No power to fuel pump, wiring help needed.

[nherbst454]

I just bought a 1990 ZR1 and am looking forward to get it running again. I purchased it from my widowed neighbor and the car has been sitting in storage for many years. I took the dash apart and found a massive mouse nest in the passenger side behind the dash. Most of the wires look to be in decent shape (a few have the insulation nibbled but I can fix that.)

I checked voltage to the fuel pumps and am getting nothing. I removed the fuel pumps and tested them by connecting the connectors directly to a battery and they are both dead (no humming).

I've removed the dash panel so I can access the relay connectors and am trying to figure out which relay is for the fuel pump and if I can jumper it when I get the new pumps installed. I will also take the relay out and test it but I probed the dark green / white wire which I believe is the pump 1 control signal from the ECM and I'm getting no signal to turn on the relay.

Any help would be appreciated!

New ZR-1 owner, Nate

[RussMcB]

Welcome, Nate. Glad to hear you are bringing a '90 ZR-1 back to life.

I'm afraid it's been too long since I've worked on my fuel pump to remember the details about that system. I think the FSM has troubleshooting steps to help you identify the problem(s). Marc Haibeck might be a good person to hook up with. He may even have something on his web site regarding the fuel system. It's worth your time to look at all of the technical information he has provided: http://www.zr1specialist.com

[Ccmano]

Here you go... from the 90 FSM Electrical Diagnosis Manual

[nherbst454]

Thanks for the diagram. I checked the relay and it seems to work when hooked to a battery. I also checked that the ground is functional which it is and I have continuity from the output pin on the relay all the way to the fuel pump connector so the wiring seems to be good. Even with the key on I believe that the control signal (verified continuity of the control wire from the wire to the ECM) is not being commanded on by the computer.

I tried to scan codes using the digital dash, all I'm getting right now is H41 when it first scans then nothing when it says 1.0 or 4.0 ( I just get dashes).

Any thoughts on what could be causing the computer to not turn on the fuel pump output?

I'm not sure if it's important but I've also noticed that the security light flashes when the door is open but goes away when I turn the key on. Not sure if this is normal or not.

Thanks for all your help, I'm looking forward to getting this beauty back on the road!

[nherbst454]

Any thoughts about the VATS causing no power to the fuel pump?

[nherbst454]

I've ordered a FSM and it should be here sometime next week, does anyone know if the logic diagram for the ECU is in this? I'm trying to determine if the ECU needs to see some other inputs before it will turn on the fuel pump output.

[S.hafsmo]

User WVZR-1 has electronic versions of both the FSM and the 8A electrical supplement you'd be able to aquire for a few $. These are also possible to do searches within.

[Ccmano]

Originally Posted by nherbst454

Any thoughts about the VATS causing no power to the fuel pump?

Highly likely. However I’m not versed troubleshooting that system. Do a search on the forum. I’m reasonably sure there are volumes written on the subject.

Did you buy new pumps yet?
H

[nherbst454]

Originally Posted by Ccmano

Highly likely. However I’m not versed troubleshooting that system. Do a search on the forum. I’m reasonably sure there are volumes written on the subject.

Did you buy new pumps yet?
H

I ordered a new complete pump setup with sending unit, it should arrive today.


After doing more research on the VATS system it looks like that would result in a no-crank condition but I can get mine to turn over, just won't supply power to the fuel pump relay.


Does anyone know if there is a fuel pump shutoff on this car? I'm wondering if it's possible that this is tripped, telling the computer to not energize the relay.


Finally, I would hate to go this route, but if all the wiring, relay, pumps are verified good but the output is not turning on from the ECU does anyone know how I can test the ECU itself to make sure it's functional?


Thanks for everyone's help!

[nherbst454]

Update: I found out my issue was that the fuel pump is only activated for ~2 seconds after key on and each time I checked it at the connector it took more that 2 seconds to get to the back of the car!

New fuel pumps installed and she fired up. It does seem to take a few more rotations to start than I’m used to with newer cars, any thoughts on that? I’m thinking a fuel filter (car only has 5000 miles on it) and possibly removing the injectors to clean them.