Fuel pump??

[markopolo]

So I have a 94 3.0 5speed that I just picked up. The guy I got it from said the fuel pump was bad. Instead of just throwing a fuel pump at it I decided to do my own diagnostics on it. When I got it home I had to charge the battery to get it to crank. It wouldn't start. I put a fuel filter on it and I got it to start. It runs rough has no throttle response and sounds like its working too hard to keep 4000-4500rpm. No vacuum leaks or fuel leaks. I have seen on the tech page fuel pressure should be between 30-40psi. I have checked fuel pressure and after 4 key cycles tops out at 25psi. Compression looks good too. I just want to make sure that I am on the right track in sayin that the fuel pump is bad.

 

[martin]

Before assuming the pump is bad I would check that the fuel pressure regulator is working correctly.

 

[markopolo]

I have pinched off the return line and yielded the same result. I have also pulled the vacuum line off the regulator while it was running and there wasn't a change in the way it ran nor was there any gas coming out of the vacuum port.

 

[Rearanger]

I have pinched off the return line and yielded the same result.

The FPR is a normally closed valve that bleeds off excess fuel flow to the return line when pressure exceeds the setting. If you pinched off the return line from the regulator then there is no place for excess fuel (pressure) to go, in effect you are stopping the regulator from working as designed. Pressure should rise.

Question is, is the pump pressure/flow too low that it is not producing excess flow to be regulated by the regulator, or is the regulator bad, not fully closing?