Pressure Regulator Or Fuel Pump?

denngril · September 2, 2008

I have a '98 5.7 with 165K on it..have replaced the fuel pump about 20K ago; am experiencing the classic "slow start" (engine off pressure 58-60). With a litttle on-off with the starter, it will catch and run fine. Starts fine when warm. My question is do I need another fuel pump? Or a regulator? (And where is it? How do I test it? Chilton is vague!)

Thanks!

Denny

abracadabra · September 5, 2008

I have a '98 5.7 with 165K on it..have replaced the fuel pump about 20K ago; am experiencing the classic "slow start" (engine off pressure 58-60). With a litttle on-off with the starter, it will catch and run fine. Starts fine when warm. My question is do I need another fuel pump? Or a regulator? (And where is it? How do I test it? Chilton is vague!)

Thanks!

Denny

Pretty sure 58-60 is low. Pretty sure it should be 64-65 for cold start. Block the return and check that pressure comes up to 75-85, don't run the pump like this for long just check for pressure.If you have full pressure with return blocked, but low unblocked it might the the pressure regulator leaking or not holding.

denngril · September 5, 2008

I have a '98 5.7 with 165K on it..have replaced the fuel pump about 20K ago; am experiencing the classic "slow start" (engine off pressure 58-60). With a litttle on-off with the starter, it will catch and run fine. Starts fine when warm. My question is do I need another fuel pump? Or a regulator? (And where is it? How do I test it? Chilton is vague!)

Thanks!

Denny

Pretty sure 58-60 is low. Pretty sure it should be 64-65 for cold start. Block the return and check that pressure comes up to 75-85, don't run the pump like this for long just check for pressure.If you have full pressure with return blocked, but low unblocked it might the the pressure regulator leaking or not holding.

Thanks for suggestion..I was thinking the pressure was just on the cusp of running the injectors. Another question: where does one block the return line? I see a metal line. (Pressure holds on the incoming line fine)