Carb problems (engine stalling and dying): help testing & fixing

[lionel]

I have read a number of very interesting posts showing impressive knowledge and skills, but I can't find out what's wrong with my car...

Car:
88 Accord 3D DX, 235kmi, orig ignition fuel pump and carb except for air vent cut off valve, choke cap heater and few vacuum hoses replaced. Fuel filters are brand new, coolant is fine.

Problems:
I am experiencing engine hesitation, which quickly ends up in the engine stalling, either when warming up (especially after sitting in the cold all day) or when hot but it seems to happen in cold whether (less than 10C). Other symptoms:
- heavy smoking when cold
- very poor mileage (200 mi on 1 tank in city driving)
- rough idling @900 RPM when cold

I had also been experiencing before this pb starts occuring, rough idling (cold and hot engine) during summer time, with poor city driving mileage but highway driving mileage fine. I made a few checks last we and found out major vacuum leaks:
- deteriorated plug cap on vacuum port #20
- leak in hose #7 to air jet controller
- leak in #14 to powervalve

I fixed everything, results was nice hot engine idling but it didn't solve the hesitationand engine dying problem, so I spent a bunch of hours testing (according to FSM) and trying to find out where the problem was, with no results.

Results of some testing:
Apparently there are a bunch of stuff not working properly on my car... The question is what do I need to fix to get the car back to driveable conditions?

1) Fast idle unloader: diaphragms are working fine, but it does not get the vacuum from hose #18. Hose 18 has no leak. My understanding is that it shhould get vacuum trough the choke opener but I don't get any vacuum on the outside port of the choke opener. As a consequence, I don't get eitehr any vacuum on hose #19 to the unloader. Thermovalve A is working fine.

2) Choke opener: I don't get the tab A seating all the way on the carb as described per the FSM when engine is hot. If I pull vacuum on the outside port the rod will go bckwd but won't stay. Vacuum is not holding (engine on and off), is it normal?

3) Throttle controller: doesn't hold vacuum but: when air cleaner if off and vaccum ports 8 and 33 blocked, there is enough vaccum to hold the rod back. When I put back the air cleaner, it does not hold it anymore and I get high rpm.

4) Thermovalve C (carburator secondary) is always open, so I blocked it, it is OK?

5) Powervalve (from hose #14) does not hold vacuum, but it seems I can hear some cliking sound

6) With the aircleaner off and the ports 8 and 33 blocked, I can hear some hissing sound (vacuum) inside the carb. Is it normal?

7) I tried to test the air control valve B (as I suspected mixture pbs), but I can't follow the FSN directions because the engoine stalls as soon as I disconnect the lower hose.

Thank you for your help/hint/advice.
Lionel

[A20A1]

#20 that whole (Auto) Idling setup is a pain... I perfer the (MANUAL) vacuum routing with #6 and the Check Valve. But the (AUTO) way has it's uses.

Hose #7 isn't to air jet controller, hose A, B, C, are the only ones that connect to the air jet. #7 goes from a vacuum port near the base of the carb, to the metal vacuum lines, and then to the black box.
- ( B, C, & #14 ) are the vacuum ports at the top rear of the carb.
- ( A ) is on the front of the carb near the Venturi Vacuum port for the Vacuum Secondary. Thermovalve C bleeds vacuum from the secondary so it doesn't get venturi vacuum when cold. It'll delay the secondary from opening some.

The choke opener will bleed vacuum through #26... but I'm not sure if it's all the time... it may depend on how far the choke opener is open. The choke opener recieves vacuum from an internal vacuum port. Did you test #18 & #26?


Sounds like your air bleeds are bleeding vacuum...
Hose #8. If the outside air temp is cold it will be closed so that the hot air door can hold vacuum. I think once it warms up they let vacuum bleed from the hot air door diaphragm and you'll get regular air flow.

I'm not sure if #33 is open when hot or cold...

Your vacuum idle control diaphgragm / throttle controller is supposed to raise the idle if vacuum drops... if #33 or #8 is causing big vacuum leaks when it shouldn't then you'll get out of control idle. If you get rid of your vacuum leak your idle controller should stabalize. It usually will remain in contact with the throttle linkage.

There is a small hole in the powervalve that lets air bleed in. But if it's a serious leak I would say get a new 'Top-Hat'... don't bother trying to replace the powervalve plunger in the top hat... it's in there near permanently and takes a bit of effort to remove. The clicking is the plunger that opens the powervalve going up and down, when vacuum drops a spring will lower the plunger opening the powervalve.

The air cleaner will muffle the sound of the carb, some hissing is normal with the carb open.



Check for vacuum leaks
Check battery cables / connections
Check Booster Venturies ( Make sure they don't wiggle. )

(1) PCV Valve
(2) Cap / Rotor
(3) Spark Plugs
(4) Fuel Filters x2

[A20A1]

Hrm... you're in France... that makes things interesting. I was basing some of my reply under the assumption you were in the US.

I'll have to look at your specific vacuum diagrams to see where there is any descrepencies.

[lionel]

thanks for the replies.

Yes I am in France, but I used to live in the US, and I brought the car back from the US to here, so it is a 88 US accord with carb and manual transmission.

I forgot to mention the venturies were fine. The throttle controler issue is kind of weird: before I removed teh air cleaner and went into testing/checking, the hot engine idling was fine. It's only when I put back the air cleaner that it started going high RPM with hot engine idling: my guess was that putting back the aircleaner was somehow weakening the amount of vacuum (because some of the vacuum gets bled through the air bleed valve in the air cleaner box when the engine is hot) not leaving enough vacuum to pull the leaking throttle controller.

Also, vacuum measurement at #20 vacuum port is about 22 in when hot and about 14 when cold. I am really concerned about what causes the engine to die, especially since this happens intermittently.

[HondaBoy]

dunno if this is it, but i've been told that the efe plate thats under the carb could be bad. mine does that shit of smoking and puttering when its cold until it warms up. i'm wanting to swap it out but i need to get a couple of new gaskets if i'm gonna do it.

[dalinxz]

PCV Valve
I guarantee thats the PCV Valve exact same symptoms I had. Change it and you will be good to go.

[lionel]

just checked the PCV Valve: pulling vacuum on it is fine, I get the plunger going off. Blowing air does block, but needs higher pressure to block that on a civic pcv valve (only one I had handy).
I road tested again the car:
when cold, I get high Ok idle for about 20 sec after starting, then it goes down to rough 700 RPM idling and after 2 mins driving, gets ok at 1400RPM.
Drove around fine, stopped the car for about 1 hour in cold wheather (3Celsius). I was able to start it fine but developped soon after the engine hesitation and dying pb.
Does anybody know what I should get at the choke opener 18 and 26 ports with engine cold and hot?
Also any help on testing the air control valve B would be appreciated.
#8 and #33 are fine, the hot air door control is working properly, and so is the air bleed valve .
BTW, does anybody know how to test the check valves in the vacuum hoses (like the dashpot check valve on hose 6 or the one on hose 8)?
venturies are fine, spark plugs also,
cap, rotor and wires are original
fuel filters are brand new
Thanks

[A20A1]

The check valves should flow in one direction but not the other. Just blow through it.
Hose #8 has two connections on one end... it's just a built in 'T' fitting.

[Cant Stop]

pcv valve u shaped hose could be bad too mine looks fine but i noticed it collapses when put on a load

[lackej1971]

The only way that I could fix the PCV tube on mine was to take 2 pieces of rubber hose and bend a piece of copper tubing and insert it into each end. Mine kept bending in half until I did this. I work at an air conditioner factory and we have these little "elbow" shaped pieces that fit perfectly for the job.

James

[dalinxz]

just change the real thing you can get it for $3-4 at a local auto parts store I got mine from Canadian Tire for $4CAD

[lionel]

Thanks to everybody.
A little bit of update: got stuck: cold engine started and stalled. Wouldn't start again.
So I checked the fuel pump as described in FSM: after 60 minutes on, I only got 145cc where I should have got (according) to FSM 760cc. Both fuel filters are brand new. I'll double check what I have right at the output of the pump.

Before I get a new pump, could anybody confirm the 760cc figure of the FSM is correct?
Thanks

[lackej1971]

Lionel,

My car was doing pretty much the same thing til I cleaned out the nasty stuff on the bottom of the float bowl in the carb. Just remove the 6 or 7 screws on top of the carb and easily lift it up. You will be able to see into the float chamber.

If it is dirty, please look up on this site what to do to clean it from there. It made a world of difference for my car.

James

[lionel]

More of an update:
- i had a little bit of air in the cooling system, and a small leak at the thermostat housing gasket. fixed it.

- i cheked the fuel pump flow right at the tank: only got 170 cc (instead of 760cc) after 60 seconds. That was with the fuel cutoff relay out and the jumper wire between terminal 1 and 2 and with a voltage at the pump of 12.05V, so it's a faulty pump. That does not explain the very poor mileage I had, but I'll fix it first. Could be the cause of the stalling and difficulties to start after stalling.

[lackej1971]

I'll almost guarantee you that it's the cause. Mine did the exact same thing and it was so nerve wracking. Hope this helped

James

[lionel]

I'll almost guarantee you that it's the cause. Mine did the exact same thing and it was so nerve wracking. Hope this helped
James

Thanks. You mean the float bowl or the fuel pump?
I removed the fuel pump yesterday. Found out the strainer was dirty.
I'll test it today and eventually will remove the tank, clean it and while I am there replace all the fuel hoses around (never done it before).

I also opened up the old rear fuel filter to check how dirty it was: a little bit of reddish/greyish residue but not too much.

Next step will be the top hat of the carb, but I need to get the gasket first. Thing is I don't have easy access to parts, but I'll make an order in januray.

I should be getting close to an end...

[HondaBoy]

i dont quite remember because its been over a year since i rebuilt the carb, but isnt there a few O rings that the top hat will need replaced along with the gasket? rebuilding mine was easy and it runs much better. i took the whole carb apart and cleaned it out. i used the how-to for rebuilding the carb thats in the how-to section.

[lackej1971]

Thanks. You mean the float bowl or the fuel pump?
I removed the fuel pump yesterday. Found out the strainer was dirty.
I'll test it today and eventually will remove the tank, clean it and while I am there replace all the fuel hoses around (never done it before).

I also opened up the old rear fuel filter to check how dirty it was: a little bit of reddish/greyish residue but not too much.

Next step will be the top hat of the carb, but I need to get the gasket first. Thing is I don't have easy access to parts, but I'll make an order in januray.

I should be getting close to an end...

Lionel,

I didn't really have to replace my gasket because the screws that held the top hat on were really a little loose to begin with. If I were you, I would just check the float bowl and see if thats the problem before you do all that other stuff. Chances are that you can make a real big difference in the car by removing any sludge from the float bowl. You don't have to disconnect all of those little linkages if you are VERY CAREFUL. What I did was take a wire clothes hanger and made a sort of hanging support for the top hat that hooked into one of the holes in the hood while I worked on it. It worked for me.

Now the fuel pump is another story altogether. 1. They are pretty expensive and 2. they can be difficult to change because of all of the hoses, but I think there is an access port under the floor board in the backseat area. It would help you to find out. IMPORTANT: If you plan on dropping the tank, 1 or 2 fuel lines will stretch really bad and keep it from coming all the way down. Also, have some way of identifying where each hose connects to BEFORE you start. I used electrical wire I.D. strips.

The fuel hose that you will have to get will probably have a red rubber braided material on the outside. Last time I checked, it was pretty expensive because it is maded especially so that the gas won't deteriorate it so quick. Not only that, but you will be surprised when you see ALL of the hoses that are on top of the tank. It is a job, but if you really want to do it, then at least you'll know that the fuel lines are good and clean.

I know these things from doing them myself. It was hard, but it was also very satisfying. Oh, one last thing. Put some anti-sieze grease on the bolts that hold your tank up when reassembling. When you are taking it down, they will probably be really rusted. Mine were and they were VERY DIFFICULT to remove. But not next time.

Hope this helps, James

[lionel]

Hello James,
thanks for the info and hints.

I was able to remove the fuel pump trough the above access hole, and did clean its strainer. I also tried to overhaul the pump as I was thinking worn brushes on the dc motor could be the cause of the bad flow/pressure of the pump. I couldn't go too far and didn't find any brush...

Are you familiar with those pumps? I took out the + wire screwed on the part of the pump inside the tank and put it back but I was wondering if there was any special coating to put on the screw and the post to prevent shorts between the + and the - trough gasoline. Indeed there is rubber protection on top of the + post and screw but it does not seem to be really waterproof.

What happens then when you fill up the tank completely?

Lionel

[lackej1971]

Hello James,
thanks for the info and hints.

I was able to remove the fuel pump trough the above access hole, and did clean its strainer. I also tried to overhaul the pump as I was thinking worn brushes on the dc motor could be the cause of the bad flow/pressure of the pump. I couldn't go too far and didn't find any brush...

Are you familiar with those pumps? I took out the + wire screwed on the part of the pump inside the tank and put it back but I was wondering if there was any special coating to put on the screw and the post to prevent shorts between the + and the - trough gasoline. Indeed there is rubber protection on top of the + post and screw but it does not seem to be really waterproof.

What happens then when you fill up the tank completely?

Lionel

Lionel,

Congrats on removing the pump the easy way. As far as overhauling the pump, I would not really want to do that. If it's giving you a problem now, it's only a matter of time before you have to replace it anyway. Go ahead and spring for a new or remanufactured pump. Peace of mind really is priceless.

I have a theory about insulating the wires, but it's ONLY A THEORY. I think that there really isn't that big a risk of blowing up the tank because of the lack of oxygen in the tank. In any case, I don't take chances with explosive gasses or materials, so I can't really say much else about that.

[lionel]

thanks. I test drove the car today, it's now running fine, including at high rpms.

Pb was dirty fuel pump strainer, and also air in cooling system due to leaking thermostat housing gasket.

I'll double check (next week) the fuel pump pressure and flow, but at least it's now working fine.

Next step is cleaning up the fuel tank, fixing the minor leaks (leaking vacuum advance diaphragm) and if necessary clean up, the float bown (involves removal of top hat of carb)

A big thank to all the contributors, and to summarize, if you experience idling/carb problems:
- double check cooling system
- check fuel system: fuel pressure and flow and if low, clean up the fuel pump strainer...

[lackej1971]

Glad to hear that you have it running good now. I am working on a solution for the excessive oil being blown into my breather. I bought a new air filter but i am not going to install it until I find a way to make the oil mist collect somewhere besides in the breather. My dad says that there should not be that much oil mist, but there is and I am even using a PCV filter.

I am thinking about making a mid-line expansion chamber so that the oil can disperse into the more open area and collect into larger molecules and drain back into my valve cover. Then the other end of the chamber will be just enough to keep the pressure from building up in the crank case.

It's just an idea for now, but I am sick of the constant oil blockage of my air filter.

James