fuel pump prime,

Aiello

Member
Jan 30, 2021
11
2
13
66
West Palm Beach Florida
Hi all, does anyone on here know if the following is normal for a 2001 mustang gt? What happens is on initial fuel pump prime, pressure goes to 32 Lbs.
after driving car and shutting it off then restarting, the pressure goes to 55 Lbs. then back to 32Lbs once running. Am I correct to assume there is residual pressure in the line and the prime cycle is adding to that? Totally confused. thanks
 
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COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
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Sea of Tranquility
I've never really checked mine at startup but sounds plausible the pressure would be up briefly. What are you measuring with?
 

Aiello

Member
Jan 30, 2021
11
2
13
66
West Palm Beach Florida
Thank you for answering, odd thing about this is it just started happening after I replaced the fuel pump. (with a factory one) also discovered on a cold start up,
it will go to 32PSI, if I shut it down and restart it still goes to 32 PSI only after it has warmed up after a short drive the pressure goes to 55PSI. Ghost in the machine!! Measuring with an Autometer gauge.
 

COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
7,508
948
223
Sea of Tranquility
Normal fuel pressure is 35-50. Did you notice what it was before you changed the pump? You might look at the fuel pressure regulator
 

Aiello

Member
Jan 30, 2021
11
2
13
66
West Palm Beach Florida
Normal fuel pressure is 35-50. Did you notice what it was before you changed the pump? You might look at the fuel pressure regulator
Thanks for the reply, the fuel pressure before I changed the pump would always prime to 32 PSI on cold and hot start. Only after new factory pump went in does it prime to 55 PSI. Also not throwing any codes. Would the fuel pressure regulator throw a code?
 

COramprat

...I can take it. I think.
Mod Dude
Mar 2, 2003
7,508
948
223
Sea of Tranquility
Thanks for the reply, the fuel pressure before I changed the pump would always prime to 32 PSI on cold and hot start. Only after new factory pump went in does it prime to 55 PSI. Also not throwing any codes. Would the fuel pressure regulator throw a code?
It should. P191 or 193. If it isn't I wouldn't worry too much about it unless you are having drivability issues.