kennebellgt

I changed my fuel pressure regulator and the problem is still here and i pinched the fuel return line and the fuel pressure spikes up, what does that tell me? Thanks.

AdderMk2

if your fuel pressure falls off immidately when you shut the car off, it means you have a leak inside your tank. either the rubber hose that runs from the pump to the sending unit is bad.. OR the 1 way check valve in the pump crapped out on you


im surprised nobody else knows this

FivePointOhh

^^^this is is what i had him check for by pinching off the return line. exactly how i pin pointed my bad check valve in the pump.

replaced the pump, issue solved

AdderMk2

Actually, thats wrong. pinching the return line will only indicate a bad FPR. the fact that he instantly looses pressure shows that there is a leak in the fuel system. anything after the regulator is irrelevant. his leak would be before the fpr, and since it is not physically leaking on the ground, it means the pressure loss is contained.

a bad check valve in a pump will not cause a loss in pressure. only the systems inability to hold pressure when powered down.

the fact that you have almost no pressure, and the pressure drops to zero... TELLS me that your fuel pump to sending unit hose is shot.

FivePointOhh

^^thanks keith! well i got a lucky guess with mine then. i learned somethin new today.

Liquid_02

As adder said it is a FP, I've to this day, never seen a hose blow off inside the tank itself, I can imagine it's possible, if someone installed it and forgot to clamp the hose, but 99% sure you need a FP. That's generally the start of the failure of the fuel pump, long cranking times due to the check valve not working. Also, since you state it drops off when you give it throttle, that means you have no volume, so it can't possibly be a hose, or regulator. If it were a hose, it would not matter how it's running, it would always leak off, since it only drops when you give it throttle, engine demands more fuel, fuel pump can't keep up, so the pressure drops.

Think of it this way. If it were a hose, fuel is always leaking back down to the tank, you step on it, pressure drops, therefore your leaking hose should no longer leak, as there is no pressure to force it through the hose to cause it to leak so it should start building up pressure again. Fuel pump always flows the same amount of fuel on older model cars, so at idle it's still flowing the same amount of fuel as it would at WOT, therefore, if you have 40psi at idle, it's still flowing the say 155lph, you step on it, it doesn't change anything, still flowing it's 155lph.

If it were fuel pump, it's pressurizing the little bit that it can, regulator makes sure of that, you could have a 5gph fuel pump in your car and it will still have fuel pressure at idle, regulator just closes up, about 99% of fuel is returned to tank at idle on a properly functioning fuel-system. Once you step on it, since it doesn't have the volume, regulator closes even more, but pump can't keep up and falls on its face.

So in summary, you need a pump.

kennebellgt

Thanks All you guys, it was the fuel pump, i took it off and was able to fairly easy blow air through the feed line, i took the fuel pump off the hose and pushed air directly in the inlet hole on the fuel pump and could blow air right through the pump. Anyways i just want to Thank you guys, I really appreciate the help.