94 Accord with *almost* classic main relay symptoms, but doesn't seem to be the relay - Drive Accord Honda Forums | radio-pro.ru
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post #1 of 7 Old 02-09-2008, 01:04 PM Thread Starter
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Question 94 Accord with *almost* classic main relay symptoms, but doesn't seem to be the relay

I'm about to lose it. My symptom starts out looking like the classic key-at-II-no-fuel-pressure-MIL-Stays-ON. But with this 94 5sp EX, smacking/resoldering/replacing the relay doesn't help. Plus the car has to be at ambient and "cold", but ambient has to be above about 60 degrees to have this problem. Never a problem when driving, no problem restarting from a warmed up state, no problem if hot-soaked. Only when she's cold.

Leaving the key in the II position will after 2-4 minutes always get the fuel pump going, the MIL off and off I go. If the car is middling-warm it may only take 5-10 seconds before the pump gets going and I'm off.

I've verified there's no 12v back at the fuel pump when this happens but for good reason. I see battery voltage at the relay pins 6 (good) and 1 (bad) and the corresponding connections back at the ECM A25&B1 and A7, where they're good and bad (both 12v) in the no-start state too. I've jumpered the service connector and see no codes, MIL stays on all the time. I've got good grounds at the ECM A connector and the PGM-FI (MFR) relay.

For some reason the ECM isn't pulling its A7 (the relay's pin 1) down so the fuel pump relay can't start.

I don't know where to go now. Halp!!


Last edited by howard941; 02-09-2008 at 04:18 PM. Reason: mention MFR in body, replace angry with questioning smiley
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post #2 of 7 Old 02-09-2008, 06:09 PM
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Do you have a shop manual for your Accord? If not, go to and they have a fuel and emissions pdf that will help pinpoint the problem.

The MIL staying on is a clue to the problem. If you look at page 11-27, there is a flowchart for having the MIL on and not producing any codes. If you go through the diagnostics, you start by checking the fuses. You want to make sure that the fuse is making a good contact in the fuse box. Maybe bend the fuse tabs to make sure the fuse is secure. Go through that procedure and let us know what you find.


95 Accord EX MT
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post #3 of 7 Old 02-10-2008, 06:47 AM Thread Starter
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I guess I was getting way too ahead of where I needed to start. snippedout a lot of crap here related to my having the paper clip in the wrong side of the service connector

With the service connector in the MIL stays on all the time, I think indicating no codes?

I seem to need to be on page 27 of the pdf you linked (thank you)

It should warm up by this afternoon enough to see whether I can reproduce this other than by pulling the ECM and fuel pump fuses, which is the only way I can do it when its in the low 60s as now. What I'm seeing right now after I bent the fuses slightly is maybe a .25 second delay between turning the key to run (II) and the fuel pump kicking in for its two second run and all is good in the world. That doesn't give me a lot of time to run things down but when it gets into the 70s later it should fail for a lot longer - maybe 4-5 minutes if it gets up around 80.

Last edited by howard941; 02-10-2008 at 11:11 AM. Reason: remove contradictory stuff related to having the paper clip in the wrong side of the service connector and not being in code reading mode
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post #4 of 7 Old 02-23-2008, 01:12 PM Thread Starter
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Oh where oh where is a reasonably priced ECM

Quote:
Originally Posted by PennHonda View Post
Do you have a shop manual for your Accord? If not, go to and they have a fuel and emissions pdf that will help pinpoint the problem.

The MIL staying on is a clue to the problem. If you look at page 11-27, there is a flowchart for having the MIL on and not producing any codes. If you go through the diagnostics, you start by checking the fuses. You want to make sure that the fuse is making a good contact in the fuse box. Maybe bend the fuse tabs to make sure the fuse is secure. Go through that procedure and let us know what you find.
Good advice. The weather warmed up today and it started failing, perfect day to walk the flowchart. I wound up all the way at the bottom of 11-29 "substitute good known ECM". Just to confirm it I tossed the ECM in the fridge for half an hour, plugged it in, and it's fine (when it's below 60 degrees it always was OK). I assume it's going to start acting up once it warms up again and if it does that'd seem to confirm it?

Any thoughts on where to locate an ECM part # 37820-P0A-A01 that doesn't cost an arm and a leg? No joy with local junkyards
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post #5 of 7 Old 02-23-2008, 02:50 PM
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try car-part.com

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2002 Accord EXVL Auto Sedan - Nighthawk Black Pearl / Quartz, fog lights, mud guards, wheel locks, trunk tray
1994 Pontiac Grand Am GT Auto Coupe
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post #6 of 7 Old 02-24-2008, 07:47 AM Thread Starter
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Quote:
Originally Posted by benjamming View Post
try car-part.com
Found a bunch there - thanks.

This problem feels like a power-on-reset. Anyone know which parts on the ECM are involved in it? Some of the cheesier reset circuits I've seen in other places use a schmitt trigger off of an RC circuit and with all of the threads about the crappy electrolytic caps in these ECMs it might be fun to replace the relevant cap with something newer and see if I can revive this thing short of replacing it
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post #7 of 7 Old 03-02-2008, 09:24 AM Thread Starter
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Thumbs up Resolved

Swapping out the ECU with the exact replacement from a junkyard fixed it. I'm told ECU failures are really rare.

Thank you all for your guidance.
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