New fuel pump has power? won't run

[AZmike]

The other day my the engine lost all power briefly several times and later wouldn't start until I banged on the fuel pump. I could hear the main relay working so I assumed the fuel pump was the problem. I drove it home and thought I had identified the problem: the main relay clicks twice (is good), the fuel pump gets +12 V for about 2 seconds, but does nothing. Thinking I have confirmed a bad fuel pump following factory service manual procedure, I order a replacement and install it.

The same thing happens now with the new pump. I pulled the new pump and it runs fine when jumped directly off the battery (powered at the connector, not just on the pump contacts). The strange thing is instead of getting + 12 V when I connect the fuel pump power connector the pump only gets 0.4 V instead of the +12 V I see when it's not connected. The only thing that I can imagine that would cause this is a frayed/damaged wire somewhere that barely flows any current. It will get the fuel pump connector to +12 V when it's not connected, but with the load of the fuel pump in the circuit there is way too much resistance due to the damage to run the pump. Has anyone seen something like this before. Any other ideas? Thanks

[LX-incredible]

I'd still check the main relay. The fuel pump wires run through the interior. Not much is exposed to possible damage or corrosion.

[stephensimmons]

Also check your ground ive had that problem twice before (even though it wasent on a honda) its possible.

[AZmike]

I've now tested the main relay three separate times. Each time it passed all three continuity tests. I followed the main relay harness tests and passed all of them as well. The final harness test involves jumping a couple of pins to run the fuel pump and that works correctly as well so the new (likely unnecessary) fuel pump is ok too. As expected the resistance in the fuel pump power wire is very low.

The pump and main relay both have good grounds. Are there others that I need to look at?

I don't have much left other than to try another main relay. Is there something that I am overlooking?

[LX-incredible]

So the fuel pump isn't running at all, not even the 2 seconds after you turn the key?

[Oldblueaccord]

Mike if you jumped the MR out and the pump runs ok that seem like its the reason to me. Let us know if you find out anything else in the meantime. It must not be staying latched in all the way or carrying enough current thru the contact.

Continuity test is very low voltage and no amps. If you test a large gauge wire and only one strand is on a lug it will test out OK but blow a breaker with a load on it. I think alotta guys used to carry a wiggie for that reason.


wp

[A18A]

llol this is funny, yesterday my car failed its fuel pump power too and left me stranded

[LX-incredible]

If one of the sensors in the distributor is screwed up the ecu won't see the engine as rotating, and won't close the main relay to activate the fuel pump. You should still see the 2 seconds when you first turn the key though.

[AccordB20A]

id re solder the main relay to be safe, it may pass voltage through it but it may fail when current is needed to make the pump work.

[AZmike]

To summarize:
The main relay clicks twice about 2 seconds apart (good). If the fuel pump is not connected I see +12V at the pump connector (good). Both the main relay and pump grounds are good (very low resistance). Once I connect the pump I see more like +0.4V (bad). The circuit can produce the correct voltage unloaded, but can't seem to pass anything close to enough current to run the fuel pump.

The main relay passes all of it's continuity tests. I just resoldered it (and had resoldered it a few years ago as a precaution). The main relay harness passes all of its tests including running the fuel pump (so the pump is good as well).

Everything passes its component-level tests, but won't work together. Very occasionally the pump will run for the 2 seconds so whatever is broken is still intermittent. I haven't tried to start the car yet since I'm still not getting consistent performance during the 2-second pressurization routine. On the day it was going bad I'd lose power briefly on average every 20 minutes of driving for just a few seconds.

Mike if you jumped the MR out and the pump runs ok that seem like its the reason to me. Let us know if you find out anything else in the meantime. It must not be staying latched in all the way or carrying enough current thru the contact.

Continuity test is very low voltage and no amps. If you test a large gauge wire and only one strand is on a lug it will test out OK but blow a breaker with a load on it. I think alotta guys used to carry a wiggie for that reason.

wp

I read up on the 'wiggy' and it looks like that would indicate if my cant't-pass-current problem is in the relay. I can hear the switches in the relay give a nice click as I test each circuit so I believe they are staying latched. A new main relay isn't much more expensive than a wiggy so I'll order one and see how it goes. Thanks for the input.

[w261w261]

I would start substituting parts of the circuit, piece by piece. If you have a wiring diagram (I have the grey Electrical Troubleshooting Manual 1989, so if you need any colors, connector or ground locations I can look them up).

First, I would unplug the fuel pump connector. I would jump from the 12v feed on relay side of the connector to the pump (1 wire). I would then jump from the ground connection on the pump's connector to a good ground someplace, and see what happens there. No change means the pump's ground probably is good. I know it tested that way, but that's the way I would start.

Next, I would jump from the output of the main relay all the way back to the fuel pump connector, to see if the problem is in the wiring load-wise. If that doesn't make something happen, keeping my long jumper back to the pump in place, I would jump out the fuel pump component of the main relay, keeping the temporary fuel pump ground wire also in place. Things have got to start working soon with this approach.

If the long jump back to the pump (with the relay still active) works, then I would find any intermediate connectors (if there are any, I haven't looked) and do the same thing. Or just take out the whole run with a new wire.

[AZmike]

Even though it would pass all of the service manual tests, the main relay was bad.

I suppose the key is to test the fuel pump for 12V with the fuel pump in the circuit. The positive lead is exposed on the back of the fuel pump connector making it easy to test whether there is power to the pump with the pump connected. Just looking for 12V at the disconnected harness may result in replacing a good fuel pump like I did.

[w261w261]

Even though it would pass all of the service manual tests, the main relay was bad.

I suppose the key is to test the fuel pump for 12V with the fuel pump in the circuit. The positive lead is exposed on the back of the fuel pump connector making it easy to test whether there is power to the pump with the pump connected. Just looking for 12V at the disconnected harness may result in replacing a good fuel pump like I did.

But now you have a REALLY good fuel pump, and you don't have to worry about it for another 15 years.

Did you bolt the main relay back in place, or did you shove it back in the wires? And if it was originally bolted in, did you get the mounting bolt out with a socket through the change drawer opening, or from over to the right. Did you drop the fuse panel?

[AZmike]

I left the bracket off the relay after I resoldered it a few years ago. To get it out that time I think I worked primarily through the change drawer opening. I know I didn't mess with the fuze block.

[Oldblueaccord]

good its up and running again.

I dont think the wiggy would help anyway thinking about it I dont think it works on DC or low voltage DC at least anyway. Swaping a good known part is the correct thing to do.

The how's and whys always get me even after I fix something like that. I guess thats whats keeps me in the troubleshooting business.


wp