checked my fuel pressure
05-22-2014, 10:27 AM
#1
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Year: 1997
Engine: 4.0
checked my fuel pressure
it reads 48 psi at idle. seems high. I have to poor man prime it which is what sparked the inquiry. it bleeds off to 8 psi within 5 minutes after shutting it off.
edit: 97 xj. 4.0
edit: 97 xj. 4.0
Last edited by s346k; 05-22-2014 at 10:51 AM.
05-22-2014, 11:03 AM
#2
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Year: 1999
Model: Cherokee
Engine: 4.0
Dropping to 8 psi within 5 minutes is out of spec however. It should hold to 30 psi for 5 minutes.
Looks like you have a leaky fuel injector or bad check valves in the fuel pump module.
Does the engine run rough when you first start it? Leaky fuel injector(s) will load up the intake manifold with raw fuel and cause a rich start up idle until it clears. If it does look like you are seeing this, you can pull the fuel rail (with injectors attached) back far enough so you can slip some bits of paper towl or clean rags in front of the injector nozzles, then do the prime thing. If and injector is leaking it will show on the paper towl(s).
If they don't leak, think about replacing the fuel pump module.
05-22-2014, 11:59 AM
#3
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Join Date: Feb 2012
Location: central IN
Posts: 2,282
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Year: 1997
Engine: 4.0
48 psi is not high. Spec is 49.2 psi +/- 5 psi.
Dropping to 8 psi within 5 minutes is out of spec however. It should hold to 30 psi for 5 minutes.
Looks like you have a leaky fuel injector or bad check valves in the fuel pump module.
Does the engine run rough when you first start it? Leaky fuel injector(s) will load up the intake manifold with raw fuel and cause a rich start up idle until it clears. If it does look like you are seeing this, you can pull the fuel rail (with injectors attached) back far enough so you can slip some bits of paper towl or clean rags in front of the injector nozzles, then do the prime thing. If and injector is leaking it will show on the paper towl(s).
If they don't leak, think about replacing the fuel pump module.
Dropping to 8 psi within 5 minutes is out of spec however. It should hold to 30 psi for 5 minutes.
Looks like you have a leaky fuel injector or bad check valves in the fuel pump module.
Does the engine run rough when you first start it? Leaky fuel injector(s) will load up the intake manifold with raw fuel and cause a rich start up idle until it clears. If it does look like you are seeing this, you can pull the fuel rail (with injectors attached) back far enough so you can slip some bits of paper towl or clean rags in front of the injector nozzles, then do the prime thing. If and injector is leaking it will show on the paper towl(s).
If they don't leak, think about replacing the fuel pump module.
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