So i have been vigorously trying to find out why my jeep has problems starting after a while of sitting. It would take 30 seconds to a minute of constant cranking to get it started. I replaced both positive and negative lines to the battery, and checked all electrical. Everything is good. I finally figured it out though. I am not getting any fuel pressure. I checked it today and after sitting for more than an hour or so the fuel pressure is completely gone and the pump doesn't turn on when i first turn the key on. I don't know why it is doing this and i don't know what to do to fix it. My dad and i completely rebuilt the fuel pump awhile back. In order for the fuel lines to start building pressure i must crank the key over. I need help fast because this is the one thing hold back buyers on my jeep. Thanks again

 

you rebuilt the pump? Maybe a new one would be in order. No pressure is due to a leak somewhere - either external or back through the fuel system, maybe the pump is letting the pressure backflow after sitting.

 

Okay, yeah we couldn't afford to buy a brand new pump assembly so we just rebuilt it all

 

I wasn't judging - just saying that would be a probable cause.

 

Yeah I know, just explaining a bit better about it. I will check that out

 

Check for leaks.

tjwalker has given great info on issues like this.

 

You either have an injector which is leaking fuel into a cylinder, a leak in the fuel line, a bad pump/check valve, or a combination of those things.

The check valve is a common problem. It prevents fuel from leaking back into the tank. It's a part of the fuel pump, so the pump would need to be replaced. Some people have been known to put in an inline BMW checkvalve very close to the pump, but the consensus is that this trick is a gamble. The OEM valve is regulated and should alleviate extra pressure. The inline valve will hold tight, so when you come home on a cool night with a pressurized line, beware of hot mornings. Some people have had issues with their fuel lines because of this added pressure due to heat.

You can test for the leak by pressurizing the system, screwing on a pressure gage and pinching the line. If the pressure holds, your injectors are fine, and the problem is in the line or pump.

 

Not your problem any more... You sold it