Engine/Transmission (1998.5 - 2002) Electronic fuel pressure gauge woes

[PatrickCampbell]

I have Geno's 18" hose coming off my fuel pressure check schrader valve and mounted the sending unit to the firewall. Truck is reading 1 PSI at idle, 0 at any amount of throttle... .



Could it be there's a huge amount of air in the line? I just hooked it up with the truck off, and then turned the vehicle on. Thinking back I asked myself where would all the air in the line go when I turn the truck on? When I turn the truck on, that hose fills with diesel, right? How would I get the air out?

 

[Tcolesanti]

I read about this a while back in a thread on here, that somebody had bled the air from the banjo bolt to the sending unit and it had not changed his readings at all. I never bled mine and it works fine, I think after a while the air works itself out on its own, but regardless does not affect readings.

 

[Slightly Modified]

Sounds like the lift pump is gone. I just went to Cummins on Friday to exchange my third lift pump from them, all under warranty thank goodness. This one started declining over the last month. Pressure readings would bounce from 14 to 0 then back up to six and so forth. Put in the new pump and it is solid 14 at idle and no less than 9 with the Comp on 5x5. I would get a new lift pump quickly. Mine was reading 1 psi at idle on Friday when I changed it out. I don't think it was far from dying.

 

[BDMiller]

Air probably isn't the problem however thos sending units don't last forever. I installed my gauges this summer & my sending unit is already acting up. I have a post from about a week ago detailing my problems. But I have a cheap NAPA mechanical gauge which indicates that my fuel pressure is fine. NAPA gauges cost about ten bucks so maybe try that first.

 

[Thomas]

Why would the sending unit "care" whether the pressure it senses is from a liquid or a gas? Many have intentionally (myself included) left air trapped in a short length of hose between the Cummins fuel system and a sending unit for an electric pressure gauge, the thought being that the air will provide some damping action to protect the sending unit from pressure pulses present between the transfer pump and the VP44.

 

[PatrickCampbell]

Should this be hooked up to the fuel filter cannister or straight to the VP44 or does it not matter? I see they both have schrader ports... (?)

 

[Thomas]

If you're interested in post filter pressure (most of us are) and insist on connecting to a Schrader valve then your only choice at the VP44. The other Schrader valve is pre-filter.



If you use a tapped banjo bolt rather than the Schrader then you can obtain a post-filter reading at the fuel filter housing. Some feel that the closer you tap in to the VP44 the more likely you are to damage an electric pressure sensor.

 

[Tcolesanti]

Those shrader valve banjo bolts and the regular banjo bolts are interchangeable, just switch them out..... What's the problem here??? Just put the shrader on the bottom of the filter housing so you don't get pressure spikes from the Vp-44.