XJ XJ8 / XJR ( X308 ) 1997 - 2003

Fuel Pressure Spec for 99 XJ8?

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Old 03-19-2011, 08:33 PM
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Default Fuel Pressure Spec for 99 XJ8?

Anybody have the spec at Idle and WOT handy?
 
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Old 03-19-2011, 08:47 PM
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40-41 psi above manifold pressure.
 
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Old 03-20-2011, 10:50 AM
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Thanks Sparky!

At WOT I've got 41 psi solid as a rock. I know vacuum will be next to nothing at WOT so that one looks good to me.

At Idle and part throttle I've got 34 psi.

I'm without a vacuum gauge so does the idle reading sound about right?
 
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Old 03-20-2011, 12:21 PM
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Well, a 7 psi drop would match 14" of mercury which seems like a reasonable vacuum reading at idle.
You did not ask, but the fuel pressure at WOT UNDER LOAD can drop off due to the pump's inability to supply volume. What you have proved so far is that your regulator is working fine, and the pump can supply pressure at low volume. To test under load, I use a long hose on my fuel pressure guage, with the guage taped to the OUTSIDE of the windshield, then go for a drive.
 
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Old 03-20-2011, 07:42 PM
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Yep. My 41 PSI figure was with the accelerator mashed to the floor going up a nice steep hill. I had the gauge zip tied to the windshield wiper arm.

Thanks for the conversion on the Idle pressure.

Ken
 
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