# Fuel Pump Relay Noise?



## TheTygur (Jul 26, 2009)

Well, first off, 85 Z31 NA 5spd
Replaced all parts tripping computer codes. (and a couple more)
All new plugs/wires/module/cap/rotor.
All new fuel filter/pump/relay/FPR.
Timing is on. MAF is good.

Problem: Randomly, usually when going up a hill but not always, the fuel pump relay starts buzzing and clicking. Soon after you feel a fuel cut and the engine loses most power or dies for about 5 seconds. Usually this happens when in gear and the engine comes back to life while coasting. It has happened when idling though. Its pretty unsafe, as the car will randomly buck or shut off in traffic. Apart from this problem, the whole system runs great. Gonna check the wiring for shorts and try and check the engine computer which I have read controls the relay's ground. 

The computer by the way, has been replaced with a junkyard one by previous owner. I don't know when or even if its the correct one, he pretty much cut and replaced the entire harness to the computer as well and did some sketchy wiring in the engine bay which I have since fixed.

Think its probably the computer? What could agitate it while its going uphill? Its got plenty of power normally.


----------



## TheTygur (Jul 26, 2009)

UPDATE:

I ran a switch to basically manually activate the fuel pump relay, or, more accurately, bypass it. You can instantly tell a difference right from when it starts up. It will run a bit choppy, then when I flip the switch it evens out and runs well. Turn it off again and it goes choppy again. I'm gonna have to eventually trace down the wiring and test the computer but I need it as a daily driver so this fits the temporary bill.

The other question this brings up is: the 4 lines out of the relay. The activation lines for the relay look normal but on the lines that the relay connects when activated, one looks spliced. Not so much spliced as it has an insulation coating on it with braided wire inside the coating not connected to the central wire. Kind of like a coax tv cable. Is this the way they came or did previous owner do some strange splicing here too? I noticed a lot of the bolts and such are missing from the panel that covers the relay... hmmm...


----------



## Faja (Aug 31, 2009)

If you trace that braided wire, where does it lead to - is it going to the battery?


----------



## TheTygur (Jul 26, 2009)

Its almost certainly either grounded somewhere, or the ground coming from the fuel pump. That wire that the relay controls is the fuel pump ground. But I don't have the time to tear the panels out and trace it, I have to drive it daily, plus its friggin cold and I don't have a garage either.


----------



## Faja (Aug 31, 2009)

Yeah, it sounds like you definitely have some wiring problems specifically to your fuel pump so I would check out all the connections from the pump itself all the way back to the battery and see if you can find the short or loose connection somewhere along that line.


----------



## TheTygur (Jul 26, 2009)

Yeah, hopefully this oddly installed engine computer hasn't given out. The problem has gotta be in the control wires to the relay from the ECU since bypassing the relay's control makes everything work fine. Oh well, I'm gonna restune it in spring/summer anyway. At the very least, stripping and refinishing the interior and revamping the suspension, and body/paint work.

At least for now, with the bypass switch, its an absolute pleasure to drive compared with my last few cars. Its still a bit difficult as the front shocks are basically nonexistent haha.


----------

