Engine/Transmission (1998.5 - 2002) Wierd fuel pressure issue...

[SLightfoot]

Hey guys - I happened to be paying particular attention to a fuel pressure issue that is interesting.....



I recently installed a new "campaign" pump not more than 3 months ago. Pressure has been good all the time.



Then, one day, I notice the pressure drops significantly, and to the point where if I REALLY lay into the throttle, I can drop it to 0PSI. Not good.



I just replaced this lift pump 3 months earlier... ... I was getting angry.



So I drive carefully for the next several days or so with this lower pressure situation, being careful not to suck it down to less than 5 PSI.



Then, I need to refuel. I fill the tank full of new fresh fuel, and about 30 seconds of driving after filling the tank with fresh fuel, the fuel pressure goes right back to normal.



Never relapsed since.



This was a VERY clear and apparent correlation between fuel and pressure. I had restarted probably 30 times or so since the first low pressure situation, and never saw it come back to normal. Then, 30 seconds of driving after a fresh refill from a different fuel stop, the fuel pressure is back to 100%.



I'm really starting to wonder if some fuels are particularly bad for FP, perhaps foaming or the like.



Anyone ever seen this before?



Cheers,



Shawn

 

[Cummins724]

It is possible that you had a air bubble in the pressure line going to the gauge too. I've seen this happen on a few trucks & the guys thought that it was a lp going bad. Also the fuel filter could have sucked in a piece of dirt & then it cleared out when fuel pressure went back up. The idea of the fuel is possible, but its too hard to tell.

 

[GLASMITHS]

It is possible that you had a air bubble in the pressure line going to the gauge too. I've seen this happen on a few trucks & the guys thought that it was a lp going bad. Also the fuel filter could have sucked in a piece of dirt & then it cleared out when fuel pressure went back up. The idea of the fuel is possible, but its too hard to tell.

This same thing occured to me last summer. Except I would change the fuel filter when it started. So was sure something was in the tank. After the 4th fuel filter I called Chris at Relentless Diesel and right off he says there is air in you gauge hose. :-laf So I got to looking closely at the fuel lines back to the tank (bed tank) and sure enough there was a wet spot on the rubber line from tank to switching valve. So for half the price of a fuel filter I solved the problem.

 

[KTobin]

Boy, you just discribed my problem exactly. except mine would have crappy pressure only in the morning and after work. After a mile, the pressure would come up to 15 again and by the time I got to wourk, it would be back to 20. I figured that I had an air leak and went over the entire fuel system looking for any signs of wet. Nothing! Then I decided to "Keep It Simple Stupid" and bumped the starter a few times when it was cold while sticking my head as close to the lift pump as I could. Bingo! It had a low RPM rattle to it that varied in speed. After running the engine at idle for a while, when the pressure came back, I'd turn it off and bump the starter again. High RPM buzz and constant. 2nd lift pump is smoked! FASS going in tomorrow, I'm tired of waising my money on garbage. I'm not saying that this is definately your problem but it is worth considering next time you see that low pressure and your lines look dry.



Kevin