Engine/Transmission (1998.5 - 2002) Fuel pressure cold vs hot numbers

[JCyrbok]

I'm sure this is the case, but my fuel pressure numbers increase as the engine warms. Anyone else?



When engine is cold ( either sat over night or actuall temps outside are cold) I get 12. 2 at idle after the grid heaters run their cycle. After engine runs for about 10 minutes that increases to anywhere between 13. 0 and 14. 0 at idle.



If I park and the restart a while later the pressures stay up in the 13's at idle.



The cruising pressures have about the same swing with the temps.



I dont know what WOT is cold as I dont step on it hard until the thermostat has opened atleast once.



ANy thoughts. I think it has to do with the higher the temp higher the pressure rule from physics ( I think thats bernoullies law?)



Also anyone else see FP drop acouple of tenths when the grid heater cycle. Mine does but comes right back up when they cycle off.



Thanks

J-

 

[Steve St.Laurent]

Yep - totally normal. Look at your voltmeter on the dash as your grid heaters cycle and you'll see why. The grid heaters pull 110 amps :--) ! That's a BIG draw on the system and why you have two batteries. You'll see the voltage go down around 11 volts when the heater grids come on. A second thing is that diesel fuel gets thicker as it gets colder, you will see slightly lower fuel pressures on cold days until the fuel warms up.

 

[tarussell]

Sounds normal to me... ... . My pressures read just like yours,Thomas

 

[JCyrbok]

Thanks

Cool Thanks guys thats what I thought. But sometimes it helps to hear that others think that too.



Thanks

J-

 

[andrewkoperdak]

Since I got my new lift pump I see X>15 psi. I only have a 0 to 15 gauge and it goes past 15 at idle unless the grid heater is running. When grid is on it draws so much current it affects my fuel pressure gauge. Cruising I hold a solid 14 psi. None of these numbers worked for my original lift pump. I could only have 13 at idle and about 10 running on the highway. Eventually that 10 went to 3 and went to 0 and that is went my lift pump got replaced. My sickly LP would run lower pressure as the fuel in the tank got warm.

I was stock when I had my original LP.

R,

Andy