Engine/Transmission (1998.5 - 2002) Fuel Pressure Gauge is lying to me

[TLadd]

I just replaced the VP 44 injection pump and lift pump on my 01' 3500. The following problem existed before the VP 44 failed. VP 44 failed due to electronics/computer motherboard failure. The problem is is that at idle the electonic fuel pressure gauge (Quadzilla Commander) shows 10-12 psi. When accelerating, the pressure will drop quick and sometimes read 0. When lihtly accelerating or just cruising it will jump around erratically from any number between 0 and 8. When you let off the pedal, it can jump from a flat zero all the way up to 10-13 psi. I have no idea what causes this condition. What are the factors that could cause these symptoms. Any help would be nice. I've read that it could be cavitation and other threads say it is the return valve.

 

[Seafood10]

Hey, not sure of your issue but I have the Edge Juice and my stock pump was showing 5 psi at WOT, I had a Glacier pump installed down on the frame rail just ahead of the fuel cell and now have 20 PSI and havent seen it go under 15, even towing my fiver up a grade. If you mount it lower than the fuel cell you will eliminate the cabvitation. I tried the new replacement Carter pump a few months ago and that crapped out on me. I also just started adding a quart of 2 stroke oil and it really quieted down the engine and added a lot of lubrication to my VP44, worth a try... ...

 

[GCULP]

Where is the sending unit tapped into the fuel system. I had similar issues with just an idiot light setup because I tapped into the fuel line right at the VP44. Try adding a short piece of fuel hose to act as an extension from the fuel system to absorb some of the pulses or you can also try a snubber valve. I believe a snubber valve is needle valve that you basically just crack open enough to allow pressure through to the sender, do a search here and you will find more info on it.

 

[PVanderlugt]

I have found a simular condition on mine, I'm not sure how you have your gauge plumbed but I have found 2 things.
If you are running an isolator and you don't fill the line between it and the gauge with anti-freeze gauge can do some funny things. make sure that you have something in that line(mine leaked slowly thru broken isolator )
If you run a direct gauge with a needle valve play with the valve some. I had the exact same simptoms as you and it ended up being the valve moving to closed on it's own a little. Doesn't make any sence to me but that is exacly what it was. The pulses of the VP can do some strange things to these gauges It is my belief that it also adds to the early demise of our wonderful LP
If you ever wonder, grab the hose in front of the VP while the engine is running.
Thanks Pete

 

[cyborg]

larger (3/8") lines can help provide more consistent pressures.

 

[LXLAW]

I am going through the same thing with my commander right now. I checked it with a manual gauge and it is fine. Quad is sending me a new sending unit to try out. I have a FASS system on the truck, so I know it is doing good and it was a relief when the manual gauge checked out. Hopefully the new sensor will help.

 

[CumminsFarmer]

I run a mechanical liquid-filled 0-30psi gauge directly off the side of the VP-44 where the shrader valve is. It gives me an exact reading of what is at the IP itself. I always get steady smooth readings at all throttle conditions all the time.

 

[LXLAW]

well i have determined that the commander is junk. It doesn't read boost right, it never reads my transmission temp over 100, and even with the new fuel sensor, it reads erratic. it is not very reliable, when dealing with the vp44. I am calling tomorrow to try and get a refund and get some good ol' mechanical gauges.