Ok, got a FP gauge on the car today. The car had sat for about 2 days without running, and when it sits I always seem to have a problem with it starting. So I hook up the gauge and turn the key to the on position, not running. Fuel pressure only reads 28PSI!! Start the car up and at idle it hoovers around 38-40ish. Turn the car off and turn the key back to the on position without it running and it goes to about 42-44 and stays there. So obviously this leads me to believe that something is wrong when it sits, it won't build up enough pressure. Any ideas?

Thanks in advance guys.

 

how long does it take to lose pressure and go to 0... if it takes a while im gonna bet that you have a leaky injector or a very slow leak in the regulator, if it's fast then its a bad check valve in the pump but heres ways to check..

theres 4 things that can caused that, first your not keeping fuel pressure when the car is off, i have the same problem with my z im not going to worry about it until my rebuild though but the problems could be this

bad regulator - pull vacuum line off of regulator and see if gas comes out of it with the car running, or pinch off the fuel return line prime the pump and if the pressure stays you have a bad regulator

leaky injector - pull fuel rail and injectors out of manifold enough so you can see the tips of them prime the fuel pump and watch to see if any of them leak while the pressure is droping..

bad fuel pump check valve - the easiest way to diagnose is to check all of the other problems that i listed and verify that they past there test then thats all there is left to replace is the pump

gas leak in the lines somewhere - common sense if it's leaking out other then in the motor then theres your problem...

hope that helps

 

Definitly helps man, thanks. It's losing pressure slowly, I had the gauge hooked up for about an hour or so with the key off just sitting and it lost maybe 2 PSI to around 38.

 

yep im gonna bet you have a leaky injector...

 

After it sits for a couple of days, try cycling power KOEO for 2 seconds and off. Try this 3 or 4 times and then start the car. If it starts quickly, you know you have a drain back issue. If it doesn't start quickly then the next time you try to start it after sitting for a couple of days, press the throttle to the floor and crank it. If it starts quickly then, you know you have a leaky injector.

 

Thanks for the ideas man, I'll give them a shot. When it does sit for a couple days, after it gets started it will run rough for about 20 seconds, thats what leads me to believe it's an injector, its dumping fuel and runs ****ty until it burns it off. I'll keep troubleshooting and see what I can come up with.