fuel pump works but wont hold fuel pressure

je3per-xj · 09-11-2008, 10:12 PM

ok im gonna try to make a long story short. not to long ago I did a 4.7L build and when I first fired it up It started running hot ( my hedder was glowing bright red) so I start troubleshooting. well I installed an electric fuel pressure gauge and found out that i was only getting 10psi at the fuel rail. I replaced my fuel pump and it started running great. then I noticed that I had coolant in my oil.

so I pulled the head off and got it inspected for cracks and warpage. it was fine. Im thinking (wishing) that the head gasket blew. so ive got it all back together now and I went to purge my fuel rail. and I cant get it to hold any pressure. every time that I turn the key I hear my fuel pump cut on and my pressure gauge will go up to about 2 or 4psi and then quickly falls back down to 0 psi. when I let off the key from trying to crank it I see the gauge go up to about 10psi or so then it quickly drops back down to 0 psi. any thoughts on the subject?

Dmax5er · 09-11-2008, 11:57 PM

Quote:

Originally Posted by je3per-xj

ok im gonna try to make a long story short. not to long ago I did a 4.7L build and when I first fired it up It started running hot ( my hedder was glowing bright red) so I start troubleshooting. well I installed an electric fuel pressure gauge and found out that i was only getting 10psi at the fuel rail. I replaced my fuel pump and it started running great. then I noticed that I had coolant in my oil.

so I pulled the head off and got it inspected for cracks and warpage. it was fine. Im thinking (wishing) that the head gasket blew. so ive got it all back together now and I went to purge my fuel rail. and I cant get it to hold any pressure. every time that I turn the key I hear my fuel pump cut on and my pressure gauge will go up to about 2 or 4psi and then quickly falls back down to 0 psi. when I let off the key from trying to crank it I see the gauge go up to about 10psi or so then it quickly drops back down to 0 psi. any thoughts on the subject?

Buddies truck done the same thing today and his fuel pressure regulator was bad. assuming your fuel injected... IF not, either your pump is going bad or the gas is going right thru the carb into the motor. pull your dipstick and smell it to check for that.

je3per-xj · 09-15-2008, 11:12 AM

the inner O-ring was cut on the fuel pressure regulator. got a new one and it works perfect.

09-15-2008, 11:12 AM	#3
je3per-xj Registered User Join Date: Feb 2007 Location: Mississippi Posts: 180 Profile Gallery Classifieds My Jeeps	the inner O-ring was cut on the fuel pressure regulator. got a new one and it works perfect. __________________ green 95 xj sport 3.5 R.E. lift S.Y.E., CV driveshaft, 4-degree shims Currie H.D. steering system black crager soft 8 wheels 31/10.5 a/t tires coming soon 5 in. lift, 33s, and the 4.7L STROKER that ive been building for the past 6 months