Engine/Transmission (1998.5 - 2002) My indications of a bad lp

[Aaron_A]

Before any problems with my lp my pressures normally ran 10. 5 to 11 psi at idle and down to 6 psi at wot. The last time the truck was driven before the lp problem I noticed upon start up that the fuel press. gauge needle was bouncing all over the place,after a minute or so it leveled off at 10. 5 psi and worked as normal.

Yesterday all worked normal even at start up, then when driving to a town 55 miles from home I passed a car and run the truck up to 85 mph,I looked at the gauge and it was bouncing all over again. After a mile or so it leveled off again, but every time I accelerated hard the gauge was erratic. Then on the way back home all was ok until I felt the truck start to surge,I looked at the gauge and it sat at 0 psi . this one wouldnt run for more than about 15 seconds with 0psi

 

[Aaron_A]

I also wanted to mention the gauge is mechanical all the way (fuel to the gauge) sending from the plug on the filter housing. I know,I know fuel in the cab but its a temporary setup and I carry the brass plug and a wrench just in case.

 

[Gary - K7GLD]

I keep harping on this, but have you tried cleaning the power connections to the LP? other than the possibility of fluctuating power, the internal fuel bypass valve going bad inside the LP seems to be the most likely cause...



BUT the fact that your fluctuations mostly occur when making transition from high to low fuel pressures on accelleration/decelleration, makes the valve seem most likely.

 

[Aaron_A]

I wanted to check into it today but with wind gusts of 50mph I think I will just stay indoors. All I know is the pump is not working at all. When it worked I could easily hear it run when the ignition was first turned ,and its silent now.

Tomorrow I will have my meter and I will check for any voltage drop in the connector,but Im sure its the lp.

 

[JR2]

It sounds like the internal bypass, just as Gary said, is going bad. The internal bypass is just a little steel ball and a spring that the pressure overcomes. When the spring gets weak the LP bypasses too much fuel and the pressure drops. I think its time to get a new one.

 

[rweis]

And hence why the external bypass regulator so the fricking internal bypass spring never operates.



Bob Weis

 

[dresslered]

I noticed upon start up that the fuel press. gauge needle was bouncing all over the place

I have one that does the very similar thing. After the truck has been sitting for several days, or it is really cold out, my fuel pressure jumps rapidly from 6-10psi. If I'm not easy on the GO pedal, I could easily pull it all the way down. After about 10-minutes of driving, things go back to normal (it is rock steady). I've already got the spare but just have to find some time to swap it out.