Typ89

I think I finally figured out what is wrong with my engine. Fuel pressure is very low, does anyone know what it supposed to be? and what could cause this? On the fuel rail theres a fuel pressure regulator, which I replaced thinking that this was the problem. When I took the fuel line that connects to the pressure regulator off barely any fuel came out and there was no sign of pressure. Fuel filter was replaced as well.

VAP

<center><img src="http://pictureposter.audiworld.com/711/customfuelrail2.jpg"></center><p>
However, the fuel line does not maintain or hold fuel pressure when engine is off. After 5 minutes it's down to about 30psi or so and 10 minutes later it's at "0" psi. Pressurized fuel is releived and goes back to the fuel tank and "leak-down" starts as soon as key is turned off. Fuel pump reprimes the fuel rail to 58psi when ignition is turned on. That takes about 2 seconds and is the "buzz" you hear when when ignition switch is turned on.

Only one way to really "know" fuel pressure and that's to either measure it at the fuel rail or mount a permanent gauge in the fuel rail.

Typ89

Car was running less than 10 mins before I removed the regulator, engine is missing sometimes and I have delayed throttle response and no power.

VAP

liquid fuel that spills out of the FPR when removing.

Typ89

Okay; but If I do have low fuel pressure what could be the reason why? Fuel pump?

VAP

basically anything/everything between the fuel tank and the injector pintle. But knowing these cars as I do I'd look at the electrical/ignition system before even considering fuel system.

Typ89

I dont think I have a fuel pressure gauge; is there any other way I can test fuel pump to see if it works properly? And where is it located? under the back seat in the gas tank? Thanks for your help

VAP

run between 80/90psi ALL the time. It's the FPR that reduces that pressure to 58psi at the fuel rail and injectors. The high pressure cut-off circuitry turns the fuel pump off at higher pressure then allows it to turn back on when pressure falls below 80/90psi. Our fuel pumps have no "rheostat" type circuitry whatsoever. They are "full-on/full-off" only.

When they fail they will sometimes give one or a couple of no-start condition warnings. Sometimes they just fail suddenly/abruptly with no warning whatsoever. Short of a fuel line restriction/blockage there's no way they can operate at a reduced pressure as they are "on/off" only with a high pressure shut-off provision. When line obstructions cause a reduced pressure it's always ahead of the blockage. That is to say the fuel pump is still pumping at 80-90psi behind the restriction.

When our fuel pumps fail the car doesn't show a slight or intermittant miss, reduced power or slow throttle response. It dies summarily, on-the-spot and goes nowhere under its own power until the pump is replaced.

JoeD_KC

Sorry I'm late to the conversation. VAP - would you suggest that a faulty FPR might be (or would never be) the cause of difficult starting? My engine runs great, but always requires excessive cranking to start-up. I was going to replace the FPR, injectors, &amp; plugs. Your thoughts, please?