Engine/Transmission (1998.5 - 2002) Lift pumps bad. Why?

[lkozark]

My local DC dealer also has a Freightliner shop next door. I took my truck there for a couple of issues which they took care of. During the course of my visit I got a chance to talk to the Service Writer and the mechanic about the ISB's lift pumps. This what they told me. The lift pumps have been problematic, (we know that). Their experience has been that the failures seem to be caused by contaminents the fuel tank getting into the pump and damaging the impeller and/or blocking the screen on the inlet of the pump. Theysuggested a pre pump filter might help with the problem and changing them frequently.



Which pre filter to use? They said any large gasoline in-line filter available from your local parts store. Mount it as close to the stock filter and where it would be easily accessable for replacement. Also, mount the inlet/outlet horizontal so it might trap any water.



Sounds reasonable to me. Has anyone tried this?



Also, they said that the ISC 8. 3l only uses the lift pump at start up and then on the VP44 handles the fuel draw. How I asked. They said the VP44 has the ability to draw it's own fuel from the tank after start.



Now you see why I am confused.



Happy Holidays from Lake of the Ozarks, Missouri.



2001. 5,SLT,QC,stock,auto,deer killing Manick brush guard, Westin nerfs,BFG 285A/T's,Topper

 

[BillGotthelf]

You don't hear much about it but my 96 went thru 2 lift pumps (mechanical) in the first 60,000 miles until Cummins put one in and its still going strong after 150,000 miles. It seems to be the luck of the draw. I know people who have never replaced their lift pumps and have 100,000 + miles. Go fiquire

 

[swalls]

The 8. 3L ISC does have a small electric lift pump similar to the ISB. It does only run 30 seconds after ignition on. But the ISC has a completely different injection pump, not even similar to the POS VP-44. It's called a Cummins Accumulator Pump System or CAPS. That huge 85-lb pump contains a mechanical spur-gear fuel transfer pump that is easily capable of approx 15 gallons per minute at 150-180 psi. The only purpose of the electric pump is to purge the suction side of the CAPS system and provide a momentary positive pressure to the inlet of the mechanical lift pump. Once it takes hold, the CAPS lift pump is capable of sucking 1/2" rubber fuel lines shut if they get a kink in them. (About the only problem is that it is so powerful it can suck air through well-sealed fittings if you get some kind of fuel inlet restriction. ) It retails for roughly $3750. 00 , and is completely rebuildable at the dealership level. Earlier versions had some startup problems, but the ones produced since late 2000 are extremlely reliable. You get what you pay for, I guess.

 

[GLASMITHS]

Originally posted by BillGotthelf

You don't hear much about it but my 96 went thru 2 lift pumps (mechanical) in the first 60,000 miles until Cummins put one in and its still going strong after 150,000 miles. It seems to be the luck of the draw. I know people who have never replaced their lift pumps and have 100,000 + miles. Go fiquire

I have 100,200 miles on mine. Still has 12. 5# idle, 9. 5# cruise and 6# wot (on the floor towing). From all the posts over the years I believe that the MAIN reason for failures is the position of the pump. The unfiltered fuel may not help. I have always used power service (double strength) and never run the 95 gal tank below half.



Sometime in the future I plan to put it all on the frame with a Racor prefilter; already have everything, just hate to fix something that isn't broke, yet. BTW I get 1-1. 5# more pressure from the bed tank than stock tank. It does not have to pull as much.

 

[Steve St.Laurent]

At least in my case the cause of the failure of the lift pumps on my truck was due to the location of the lift pump it having to suck fuel from so far away. I bought my truck with 24,000 miles on it. It was my first diesel ever so I knew nothing about the maintenance of it. At 28,000 miles I had a cummins dealer install a prime-loc fuel filter on it and the mechanical had a heck of a time getting the truck restarted - took him an hour and a half. This was before the lift pump problems were known - late 99. When I had about 38,000 miles on the truck the lift pump recall came out for the 99's and my truck wasn't within it but recalling the problem starting it after the filter change I put a fuel pressure gauge on the truck and to my horror found that I had 0 psi of fuel pressure even at idle. I had no idea how long it had been bad before that. I replaced the lift pump then and between 40,000 and 60,000 miles I replaced 4 lift pumps all due to low pressures which were initially fine! When I changed that first lift pump I also drilled out my banjo bolts to help with fuel flow. At 60,000 miles I was sick of replacing lift pumps and researched options.



I bought a 7 psi carter pusher pump from Enterprise Engine ( https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=19767 ) and put that on in addition to a new OEM pump at the engine. That was in June of 2001 and at that point that OEM pump was the 6th OEM lift pump on the truck! Now I have 140,000 miles on my truck and I haven't replaced another pump since. Nothing else changed on my truck or my usage - no additional filters, no change in where I bought fuel from, etc (other than that I've cranked up the power even more since then). So IMO at least in my case the primary cause for my failures was the location of the factory pump.



JMHO