Fuel Pump Issue

[KFoster]

I know this has been discussed in several threads, but I wanted to outline my issue to see if it relates to one I read about a loose wire at the top of the tank or something else. I have used the threads to help. Car ran great a couple weeks ago, then last Friday it would not crank. It would fire after the initial start, then stop after a few seconds. Strange to me that the fuel pumps could work one day then not the next. This has not been an issue and there has been no recent work performed on the car. New battery a few months ago, but fine since and it has been driven many times since then. Car will start for about two to three seconds. Fuses are good and I swapped relays around after finally figuring out where they are. I checked fuses on the side of the dash and under the dash. Horn hasn't worked since I bought it, so swapped the interior light relay with the fuel pump relay with no change. Using the sticky thread, I checked the fuel pump with the underhood connector. It would show 6.5ohm for a split second, then .5 ohm. Repeated this several times. Pumps did not kick on, no pressure. Car turns over and will fire, but only run for a couple of seconds. Very repeatable. No pressure in the rails. I haven't put a gauge on it, but you can push the valve and some fuel runs out but no pressure behind it. The connector block behind the battery looks fine, wires feel tight on it. So, several threads out there have contributed to my investigation. I believe the fuses and relays to be good. Will fire, but not stay running. Anybody have this particular issue. I could see a loose wire causing it, but how does it sit for a week and a wire become loose with no intermittent trouble prior. I have not checked the wiring at the tank nor see if power is making it there. That will be next though. Any other thoughts. Could the pumps die overnight like that? I really thought it would be a sticking relay. My experience is they can stick on. I hate electrical issues. Any help is appreciated.

[KFoster]

If it helps. Car is a 90 ZR1 with 51k miles. SLP/K&N filter kit. Chip. Flowmaster exh.

[We Gone]

One of the posts had a procedure that Marc H. has on his site to check the pumps.

http://www.zr1specialist.com/HAT%20Web/articles/The%20ZR-1%20As%20Tanker%201.pdf

[Dynomite]

One of the posts had a procedure that Marc H. has on his site to check the pumps.

http://www.zr1specialist.com/HAT%20Web/articles/The%20ZR-1%20As%20Tanker%201.pdf

Now...that is interesting.......another use for the ZR-1 :D

[A26B]

Sounds like a primary fuel pump failure. Implement the ful pump test procedure that isolates each pump (primary & secondary) to check fuel pressure with key on, engine off.

[KFoster]

Pulled the wires at the pumps. Purple has power. Key on, gray and gray/green have power for several seconds. Maybe the pump or pumps are dead. Weird it would happen like it did. Guess I should be happy I didn't have to tow it.

[RussMcB]

We traced my problems (with similar symptoms as yours) to two plugs: One at the plug at the top of the plate (three prongs) and the other down onto one of the pumps. Sometimes there was a good connection and other times 12v didn't get to the pumps.

FYI - It's not too hard to take the pumps and sender out of the tank for easier bench testing. We used a battery charger to touch 12v to different places to pinpoint the breaks.

Good luck.

[KFoster]

Definitely worth a look. Thanks Russ. Getting the pumps out should be no problem, but should I go ahead and change them out since they may be original and it seems like this might be a weak area for this car? I appreciate everyone's input and I read the thread on where to buy the pumps. New gasket needed as well? I'll get one if they have it.

[KFoster]

Its fixed. Here is what I think it was. Most likely was. I never could hear the pumps run. Tank was at 3/4 full, and when I tested it after it was together by energizing them at the tank connector I could barely hear them. So, even though they weren't showing constant ohms while checking under the hood they could have been running while supplying no fuel. When I took the pumps out the top hose that connects to the metal pump housing was off. I thought maybe I knocked it off taking it out. Those factory plastic clamps were a dumb idea new and these looked old and original. Could slip the hose on and off without removing the clamps. They are crap and I replaced all the plastic ones with proper metal ones hose clamps. Tested each pump and it ran fine. Put them back in and as stated they tested fine. Cranked the car and it ran great. Fired right up with no issues. Must have just been the top hose had popped off. Hope this helps someone. Thanks for everyone's input.

[Dynomite]

Its fixed. Here is what I think it was. Most likely was. I never could hear the pumps run. Tank was at 3/4 full, and when I tested it after it was together by energizing them at the tank connector I could barely hear them. So, even though they weren't showing constant ohms while checking under the hood they could have been running while supplying no fuel. When I took the pumps out the top hose that connects to the metal pump housing was off. I thought maybe I knocked it off taking it out. Those factory plastic clamps were a dumb idea new and these looked old and original. Could slip the hose on and off without removing the clamps. They are crap and I replaced all the plastic ones with proper metal ones hose clamps. Tested each pump and it ran fine. Put them back in and as stated they tested fine. Cranked the car and it ran great. Fired right up with no issues. Must have just been the top hose had popped off. Hope this helps someone. Thanks for everyone's input.

Good information :thumbsup:

Thanks :handshak: