Engine/Transmission (1998.5 - 2002) Lift pump argument

[WBlackburn]

I have an 01. Having read all the posts about the LP problems I related this to a friend. His 01 has about 76k & I mentioned he maybe should have it checked because he has no gages. He checked with a mechanic that told him that was all BULL. The LP was electric and when it quit the engine would not run, just like a plugged fuel filter.



Who's correct here??

 

[csutton7]

Definitely not the mechanic--the VP44 can pull fuel thru the lift pump to keep the truck running, it's happened more than once---what usually happens when it goes out is the truck becomes more difficult to start and maybe stumbles on hard acceleration--tell your friend to take it somewhere else cause this mechanic is in gasser mode--chris

 

[B.G. Smith]

Originally posted by WBlackburn

I have an 01. Having read all the posts about the LP problems I related this to a friend. His 01 has about 76k & I mentioned he maybe should have it checked because he has no gages. He checked with a mechanic that told him that was all BULL. The LP was electric and when it quit the engine would not run, just like a plugged fuel filter.



Who's correct here??

It ain't the mechanic. Mine quit, "0" pressure, had it towed to dealer, they kept it a week, got it started and I brought it home, still zero pressure, called another dealer with some Cummins experience, he picked it up with wrecker and changed transfer pump that afternoon, presto, fuek pressure again. bg

 

[Sticks]

Find a new mechanic. LP can be dead, and the VP will keep the engine running, while committing suicide at the same time. Then you have a truck that could have been fixed for $150, and now it's closer to $1700.

 

[tbrudder]

Ditto all the above. Mine died one day while I was pulling in to work. No warning, just died when I pushed the clutch in at a stop sign (no gauges at the time ). Towed to dealer--bad LP. Replaced it, wouldn't start--dead VP-44.



Yeah, it was under warranty, but with a '99, that's almost spent now. I've heard from $750 (doing it yourself) to $3000+ (for the dealer) to replace the injection pump.



Gauge is cheap insurance, so is a mechanic who knows his business--good diesel mechanics seem to be harder to come by.



--Ty

 

[BarryG]

Another case of an uninformed or misinformed mechanic. It may be true for certain types of fuel pump/systems but certainly not this one. I have had gasser electric fuel pumps go out and yes when they quit they just wont go but since the vp44 has its own internal fuel pump which just isn't up to the task of keeping it cool and lubed it can keep running as long as the lift pump hasn't shut the flow of fuel off. Another item of note is that many of our bad fuel pumps dont quit completely they just don't flow enough for the cooling and lubing of the 44 causing it damage or it not being able to provide sufficient fuel flow under high fuel needs situations hence the bucking etc.

 

[DSpencer]

engine will run with no lift pump

At 58,000 miles, my engine just did not feel right. Didn't feel as powerful as normal. I had already read the lift pump posts but never checked. I bumped starter, no noise from pump. Again... . nothing. Took it to my dealer, HAD TO EXPLAIN THE DIFFERENCE BETWEEN A LIFT PUMP AND INJECTOR PUMP TO SERVICE WRITER AND SERVICE MANAGER BEFORE THEY WOULD LOOK AT IT... I felt like they knew what I was talking about. After convincing them that I knew what the potential problem was, the service manager acknowledged that he knew what I was talking about. When he heard that I had gotten my info from a website, he told me that the lift pump was actually not a big problem but would look at it anyway. He also said not to believe anything I heard on the internet as THEY didn't know what THEY were talking about.



15 minutes later, the manager came and told me that the computer showed that the lift pump was not working at all. They changed it in warranty and said sorry.



Sorry about my ranting but the engine will still run sometimes without a lift pump.

 

[ntillm01]

Ditto

Personal experience: Lift pump quit working, pump motor did not run at all. Had stumbles on hard acceleration, especially turning left (we have those infamous Michigan left turns here ) so I noticed something was different. After putting a new one in, the stumble was gone and performance picked up a bit.



Yes, the VP44 has a low-pressure "lift pump" internally. I believe some applications using the VP44 don't have an additional lift pump externally. These trucks need it because of the distance from the fuel tank, it seems.



Diesels are super-mysterious to the majority of technicians at dealerships. I was just explaining to one the other day that glow plugs aren't what "sparks" the fuel in the cylinder. He was trying to understand how mine could run without glow plugs.

 

[Texasdeere]

That's scary, God forbid I should ever have to take my truck to the dealer to get the engine worked on!

 

[Makensmoke]

I'd bet a small air leak between LP and VP would make engine stall as soon as LP takes a hit. When the LP is working it can push fuel thru or past a small leak, but when you have a negative pressure there i'd bet she'd suck air and then stall. Just my brain storming and something you might want to check. I've noticed the factory hose clamps are junkie.

 

[JWhitcomb]

These stories about dealers and what they know never fail to scare me. I carry a spare LP but mine still shows fair pressure at 35K.

 

[CFowler]

i was basicaly carried out of the dealers shop when the mechanic? and i got into it. he wouldnt believe my fuel pressure guage . and didnt know what to do with his,untill i told him where to stick it! next day they did replace the L/P.

 

[CraigZi]

Mine died completely at about 60K. I can't really say I had any warning. I got towed to a dealer who knew exactly what I was talking about and had me back on the road with a new lift pump in about two hours. I now have a guage and I'll be watching for a change in pressure and be ready for the inevitable next time.

 

[Mad Bomber]

PSI

Originally posted by JWhitcomb

These stories about dealers and what they know never fail to scare me. I carry a spare LP but mine still shows fair pressure at 35K.

Mine went @ 36. 6K so keep it close by. BTW It's alot faster to just change it your self AND it's done right

 

[RobertMiller1]

lift pump elimination

Somewhere in one of these archived posts, a knowledgeable Cummins rep is addressing the lift pump issues in these trucks.



he mentions the VP44 is much stronger than we would think, and he goes on to mention there are several 6bt vp44 configurations that do not utilize a lift pump.



What about running with straight line to the tank without a lift pump?



I know in my trooper the Bosch VE does not have a lift pump. Most diesel pumps (and the VP44 is not different) have a low pressure input pump for drawing fuel from the tank.



It seems the biggest hazzard is when the lift pump fails, and it subsequently blocks fuel delivery to an extent that damages the VP44.

 

[merryman]

There are failures and then there are failures.



In my case, the truck suddenly started running very poorly--missing, stumbling, no power -fuel pressure at zero. Stopped and shut it off for a few minutes and when I restarted it all was well; pressure was back to normal (15 Psi guage pegged at idle and not below 6 psi a WOT. It ran fine for 20 miles then repeated the problem. Got to a garage and all was well again.

Thought maybe a plugged filter. Changed that and all seemed well. Drove for another 40 miles with normal pressure and running, and then it did it again. Changed out the lift pump and no more problems now for about 1500 miles.

BTW, I disected the pump and found a small square metal chip lodged in ball valve.

Vaughn

 

[Makensmoke]

The guage is a fuel pressure guage plumbed in after the lift pump to monitor how well its working or not.

 

[ntillm01]

Robert Miller1: I agree. I believe the lift pump helps ensure fuel delivery, and provides a nice prime when the key is first turned on. When it doesn't work, it is in the way of the fuel. In some cases, in the way enough to keep the engine from running.



I read up on the Bosch injection pumps and all the rotary-type have their own built-in low pressure pump that can pull fuel directly from the tank. They are also very specifically sized, depending on the HP/cylinder they're getting bolted to. A smaller engine doesn't need as much fuel per cylinder, so the amount delivered is less critical than, say a 235 HP cummins. Could be the reason the lift pump was put on these trucks.



Random thoughts...

 

[RobertMiller1]

failproof design

Well,



Seen many race cars that had dual electric fuel pumps in back fed into a regulator and then filters.



Dual pumps were in parallel. and redundant.

 

[CFAR]

The VP44 is also cooled and lubricated by diesel. So just because the VP can suck enough fuel to run the truck doesn't mean it can suck enough to also cool and lubricate itself.