Fuel system woes - ZR-1 Net Registry Forums

Starman · 06-03-2022

Basically have driven the 91 twice this year to Costco. First time was for new Michelin PS2s and second time was to replace tire pressure sensor they broke. Car drove well both time and filled it up from about a quarter tank with fresh Shell premium and Vb Octanium octane boost. Both fuel pumps were replaced with Bosch maybe 10 years ago.

So after replacing the broken wheel stud from my friends at Costco, car will not start. Have a fast crank, good spark, no fuel pressure, no engine codes.

Did the wiring check at the tank, ohmed out fine. Did the pump test plug with both pumps hooked up and pulled 4.6A, but no pressure. Have not pulled fuses yet. FP1 fuse was OK. Car is in a lousy spot to get under dash.

Does anyone have the wiring diagram for the connector at the tank?

Open to ideas, I do have a FSM, but a bit cryptic at times.

Thanks

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Z51JEFF · 06-03-2022

The problem is that cars pissed off at you for taking it to some hacks.

Starman · 06-04-2022

Quote:

Originally Posted by Z51JEFF

The problem is that cars pissed off at you for taking it to some hacks.

Very true

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1991 Corvette ZR-1 · 06-04-2022

The relay may be toast. I believe it is over on the passenger side right below the glove box area. Guess it could not hurt to pull it and test. I don?t recall if a failed TPS will stop the injectors from firing. If you put the gas pedal to the floor and crank, the ECM recognizes a flood condition and will not pulse injectors. Not sure if a bad TPS would trigger the same reaction from the ECM.

XfireZ51 · 06-04-2022

Quote:

Originally Posted by Z51JEFF

The problem is that cars pissed off at you for taking it to some hacks.

They are very temperamental and demand attention.

mlipmd · 06-04-2022

If the pumps are both running but you have no fuel pressure, you could have a problem like I found with mine, but you have to pull out your pumps to inspect them.
My car was having a problem making it crank a longer time to start. stumbled a little on acceleration, had a little low fuel pressure. When I pulled out the pumps I found that one of the original plastic hose clamps was loose, the hose was able to slide up and down, and fuel was obviously leaking back into the tank instead of being pumped out to the fuel rail. I changed all those black plastic clamps to SS screw clamps, stopped the leak, and all is well since. So check your pumps and make sure all the hose connections are tight and that one didn't come off somehow or have a leak in it. It could be something simple like that.

Young1 · 06-05-2022

At 4.6 amps only one pump is running. Two pumps running is 7-9 amps. Verify primary fuse is good. Test again with primary pump fuse pulled from main panel. This will prove that your secondary pump only is running.

mlipmd · 06-06-2022

If the pump is pulling 4.6A it is running and car should still start, but if you have no pressure, something is wrong as you will have to pull the pumps to see why. A fuse or relay will have nothing to do with no pressure if the pump is running.

Starman · 06-11-2022

Quote:

Originally Posted by mlipmd

If the pump is pulling 4.6A it is running and car should still start, but if you have no pressure, something is wrong as you will have to pull the pumps to see why. A fuse or relay will have nothing to do with no pressure if the pump is running.

Agree, thanks to all for the feedback, hope to do some more testing today and will let everyone know what I find.

Do the 91s have a fuel cut off switch? And if so, where is it?

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mlipmd · 06-11-2022

Isn't that called a fuse? Located in the panel by the PS door. Lower right, 10 amp.

06-03-2022	#1
Starman Join Date: Sep 2008 Location: Speedway, IN Posts: 135	Fuel system woes Basically have driven the 91 twice this year to Costco. First time was for new Michelin PS2s and second time was to replace tire pressure sensor they broke. Car drove well both time and filled it up from about a quarter tank with fresh Shell premium and Vb Octanium octane boost. Both fuel pumps were replaced with Bosch maybe 10 years ago. So after replacing the broken wheel stud from my friends at Costco, car will not start. Have a fast crank, good spark, no fuel pressure, no engine codes. Did the wiring check at the tank, ohmed out fine. Did the pump test plug with both pumps hooked up and pulled 4.6A, but no pressure. Have not pulled fuses yet. FP1 fuse was OK. Car is in a lousy spot to get under dash. Does anyone have the wiring diagram for the connector at the tank? Open to ideas, I do have a FSM, but a bit cryptic at times. Thanks Sent from my iPhone using ZR-1 Net Registry

06-03-2022	#2
Z51JEFF Join Date: Dec 2007 Location: Fremont, CA Posts: 3,087	Re: Fuel system woes The problem is that cars pissed off at you for taking it to some hacks.

06-04-2022	#4
1991 Corvette ZR-1 Join Date: Sep 2018 Location: Florida Posts: 305	Re: Fuel system woes The relay may be toast. I believe it is over on the passenger side right below the glove box area. Guess it could not hurt to pull it and test. I don?t recall if a failed TPS will stop the injectors from firing. If you put the gas pedal to the floor and crank, the ECM recognizes a flood condition and will not pulse injectors. Not sure if a bad TPS would trigger the same reaction from the ECM.

06-04-2022	#6
mlipmd Join Date: Mar 2021 Location: Crawfordville, FL Posts: 220	Re: Fuel system woes If the pumps are both running but you have no fuel pressure, you could have a problem like I found with mine, but you have to pull out your pumps to inspect them. My car was having a problem making it crank a longer time to start. stumbled a little on acceleration, had a little low fuel pressure. When I pulled out the pumps I found that one of the original plastic hose clamps was loose, the hose was able to slide up and down, and fuel was obviously leaking back into the tank instead of being pumped out to the fuel rail. I changed all those black plastic clamps to SS screw clamps, stopped the leak, and all is well since. So check your pumps and make sure all the hose connections are tight and that one didn't come off somehow or have a leak in it. It could be something simple like that. Last edited by mlipmd; 06-04-2022 at 11:51 AM.

06-05-2022	#7
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 897	Re: Fuel system woes At 4.6 amps only one pump is running. Two pumps running is 7-9 amps. Verify primary fuse is good. Test again with primary pump fuse pulled from main panel. This will prove that your secondary pump only is running. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

06-06-2022	#8
mlipmd Join Date: Mar 2021 Location: Crawfordville, FL Posts: 220	Re: Fuel system woes If the pump is pulling 4.6A it is running and car should still start, but if you have no pressure, something is wrong as you will have to pull the pumps to see why. A fuse or relay will have nothing to do with no pressure if the pump is running.

06-11-2022	#10
mlipmd Join Date: Mar 2021 Location: Crawfordville, FL Posts: 220	Re: Fuel system woes Isn't that called a fuse? Located in the panel by the PS door. Lower right, 10 amp.