Need some fuel pump info.

[ilmk123]

I have a 96 GMC Yukon Suburban with fuel pump problems. I have some questions. The problem is electrical. I have 12 volts at the pump for only a few seconds. I know that it is suppose to pump up for a few seconds and then shut off. The problem is that the pump never comes on. We have checked the ground and re and re checked everything. Have replaced the pump. Hooked the old pump to battery and it runs. So Is there a pressure shut of for the pump? Is it just a check valve type of system and does not shut off the pump? Does the pump run all the time the burb is running? Thinking of just running a igntion on hot wire back to the pump. I know that it means the pump would still be running in case of accident. If any buddy has a schematic of fuel pump system that would be great! I hope somebody can answer my questions. Thanks in advance! Scott

 

[SunlitComet]

Have you tested for spark during cranking as well. If it did not spark either during cranking then I would suggest you have a fault in the crank sensor or pcm. Hook up a scanner and look for rpm when cranking to see if any rpm's show. As you mentioned the the pump will prime for two seconds at key on after being off for ten. That would indicate that the fuel control circuit is working from pcm to pump which would leave the input data such as a defective crank sensor circuit. During cranking and running the fuel pump relay is commanded on.

 

[ilmk123]

I do know that if i put some gas in the TB it will run for a few seconds......Any other thoughts?

 

[SunlitComet]

That would seem to indicate that the crank sensor is fine. So when you turn the key and start it normally on its own it puffs and sputters out or what? Have you actually had a fuel pressure tester on the whole time during testing?