Loosing fuel pressure

[87hottness]

Ok i need some advice recently i noticed that on first key on when my fuel pump primes the system engine not running my fuel pressure drops fast to 20 and holds there but with engine running it holds like normal i don't smell gas any where around the car like its leaking just cant figure out where the problem is i was thinking the regulator because i have random high blms making me think its leaking vaccume does this make sense?

 

[SHADOWII]

You can use a pair of vise grips to pinch off the fuel return, be sure not to crush the hose. Pressure should hold if the regulator is the problem. If it drops, check for a leaking injector by pulling the plugs and checking for fuel. If you find fuel on the plugs, it can wash down the cylinder walls! If no problem found there, it is probably the f/p bypass/pressure relief not holding.

 

[87hottness]

Ok thanks where is the return line located and where is the f/p bypass pressure relief located

 

[87hottness]

Also wouldn't i be able to feel it while driving if it was an injector?

 

[87hottness]

Anyone have any input?

 

[Nick Micale]

I am dropping the fuel tank in the AM on a car with the same issue you have, and plan to replace the pump.

It is not a recent pump in a stock car, and figure 99% it is a bad pump!

 

[87hottness]

I don't think its the pump they normally go competely my car still runs fine

 

[Nick Micale]

Maybe after changing a few hundred pumps you may "think" differently?

Could be a voltage issue or a bad coupler hose in the tank, but no one can state what exactly the problem is until it is found and fixed.

 

[blackazz]

Had the same problem, then the pump goes weak . replaced my pump now it holds after key off.

 

[87hottness]

And you never had problems driving the car? My car runs fine

 

[Nick Micale]

The car I just finished installing a new fuel pump was running "fine" also, it was driven across town to here. But now it has 40 psi fuel pressure at idle instead of 25 psi.

Hope your issue works out well for you!

 

[87hottness]

My car has 40 psi at idle its when i shut the car off it drops to 20 instantly

 

[blackazz]

That's the sign of a weak pump.are you sure it rises 1 lbs of fuel pressure with 1 lbs of boost.my car ran great ,just as soon as I went to get on it pump was only giving half at full throttle.

 

[87hottness]

I don't know haven't gone full throttle because i don't want to was out a cylinder if it an injector also i tried adjusting my regulator and the pressure doesn't move at all up or down that is odd to me

 

[blackazz]

Reread post #2