I installed 42 lb injectors and a Walbro in tank fuel pump in my SS. Ever since then I have had a hard to start issue. It will not fire up at the touch of the key like it did before. It waill start on the second try though.

I put a fuel pressure gauge on the fuel rail and the pressure goes to 55 then drops back down. I have replaced the fuel pressure regulator and o-rings as and the problem is still there. I also put the stock injectors back in just to test fuel pressure and it did the same thing. Fuel pressure stay constant when running.

I'm thinking the fuel pump, but not sure. Anyone else experienced this?

Vince

 

your fuel presure will be go up when the key first comes on. then the pump shuts off and the presure drops some. when you fire it up the pump will come back on and it will go back up a little. that all sounds normal to me. you can actualy hear the pump turn on and off if you listen closely.

are you saying it wont fire at all or it just takes an extra revolution or so? an extra revolution probably isn't unusual. there are things to program like injector offset that might help but no one is sure what numbers to put in there for all the diferent injectors. you did reprogram for the size change didn't ya?

 

Yes, it was reprogramed for the larger injectors. I had a fuel pressure gauge hooked up to the fuel rail and the key was on but not started, the pressure shot up to 55, then when the pump stops running the pressure falls all the way back to 5-10 lbs.

In order to get it to start the first try I have to time it when fuel pressure it at the max pressure. But, it always starts the second try.

 

Since it does the same thing with stock injectors and new regulator, that rules out leaky injector or bad regulator.
My next guess would be leak-back through the pump. You could call Walbro or your supplier and ask about this. Maybe they'll trade you another pump to swap in.
good luck

 

Doesnt your truck have a returnless fuel system?

 

the leak back thru the pump sounds like a posiability. my presure only drops back about 5-10psi when the pump shuts off.

 

I bet the line on the pump is not tight and leaking pressure back thru. The pressure should stay up (45-50psi) for a couple of minutes after the pump is off.

 

The "returnless" systems with the return in the back by the tank started in 2004 for the trucks, before that the returns are at the engine.

 

yeah, thats another good idea. it sure sounds like a problem with or at the pump. you all ready did the regulator so thats all that is left. in all of my pumps the presure stays up for a long time, like an hour or more.

 

The pressure should not drop off like that. Llike Parish said, it should stay up there and only drop about 5 psi when the pump shuts off and then hold steady until the key is turned again. Some slight bleedoff, like maybe 1 or 2 psi in a matter of an hour will be ok.