What wire do I need to check at the pump and what should the voltage be at the pump? What about cold start verses starting when its warm. The only time I get the low pressure reading is when its cold. After I get it started and warmed up the fuel pressure goes back up to 60 psi and it will start just fine. I just had the battery and alternator check and everything checked out OK ,and my mechanic buddies were at a loss for what the problem could be. Only thing they could think of was the pump.

 

I've posted wiring diagrams and connector views in the past. A search or two should turn them up.

 

I appreciate all the help I'm getting. But after searching I can't find anything about checking what the voltage at the pump should be. the wire colors I have are blk/wht, gry, ppl, and blk. From searching around I'm thinking I need to check the voltage at the gry wire or ppl wire, and I don't know what the voltage should be. This will be the last thing I'm checking before I pull the tank and swap out the pump.

This problem seems to have everyone that I talk to baffled. I get good pressure when the engine is warm and not after it sits for a few hours. but starts fine when I jump it.

 

did you have to replace the harness when you put in the the pump

 

Just ran that search again and this is what popped up! Just have to learn the quirks of the search feature.

 

Thank you. When I did the search I pulled up all kinds of pages with tons of info that didn't pertain to my problem. There was so much it was kind of overwhelming. Thanks for the link and the quick lesson on how to use the search feature.

 

Well here's what I found so far. I pulled the relay and tested pins 30,85,and 86 for ground and voltage. Pin 30 has 12 volts, 86 is getting to a good ground, and when I turn the key on I get 11.4 volts on pin 85. When I hook up to jumper cables the voltage at pin 85 jumps up to 13 volts. I get the same thing at the pump when the key is turned on I get 11.4-11.5 volts checking the gray wire.

 

Well.............. Any ideas?


Is the 11.5 volts normal when my battery reads 12.5 volts? Should the pump still work at 11.5 volts or is it junk? If the one volt drop isn't normal where should I stat looking now? VCM? Is this a simple part to swap out? Or could the problem be in the ignition switch it's self.

Sorry for all the questions guys, but I don't have a service manual for this vehicle yet, and money is tight right now. I just got back to work after being laid off for six months, and who knows how long this job will last. (Oh the joys of working construction.) So running to a garage and paying someone to fix this is out of the question for now. Not to mention my wife needs a car to get to work and the kids to the babysitter and school.

 

I was hoping to get an answer before dropping the tank and replacing the fuel pump again. But that didn't happen, I swapped out the fuel pump with another one and everything is working fine now.

Anyways, thanks for the help guys. I'll try and return the favor when the time presents its self. I'm always willing to help when I can.

 

BTW swartlkk, Love the red and white full size in your sig picture. I had a 78 when I was in high school. I loved that blazer, someday I'll find me another one.