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> Fuel Pump wont run off relay board...
D1A3
post Jul 17 2010, 06:30 PM
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Car died a few weeks ago while driving it and I think I know what is causing it...

Turns out, my fuel pump was not getting power. I temporarily rigged up the pump to run off my driving light relay and the car runs great. I traced the harness power wire (black/red stripe) back all the way to the relay board and could not find any break/melting or anything suspect.

I found in the Haynes Manual that the fuel pump relay should have voltage at 86 and ground at 85. Guess what? I checked and have voltage at 86, but NO ground at 85. The manual says in this case to check the "main relay." What the heck is that? It references the "fuel pump relay" in other places uniquely, so wondering what a "main relay" is on our cars.

Also, mentions that there could be an open circuit causing the ground to fail. What should I check?

The relay being used is known to be good, so any ideas or am I looking at replacing the relay board?

Thanks everyone!
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904svo
post Jul 17 2010, 06:36 PM
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Jason, that ground on pin85 comes from the ecu harness pin#1. Check your grounds at the back of the engine case on the xmas tree grounding point.
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D1A3
post Jul 17 2010, 07:53 PM
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Thanks Larry. Going to check that now.

BTW: I'll be at the Concours tomorrow at Hennessy. If you are around, stop by!
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D1A3
post Jul 17 2010, 09:26 PM
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Larry,

Checked the grounds that are just on the passenger side of the air intake and they all are grounded well. Is there another spot Pin85 could get it's ground from? I'm really at a loss here...
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Cap'n Krusty
post Jul 17 2010, 10:53 PM
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Two words of advice: "wiring diagram". Available on the Pelican website. The computer supplies the ground. The main power relay is the one forward of the fuel pump relay. From the back: heater fan, fuel pump, main power for the FI system, heated rear window.

The Cap'n
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swl
post Jul 18 2010, 07:21 AM
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disconnect the 4 pin connector and jump Pin III to ground. (you are doing what the ECU normally does) Key on. Does the pump run?

If yes then you may want to disconnect the harness from the ECU and inspect the condition of the contacts. Clean as necessary. Reseat the connector and try in normal mode (4 pin connect plugged back in). Remember that the pump will only run for a second or two at key on. Then it shuts down until you start cranking.

If no do you have power at pin 30 of the fuel pump relay?
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SLITS
post Jul 18 2010, 08:18 AM
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Check the main gorund bundle, near relay board on inner fender. Single stud with multiple ground wires. Fuel pump ground wire is one of the bundle.
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ahdoman
post Jul 18 2010, 04:25 PM
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Also, don't forget the two fuses on the board next to the relays. One of those is for the fuel pump. They get corroded so wiggle them and make sure the contacts are clean.
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blitZ
post Jul 19 2010, 07:41 AM
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Did you try swapping out the fuel pump relay on the relay board?
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D1A3
post Feb 20 2011, 05:44 PM
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OK, Just FINALLY completed a permanent fix for the Fuel pump issue!

To get me by, I had wired the fuel pump into my fog light switch. Worked fine, ran some good auto-crosses and perhaps had a great anti-theft/emergency fuel cutoff...

Tonight I am happy to report that the issue has been resolved. :-) After checking everything that was suggested and running some of my own tests to verify the continuity of the power wire to the fuel pump, I replaced the relay board. Special thanks goes to Al Meredith for his help to locate one for me. (IMG:style_emoticons/default/beerchug.gif)

I know everyone says the relay boards don't go bad, and the one coming out actually looked pretty good (visually speaking). But, good looks don't mean all is well underneath...

Thanks again for everyone's support and you will see me around Atlanta a lot more now that I don't have this to worry about any longer. (IMG:style_emoticons/default/driving.gif)
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markb
post Feb 20 2011, 06:11 PM
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Glad you figured it out. I had a relay board that worked fine most of the time, but on really hot summer days would quit when it got too hot. Replaced it & never had another problem. Of course any car of mine has "unusual" problems. (IMG:style_emoticons/default/biggrin.gif)
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