the same time during different driving conditions.

After I understand better how things interact, I can start writing the code that will let me know when "something should be activated at this time and it was not".

This is how the Acquisition board has evoluted in these two weeks:
I added the screw blocks to make the connections to the ECU and some resistors below to be able to reduce the 12V signals to 5V and protect the micro.

http://img232.imageshack.us/img232/4395/imagen232h.jpg (http://img232.imageshack.us/i/imagen232h.jpg/)

[Buzo]

...thats neat as! good work

...Oscilloscope readings are pretty neat on diagnostics. Looks like you have a interesting project going on. Good luck with it, I'll stay tuned in.

...Cool Project Carbs And Computers Together could be good?? WOW!

Not sure how to do multiple quotes here, but I thank you for your comments, This thing is working better than I expected.

We will know by tomorrow the secuence of the star up, from the time the key is open, until when the car is fully warmed up.

[Dr_Snooz]

Off the hook!

[Buzo]

Made one 5 feet long harness, Labeled each wire with the name of the signal it will carry.

http://img824.imageshack.us/img824/9122/1imagen220.jpg (http://img824.imageshack.us/i/1imagen220.jpg/)

Decided to modify my ECU instead of the car's harness, so if I screw up something, I just buy another ECU.

http://img651.imageshack.us/img651/2332/2imagen221.jpg (http://img651.imageshack.us/i/2imagen221.jpg/)

Each cable is soldered to the ECU, An advise if you ever solder something, put some solder to the wire and to the PCB, then join them and apply heat with the iron. It will allow the solder to reflow better, also, this way there is no need of a third arm to hold the solder while you are holding the iron and the wire.

http://img534.imageshack.us/img534/4761/3imagen223.jpg (http://img534.imageshack.us/i/3imagen223.jpg/)

http://img141.imageshack.us/img141/6247/4imagen224.jpg (http://img141.imageshack.us/i/4imagen224.jpg/)

http://img132.imageshack.us/img132/6387/5imagen225.jpg (http://img132.imageshack.us/i/5imagen225.jpg/)

How the PCB looks after the wires were soldered

http://img703.imageshack.us/img703/254/6imagen228.jpg (http://img703.imageshack.us/i/6imagen228.jpg/)

http://img152.imageshack.us/img152/5991/7imagen229.jpg (http://img152.imageshack.us/i/7imagen229.jpg/)

Putting together the ECU again.

http://img27.imageshack.us/img27/8201/8aimagen230.jpg (http://img27.imageshack.us/i/8aimagen230.jpg/)

There is plenty of room for the wires below the PCB

http://img34.imageshack.us/img34/4034/9aimagen233.jpg (http://img34.imageshack.us/i/9aimagen233.jpg/)

[Buzo]

Cont'd...

Had to cut a hole in the side of the ECU.

http://img513.imageshack.us/img513/1963/10imagen234.jpg (http://img513.imageshack.us/i/10imagen234.jpg/)

http://img151.imageshack.us/img151/6792/11imagen239.jpg (http://img151.imageshack.us/i/11imagen239.jpg/)


The modifyed ECU already connected to the OBDZ.

http://img515.imageshack.us/img515/2268/12imagen240.jpg (http://img515.imageshack.us/i/12imagen240.jpg/)

Installed back in the car.

http://img820.imageshack.us/img820/8808/13imagen242.jpg (http://img820.imageshack.us/i/13imagen242.jpg/)

[Buzo]

A quick note here: If I ever finish debugging this OBDZ, I will buy a yunk ECU and its matting connectors, so the OBDZ can be installed quickly in a car, get the code (s) and then put everything back to normal.
I soldered directly to the ECU in mine just because I din't want to go to the JY today. Football time!

[lostforawhile]

i'll sell you mine for a few bucks plus shipping with the connector, i have no use for it with the SU's

[Buzo]

This is what the book says about the cranking leak solenoid valve.

http://img829.imageshack.us/img829/9889/crankingsol.png (http://img829.imageshack.us/i/crankingsol.png/)

And this is what actually happens in the car during start up.

http://img199.imageshack.us/img199/5522/crankingleaksolvalve.png (http://img199.imageshack.us/i/crankingleaksolvalve.png/)

So my code will be:

Ign ON, Cranking Sol ON
Start ON, Cranking Sol ON
Start OFF, Cranking Sol OFF (after a 1 sec delay)

Anything else will cause the LED to blink and point you to that.

[Buzo]

This is what the book says about these O2, Ta and TW sensors

http://img19.imageshack.us/img19/1739/64889658.png (http://img19.imageshack.us/i/64889658.png/)

http://img5.imageshack.us/img5/9296/73079415.png (http://img5.imageshack.us/i/73079415.png/)

http://img59.imageshack.us/img59/6904/97038034.png (http://img59.imageshack.us/i/97038034.png/)

And this is what I captured.
The temp when I measured these signals this morning was 10 C.

http://img708.imageshack.us/img708/5652/tempsn.png (http://img708.imageshack.us/i/tempsn.png/)

Easy to put pass/fail limits!

[Buzo]

i'll sell you mine for a few bucks plus shipping with the connector, i have no use for it with the SU's

Sure! I'll let you know when I'm ready, and thanks for the offer.

[Buzo]

Here is the EFE relay information.

First, the book information and below the ECU Output measured in the car.

http://img218.imageshack.us/img218/3315/efeall.png (http://img218.imageshack.us/i/efeall.png/)

[Buzo]

This picture is amazing. It shows what happens in the first 6 to 7 seconds during start up.


http://img710.imageshack.us/img710/695/secuence.png (http://img710.imageshack.us/i/secuence.png/)

I think I finished capturing the Digital signals, I need to start capturing the frequency solenoids and control valves. So I need to do some more code for the microprocessor.

[Buzo]

The theory belonging to below post.

http://img33.imageshack.us/img33/9095/vacuumsw.png (http://img33.imageshack.us/i/vacuumsw.png/)

It makes sense the Vacuum B gets activated first, since it's calibated at a higher vaccum compared to the Vacuum Switch A.

[Buzo]

Here is a picture of the user interface, written in LabView.
At the end, each LED will say the name of the sensor/solenoid and will have a second LED with the expected status, so visually one can compare if a Solenoid should be off/on, blinking or something else in a given time.

This is if a laptop with a serial port is available, but the OBDZ will have one single LED indicating the problem, so no computer is needed.

By the way, Would you guys mind if I use your 3Geez logo as background in my software? It will look better than the default gray.

http://img209.imageshack.us/img209/1264/midway.png (http://img209.imageshack.us/i/midway.png/)

I have logged lots of data during my trips to my work and back home. So I plan to keep explaining every single actuator in the car, so anybody with a multimeter can do the diagnostic of a failure.

As I said, I am currently working to determine frequency and PWM values for the control solenoids...

[Buzo]

Continuing with some theory, here is the Primary Slow Mixture Cut-Off Solenoid Valve.

The book explains better than anybody the function of this solenoid. Also, if it is working fine, it means all the needed inputs are working OK as well.

http://img707.imageshack.us/img707/700/cutoff.png (http://img707.imageshack.us/i/cutoff.png/)

[Buzo]

Just to confirm what the service manual and I just said...

http://img641.imageshack.us/img641/8797/cutoffon.png (http://img641.imageshack.us/i/cutoffon.png/)

[Buzo]

Just one more... (for today)

This is the Oxigen Sensor. I increased the acquisition speed, so now it reflects better whats happening.
As long as it is at .5 average, the car and the systems are well carbureted, and should pass the smog test!

I have always wondered if a guy with a non-stock carburetor can use the O2 signal to make the carburation adjustments. Why not?

http://img43.imageshack.us/img43/7751/o2highspeed.png (http://img43.imageshack.us/i/o2highspeed.png/)

[integratuner77]

Hey man I just wanted to say great work. Coming from an engineering view this is awesome! Absolutely an ingenious idea and very well executed. Thank you for the constant updates.

[Buzo]

Couldn't resist and made another run with the Solenoid and Control valves connected to the OBDZ.

And just because I found this graph very accurate I think it is worth to post it.

http://img718.imageshack.us/img718/5597/freqsolaandb.png (http://img718.imageshack.us/i/freqsolaandb.png/)

[carotman]

I don't see a problem if you use the 3geez logo as long as you continue your project till the end :D

I will buy one of your diagnosis boards for sure.

You should make the thing "configurable" so one can disable sensors depending on where they live.

Like I said, Canadian Accords didn't get any O2 sensor for 86-87. This means the frequency solenoid A and B that alter mixture aren't there.

[Buzo]

Hey man I just wanted to say great work. Coming from an engineering view this is awesome! Absolutely an ingenious idea and very well executed. Thank you for the constant updates.

Thank you for your comment. I think I got here a little too late, but still all this information might be valuable to understand any other fuel system.
You may not be controlling the air suction in a FI system, but the injector's open/close time. At the end it is the same thing if one has the bases.

[Buzo]

I don't see a problem if you use the 3geez logo as long as you continue your project till the end :D

I will buy one of your diagnosis boards for sure.

You should make the thing "configurable" so one can disable sensors depending on where they live.

Like I said, Canadian Accords didn't get any O2 sensor for 86-87. This means the frequency solenoid A and B that alter mixture aren't there.

OK great! Thank you. Hopefully somebody has the 86-87 Service manual around here, it will help to understand the differences, but if not, as simple as you said, put a way to dissable inputs and outputs, like configurable switches in the PCB to select options like automatic/manual, etc, O2 yes/no and so on.

I will finish posting the control valves graphs I captured today, and the next step will be to cause controlled failures in the systems and see what happen, then find a way to catch it.

[lostforawhile]

Just one more... (for today)

This is the Oxigen Sensor. I increased the acquisition speed, so now it reflects better whats happening.
As long as it is at .5 average, the car and the systems are well carbureted, and should pass the smog test!

I have always wondered if a guy with a non-stock carburetor can use the O2 signal to make the carburation adjustments. Why not?

http://img43.imageshack.us/img43/7751/o2highspeed.png (http://img43.imageshack.us/i/o2highspeed.png/)

it's best to use a good air fuel meter and a wideband sensor for non stock carb setup, this is a very simple narrow band sensor, it's also not heated, so it's going to be inaccurate for a few minutes until it reaches operating temp. those sensors are designed to run almost red hot, this is the reason for modern heated sensors, the electric element heats the sensor immediately

[Buzo]

In case you guys wonder how the pass/fail decisions are going to be made, I'm including here the concept of the flow chart I have (still) in my mind.

The goal is to use more than one signal to define the current state of the car, so if one is missing the others will tell the OBDZ the truth.

So multiple codes could appear, each one separated with a LED off for 2 seconds. When only the the ignition is present the LED wil be blinking really quick so you'll know it is thinking, instead of a steady (software cycled?) LED.

http://img3.imageshack.us/img3/6025/page1nd.png (http://img3.imageshack.us/i/page1nd.png/)

http://img214.imageshack.us/img214/6784/page2r.png (http://img214.imageshack.us/i/page2r.png/)

http://img203.imageshack.us/img203/3783/page3m.png (http://img203.imageshack.us/i/page3m.png/)

[Buzo]

I have found a couple of real failures in my car so far. I should get my LED blinking if the project were complete at this time :)

1) Idle Boost Solenoid ON and OFF, so the idle speed rises to 1100 and back to 900 once per second. I have a problem with the Park shift indicator, it sometimes won't turn on after a trip. So it may be affecting it.

Its hard to notice but the parking signal has double line when changing from 5 to 0V. That's exactly when the false contact ocurrs.

http://img703.imageshack.us/img703/7969/failuren.png (http://img703.imageshack.us/i/failuren.png/)

2) I can't read the frequency of the ignition coil, even though the RPMS in my instrument panel is reading OK, the signal is changing too fast so can't measure the frequency. I know I have problems with the coil, so its time to buy a new one.

http://img222.imageshack.us/img222/3268/ignitioncoilf.png (http://img222.imageshack.us/i/ignitioncoilf.png/)

Those two issues are not a job stopper, so i'll keep going with the project while I fix them.

[2ndGenGuy]

I'm still following. This is totally badass. :)

[Buzo]

Enough testing!! I got enough information to complete this project. I know when a valve/sensor should be ON and when should not.

I felt some inspiration today and completed the front page of the software.
Sorry didn't resized the screenshots, but will lost some resolution.

http://img30.imageshack.us/img30/1884/fp1.png (http://img30.imageshack.us/i/fp1.png/)

http://img340.imageshack.us/img340/1167/fp2.png (http://img340.imageshack.us/i/fp2.png/)

http://img211.imageshack.us/img211/9112/fp3.png (http://img211.imageshack.us/i/fp3.png/)

[integratuner77]

Nice work on the VI. Its all coming together very well. I'm really interested in how this will turn out. I love all the data your collecting and find it very interesting. Keep it up.

[Buzo]

Nice work on the VI. Its all coming together very well. I'm really interested in how this will turn out. I love all the data your collecting and find it very interesting. Keep it up.

Hey, looks like you have some knowledge of Lab View, Great. I'm in the most exciting part of the code right now, making the pass fail criterias. Right now I am just asking If the signals are changing through the time. If all signals are found then I can start making smarter pass/fail decisions.
.

[Dr_Snooz]

I'm in the most exciting part of the code right now, making the pass fail criterias.

Oh yes, white-knuckled excitement that coding!

This project is awesome and really coming along quickly. It's nice to see how you think through each piece of it, gather data, develop a plan of attack and then execute. Awesome!

[Buzo]

Here the Final PCB.
I added one diode to each input to isolate them from each other. I found that was the cause of the failure in my Idle Solenoid.

Migrated to a 40 pins microprocessor.

I don't need a LED for each input, there will be some heat build up in this thing if I put 33 LEDs and they turn on at the same time. So the LEDs in the software are enough.

I will use the Software to tell the OBDZ if the car is standard/auto, with/whithout O2, AC/No AC, etc. 33 inputs were not enough to put switches in the PCB.

I will build the PCB tomorrow, test it and install it below the drivers seat.
Then will debugg the software and when done, just a matter of translating from LabView to Assembler :)

http://img28.imageshack.us/img28/5743/finalpcb.png (http://img28.imageshack.us/i/finalpcb.png/)

[Buzo]

This is the end of the project... from the hardware standpoint.
Software is the easiest part, I need a couple of days to finish it all.

This thing sends all the ECU signals, one at the time through the serial port. The software in the PC receives the signals, and writes them down to a file in the hard drive at the same time that turns led's ON and OFF in the main screen depending of the status of the inputs received.:flash:


http://img64.imageshack.us/img64/1690/finalpcb.jpg (http://img64.imageshack.us/i/finalpcb.jpg/)

[87roach]

You're doing some really great work here man, keep it up!

[Buzo]

Thanks for your comments, I have a few more pictures taken today as I installed it in the car.

Replaced the smaller microprocessor with a bigger one. For the first time I will be able to log everything that happens in the car during the same drive.


http://img403.imageshack.us/img403/1021/oldandnewguys1.jpg (http://img403.imageshack.us/i/oldandnewguys1.jpg/)

http://img217.imageshack.us/img217/672/oldandnewguys2.jpg (http://img217.imageshack.us/i/oldandnewguys2.jpg/)

http://img714.imageshack.us/img714/3756/newguyinstalled.jpg (http://img714.imageshack.us/i/newguyinstalled.jpg/)

[Dr_Snooz]

You still have the stock stereo???? Does it work at all?

[Buzo]

You still have the stock stereo???? Does it work at all?

The radio works fine, I haven't tryed the cassette player, because I don't have a tape anymore! I usually use a FM transmitter with my ipod (that's why the ligther is not in place).

[Buzo]

After several trys I concluded that the best way to display results is through the graphs similar to what I have been posting in this thread.

And that was because the signals change through the time, so its hard to track or count how many times each signal changes.

And this is how it looks:


1.- Set up. Select your serial port, select if you want the data saved into a txt file. A 20 minutes log weights about 680 k.
Press start to begin. If you see the data received in the format shown, you are all set, if not, a 10 seconds timeout will occur.

http://img40.imageshack.us/img40/7679/setupwk.jpg (http://img40.imageshack.us/i/setupwk.jpg/)

2.-Inputs. Each signal has a excpected waveform to the left. This waveform was taken during a 20 minutes ride in my car, so it may not be perfect, but you will get the idea of what should happen in each input.

http://img521.imageshack.us/img521/8190/inputs.jpg (http://img521.imageshack.us/i/inputs.jpg/)

3.-Outputs. Same as inputs, my car's read signals as reference.

http://img14.imageshack.us/img14/4721/outputs.png (http://img14.imageshack.us/i/outputs.png/)



Next step is to talk to a neighbor of mine that actually has a couple of 3geez
to test the software and OBDZ in a car different than mine.

Then complete the assembler code to emulate the OBD system with the flashing LED the FI cars have.

The graphs shown in the screenshots above were taken in a 10 minutes ride around the neighborhood, max speed 40 MI, and you will notice there are some graphs missing. Well, I need to dig into that.

[Buzo]

I need to fix those inputs that look flat in below post, for example the solenoid responsible for the bubbling noise. I know that signal is there, but for some reason is not being detected, its a matter of rewiring those flat signals to known good inputs in the PCB.

Please stay tunned because during the weekend I plan to reproduce the failures I found in the car when I first bought it, just to see how this diagnostics tool could help me.

1.-Vacuum leak in the Air Intake door actuator
2.-Vacuum leak in the thermovalve actuator
3.-Frequency solenoid valve C hose pinched off
4.-General Idle system missadjustment
5.-Fuel flooding... But we have the fuel odor to detect this one, so I better don't mess with it for this time.
6.-Ignition coil signal to the tacho. Yeah, had no chance to replace the coil yet.

[2ndGenGuy]

That's so badass! Seriously mad skillz here. Your PCB looks awesome. What kind of processor is that that you use for something like this?

[Dr_Snooz]

After several trys I concluded that the best way to display results is through the graphs similar to what I have been posting in this thread.

And that was because the signals change through the time, so its hard to track or count how many times each signal changes.

And this is how it looks:


1.- Set up. Select your serial port, select if you want the data saved into a txt file. A 20 minutes log weights about 680 k.
Press start to begin. If you see the data received in the format shown, you are all set, if not, a 10 seconds timeout will occur.

2.-Inputs. Each signal has a excpected waveform to the left. This waveform was taken during a 20 minutes ride in my car, so it may not be perfect, but you will get the idea of what should happen in each input.

3.-Outputs. Same as inputs, my car's read signals as reference.

Next step is to talk to a neighbor of mine that actually has a couple of 3geez
to test the software and OBDZ in a car different than mine.

Then complete the assembler code to emulate the OBD system with the flashing LED the FI cars have.

The graphs shown in the screenshots above were taken in a 10 minutes ride around the neighborhood, max speed 40 MI, and you will notice there are some graphs missing. Well, I need to dig into that.

Now I have a headache...

[Buzo]

Now I have a headache...

Yeah, I know. But I tried different things like add a PASS/FAIL word to each signal, and none seems to work better than the waveforms.

Actually I want to thank you for scanning and uploading the service manual, without it this work could not be possible and the interaction of the carb'd fuel system would remain un-comprehended.

[Buzo]

That's so badass! Seriously mad skillz here. Your PCB looks awesome. What kind of processor is that that you use for something like this?

It is called PIC 16F877. 33 inputs, Analog to digital converter, serial communication port, perfect for this application.

This project itself could be considered out of the scope of this forum, that's why I didn't want to add anything related to the build of the PCB to this thread, I would bored you guys to death.

I am thinking seriously in aborting the blinking led capability. I mean, a laptop with a USB to serial port adapter is available almost anywhere. So I think I can close this project after I run my failures simulation this weekend.

[Buzo]

One good new and one bad new

Good one:
I was able to induce failures to my car, and detect them with my system.


Bad one:
I don't recal exactly which action produced which failure.

For example in the chart below I was able to make my system too rich, but I disconnected several things during the experiment that I am unsure which one produced the failure.

So I need some more time to come up with a relationship between a disconnected hose, and its effect in the car.

http://img820.imageshack.us/img820/7219/o2rich.jpg (http://img820.imageshack.us/i/o2rich.jpg/)

[Buzo]

I just found that its a pain in the butt to connect the laptop to the OBDZ everytime, so I am re-considering putting the Diagnostics LED back.

I have made good modifications latelly, I am able to measure speed and engine rpms and send that information to the Laptop.

Will update my post soon.

[2ndGenGuy]

It is called PIC 16F877. 33 inputs, Analog to digital converter, serial communication port, perfect for this application.

This project itself could be considered out of the scope of this forum, that's why I didn't want to add anything related to the build of the PCB to this thread, I would bored you guys to death.

I am thinking seriously in aborting the blinking led capability. I mean, a laptop with a USB to serial port adapter is available almost anywhere. So I think I can close this project after I run my failures simulation this weekend.

You have a link to another forum where all the "boring" stuff is? I love that stuff! Feel free to post it here! I think it would be great!

[Buzo]

I can say I finished my project.

As its older brothers the OBDI and OBDII, my OBD0 only detects failures related to the emissions control. It autodiagnoses the ECU and reports out if one output is bad because there are missing inputs, or due to an internal ECU failure (just like the FI one).

It is not able to find vacuum leaks, or why your engine is stalling.

However, I learned how all the sensors and actuators interact with the engine, I whish I have met one of these cars when new. The concept itself is, as I said before, a dream come true. In the old days of the carbed cars, we all wanted an automatic throttle control, or an idle boost to avoid adjusting the idle too high so the engine doesn't die when in "D", and a lot of other nice features.

Of course I am not done with monitoring signals in the car, I'll keep adding external sensors in strategic places to cover more failures than the ECU-related ones.

This is the last screen I added, it is really nice to see your speed/rpms in the screen of the computer. Someday we could put a monitor inside the instrument panel and simulate all the needle indicators, costomize them, change them to digital, interchange positions, play music, etc.

Thanks for your comments and opinions and thanks for reading this thread. More to come yet!

http://img7.imageshack.us/img7/8043/lastonewy.jpg (http://img7.imageshack.us/i/lastonewy.jpg/)

[A20A1]

This is an incredible tool

Do you plan to hook up a vacuum/pressure sensor?


I wonder if Honda engineers ever made something like this to test their own system when producing the 3G




One good new and one bad new

Good one:
I was able to induce failures to my car, and detect them with my system.


Bad one:
I don't recal exactly which action produced which failure.

For example in the chart below I was able to make my system too rich, but I disconnected several things during the experiment that I am unsure which one produced the failure.

So I need some more time to come up with a relationship between a disconnected hose, and its effect in the car.

http://img820.imageshack.us/img820/7219/o2rich.jpg (http://img820.imageshack.us/i/o2rich.jpg/)

Which hoses? Was it one of the A,B,C lines?
Is there any difference between cars sold in Mexico and ones sold in the US? Not all 3G's out there came with the same heap of emission controls the US cars did.