Engine/Transmission (1998.5 - 2002) Maybe LP Problem

[Houser]

Hi

I was just out on a test drive after changing my VP and noticed my LP psi was up and down. Up at cruising speed is about 12-13 and down @ cruising speed is 5-6. I went back to my garage and did the bump the starter LP test. the pump ran @ 15psi then sounded like it was cavitating and the psi dropped to 5-6 just like on the road. Do LPs do that when they go bad or should I check for plugged fuel lines or air leaks or something?



Mike W.

palmer, Ak

 

[DLausche]

The internal bypass could be sticking open. This is not fixable on a stock pump. Also worth checking the electrical connections to make sure there is no issue there. Yes, they often act erractic at their end of life - at least this has been my experience. I doubt a plugged fuel line would be the issue. Just not very likely, IMO. Air would cause it to cavitate I think. I've never experienced this on mine so I'm not sure what to look for signs of it.



-Deon

 

[nps]

Sounds like the LP is getting weak. Mine did the same thing. Rather than changing the LP, I put on a Carter 8psi pusher, and the LP has been happy ever since with 14psi to the VP. Plus the pusher is less $$$ than a new LP - $89 at Summit.

 

[obert]

is that the "blue pusher" ive read about?? Seema a heck of alot more economical than FASS or RASP. I liked the rasp, but my checkbook says save your pennies for a filterless FASS. I dont think My current mods warrant major changes to the fuel supply system.

 

[nps]

is that the "blue pusher" ive read about?? Seema a heck of alot more economical than FASS or RASP. I liked the rasp, but my checkbook says save your pennies for a filterless FASS. I dont think My current mods warrant major changes to the fuel supply system.

No - the blue pusher is a holly pump. The Carter is CRT-P4600HP on the Summit Racing website. Used to be $89, looks like the price went up $3. :{

 

[wlowe]

I installed a carter pusher pump recently because my LP was fluctuating between 6 and 11 lbs. depending on the temperature. Now it runs 12 to 15 at startup and 23 when warmed up. The Carter is 8 psi so now the OEM is putting out 15 in conjunction with the pusher. Initial install cost me around $175 for parts but at $90, pump replacement is much cheaper than Fass or Rasp. Another advantage, if you use a by-pass check valve, is the fact that you always have a pump to limp home on if the other pump fails.

 

[rweis]

To keep the cavitation down, what about installing a tank return line JUST BEFORE the Vp44 input with a bypass valve (like the RASP has, borrow some of the ideas of the RASP without buying the RASP) and set it to 12 psi? You could order the bypass valve only from DTT probably.



That way you know there is good fuel, no cavitation all the way to the VP44, and since the tank return fuel has been filtered you get the benefit of constantly filtering the entire tank, or that part that goes through the bypass valve (and of course the part that goes through the VP44).



Also, you bump the started to check the lp and you get FLOW all the way back to the tank, not just the lp running and maybe or maybe not actually pumping fuel.



Make part of the tubing clear and you can visually SEE if there are bubbles in the fuel.



Just an idea,



Bob Weis

 

[rivercat]

Had a GOOD one yesterday came in,

Whent to dump the water nothing came out, bumbed the starter again nothing. Cranked the truck and then hit the lever and still nothing but it sucked air and the truck cut-off. Perfect sigh of bad LP if fuel doesn't hose out while truck is running then there is no FP if there is vacume from the VP then it will suck air.

 

[MBFARMS]

Just put gauges and the vulcan kit on my truck Sat. Started truck up and 15 psi. I thought alright. Now the last couple of days my gauge shows the pressure dropping to 5 psi and it will stay there for about 30 seconds and come back up 14 PSI. Then last night it dropped to 5 psi and stayed there. I put the truck and neutral and killed the engine. Started the truck back and got 15 PSI. I am thinking my lift pump is going too.

 

[obert]

so NPS, how did that carter plumb in? Im not dead yet, but pressures dont look impressive Im guessing installed near the tank, but how did you put the NPT fittings on the fuel lines?