Engine/Transmission (1998.5 - 2002) Pusher lift pump installed - lift pump demon is slain (hopefully)

[WestTN]

Steve, wouldn't their recommendation be for 3 feet of head maximum? Pumps are usually rated that way. Unless the feedline is quite a bit undersized it shouldn't matter a lot how far away it is. ( Some head pressure reduction would occur due to acceleration. )

 

[Steve St.Laurent]

No, their directions call for it to be mounted within 3 feet of the fuel source.

 

[wicked6]

Steve, wouldn't their recommendation be for 3 feet of head maximum? Pumps are usually rated that way. Unless the feedline is quite a bit undersized it shouldn't matter a lot how far away it is. ( Some head pressure reduction would occur due to acceleration. )

I was wondering the same thing. . The stock lift pump should have a rated "suction head" (NPSH), and unless you have excessive pumping loads (clogged screen, cavitation, lots of bends in the supply line, *cold* fuel, or changes in tubing diameter) it would seem the stock lift pump should be just fine. . DEPENDING on it's NPSH rating, of course..... Anyone got that figure handy. . ???



Since I don't get to do any engineering at work, I get to do it vicariously through my hobbies! :-laf

 

[AlFischer]

Steve, I installed a Carter P4600HP as you described at the tank and relocated the original lift pump to the frame. The Carter is relay controlled as you described. Got 10-19 FP sometimes just about 21. Shortly after, I started to notice a 'stumble' when starting. Took maybe 2-3 cranks to start mainly when restarting after engine is up to temp. Have never seen it go below about 16-17 WOT. Drove about 15,000 miles and started to get P1693-0216. Reset several times and it appears to reoccur on start. The shop manual mentions the overflow valve sticking open can cause starting problems as it can drain the VP44. Also noticed when I installed it that upon key on the pump ran for about 1/2 sec and pressure only went to about 2. If I then bump the starter it will run the prescribed 25 sec and FP goes to 18.



I firmly believe the VP44 may be the most unreliable component of the truck. My concern is: Is the higher pressure the cause of the stumble and could it be responsible for any damage to either the overflow valve or the VP44? The truck now has 75K miles and the original lift pump was replaced after relocation due to a small leak probably caused by the change to ULSD. The new pump is a campaign pump and the pressures did not change from the original pump.



I expect the VP44 is going out to lunch and I will be replacing it soon. Should I take steps to lower the FP? Should I possibly also put in a new overflow valve?



Truck is stock except for full gauges, a trans fan-cooler, and the pusher pump setup.

 

[Misenheimer]

Steve

Nice article. I am going to use the Geno's kit with a stock lift pump cause I have a stack of the stock pumps that are good and the Geno's kit is $65 or so. To keep the noise down I am going to use Mercedes air cleaner mounts. They should work fine cause the Mercedes air cleaner is heavier and shakes more (5 cylinder). For safety I might put in two 1/4 bolts through the mount and frame rail with self locking nuts and not tighten them up so if a rubber mount fails then the pump won't fall off. I also plan to take a longer piece of 3/8 hose to bypass the pump if it fails.

Thanks again

 

[Steve St.Laurent]

All I can tell you is my experience. I now have 230,000 on my truck with the original VP44 in it. I've been running the pusher pump setup since 65k with 20 psi of fuel pressure that entire time. The only problem I've ever had is I have to wait for the pumps to shut off after turning on the key before I crank the engine otherwise it takes a couple seconds to start. As long as I wait for the pumps to stop before I crank it lights right off.

 

[Cliffman]

I now have 230,000 on my truck with the original VP44 in it.

Wow Are going to run it till she dies? I have 193,000 and feel like I'm on borrowed time.

 

[Steve St.Laurent]

Of course I am!!

 

[AlFischer]

When you first turn the key on how high does the pressure go if you don't hit the starter? Mine seems to be a max of about 2 PSI and the pump seems to run only about 1/2 second instead of the expected 2 seconds.

 

[Steve St.Laurent]

Depends on the temperature outside but in warmer temps it goes right to 20 psi.

 

[Huff N Puff]

I was wondering the same thing. . The stock lift pump should have a rated "suction head" (NPSH), and unless you have excessive pumping loads (clogged screen, cavitation, lots of bends in the supply line, *cold* fuel, or changes in tubing diameter) it would seem the stock lift pump should be just fine. . DEPENDING on it's NPSH rating, of course..... Anyone got that figure handy. . ???



Since I don't get to do any engineering at work, I get to do it vicariously through my hobbies! :-laf

Mopar goofed big,when they put the pump high up on the engine,and supplied it with a restrictive fuel module in the tank and tiny fuel lines. That is why Mopar moved the redesigned pump into the bottom of the tank. So now it does not draw thru the module,and it just pushes thru the small lines.

 

[Cliffman]

Mopar goofed big,when they put the pump high up on the engine,and supplied it with a restrictive fuel module in the tank and tiny fuel lines. That is why Mopar moved the redesigned pump into the bottom of the tank. So now it does not draw thru the module,and it just pushes thru the small lines.

Yah, so how come some still fail after 20-30k after the relocation to the fuel tank? What a disaster! I can't believe that Mopar can't get this thing figured out. It's been a problem since the beginning of the 24 valve and the VP-44. after all, fuel delivery is rather important especially when/if the injector pump is fuel lubricated.