Engine/Transmission (1998.5 - 2002) Fuel Pressure

[RPA]

Is there a relief valve in or after the VP44 injection pump that might stick open? At startup I have good pressure 16 psi. But, it take very little pedal to really pull it down, and at 1/4 throttle it would run down below 5psi. I thought maybe my pickup was bad of restrictive in the tank so I replaced the stock plastic with a 1/2 steel pipe for a pickup. This helped a bit but still not the answer. So is there a valve the could be open causing the pressure to dramatically fall off. FWIW, relief valve in airdog seems to be working properly.

 

[Steve Campbell]

Rpa

There is a "relief" valve in the return banjo bolt off of the VP 44. I have not heard of it failing as you describe.

When you changed the fuel line... . did you happen to look at the pickup screen in the tank. I have had 3 tanks out so far to clean built up debris off of the "membrane" at the bottom.



I made the assumption here that your fuel filter is clean.



Good luck!

 

[RPA]

Yes, I have replaced both the fuel and waer seperator filters while trying to find my problem. Helped a little with pressure but, is still not correct. Also, I no longer have the screen suction in the bottom, the tube I added is off of the bottom of the tank approx. 3/8" and I plan to install an inline filter when I get this problem figure out.

 

[rweis]

Try taking you fuel feed to the Vp44 off and use a temp hose and return it to the tank and observe the flow. With the temp hose you can put your finger over the return hose like you are spraying plants with a garden hose and see if it continues to put out pressure.



There is a relief valve after the VP 44 vane pump and that CAN stick open, but the pressure is up in the 200+ range. I remember only a single instance in several years of that happening. On a VP44 that valve has zero to do with the OEM lp.



You can do the volume test like the dealer does with the temp hose.



Bob Weis