Bought the truck two days ago. 99 24v with 273K. Has Air Dog II lift pump. First day i drove it 100+ miles and it stayed at a consistent 15psi while driving. Today, i noticed it down around 11-12 psi and this evening, it started fluctuating rapidly between 0 and 12 psi. Any ideas on what could be causing my problem?

 

Sounds like "water hammer". Read this article Mopar1973Man's Dodge Cummins Articles - Fuel Pressure Gauge And Water Hammer Effects Is it a mechanical or electric gauge?

 

It's a mechanical gauge. I forgot to mention too, the truck idles erratically during this and acts like it wants to cut off until i start rolling again. Once i get up to speed, it holds a consistent 10psi.

 

filters...

 

I tried to get a new filter and water separator today but NAPA doesn't stock them so I ordered them and they'll be here Monday. Could the filters cause such a dramatic drop in pressure?

 

Yes clogged filters can. How much fuel do you have in the tank?

 

just shy of 1/2 a tank.

 

If you have a truck stop near you check and see if they carry air dog filters. Some of them do.

 

Didn't think about that, will do. Thanks! Are the fleetguard filters of the same quality as the Air Dog part?

 

Fleetguard is good. Not sure if they will fit without slight modification. I know with a Cat filter part of the bracket has to be ground away because the Cats are slightly bigger. The fuel gauge in our trucks are notorious for being inaccurate. I'm empty when my gauge reads 1/4 tank so you might want to fill her up and see how many gallons she takes. Should be a 34 gallon tank.