Care and feeding of the lift pump

[Pit Bull]

Talked with a diesel/mercedes mechanic today and he said that mercedes also uses an external lift pump. He said that the quickest way to kill/damage a lift pump and your injection pump is to run out of fuel and also running low on fuel can wearout a lift pump quickly. He said he would not want to go below 1/4 tank before filling up. Has anyone with failed lift pumps run out of fuel or wait until their tank is close to empty before filling up? Just wondering if this is a contributing factor, or the factor?

 

[Bigsaint]

Well, that's one thing that I can rule out. My truck has never been below 1/2 tank. I could see how it would contribute though, running low may mean more debris coming into the lift pump, while running dry could mean sucking air and causing cavitation and the lack of lubrication for the pump.



Scott W.

 

[Briar Hopper]

I can rule that out, too. I had three lift pumps fail. While running on the fourth lift pump, a #3990105 installed at Scheid Diesel, and on my way home from the Scheid Diesel Extravaganza last fall, I ran out of fuel. (faulty float, unknown to me) Well, I now have an additional 12,000 miles on that lift pump, and it's still going strong. I gave it a heckuva workout, by the side of the road.

 

[Steve Campbell]

I remember all of the talk about how our fuel tank guage is off. I says empty and there is still 6-8 gal in the tank. Maybe DC knew/knows about the lift pump prob and their way of dealing with it was to require us to run around with that extra fuel to keep away from those problems Big Toy referred to. ?

 

[Cliffman]

Fuel left

When my gauge says empty I still have 5-6 gallons left.



Hey Blair, how many miles did you get out of the first 3 pumps before they died? I have 21K on my new one.

 

[Phil Stuart]

Whew!!

FYI,

Once I cut it REAL close and let it get down right on the "E" mark.

I filled up and it took 32 gallons of fuel. So that says all I had was about 2 gallons or so left talk about taking chances!That won't ever happen again.



Phil

 

[Briar Hopper]

Hey Cliffman, I remember you from Tulare. How ya doing? Well, I didn't get very many miles out of those pumps. The first one, original factory unit, was confirmed dead when I got my fuel pressure gauge hooked up. And I had been running around with a PowerEdge and DD3's for months. The second one, bought from Cummins(when dealer monkey made me mad by giving me the run-around) only lasted about 6000 miles. Third one was a freebie, Cummins refunded my $$$ on the one I bought from them. That third one was dead , 8000 miles later when I rolled into Terre Haute, Indiana to have a good diesel party with Dan Scheid & Company. They replaced it under warranty fast, in order to get my truck ready for a dyno shootout.

 

[Todd T]

I run my truck down pretty far before each fillup (i always have) the most i ever put back in was 30 gallons. i average about 28gal.



my first pump lasted 29,000 miles. I'm still on my second with 19,000 miles on it. but it has been assisted by a pusher for the whole time too.

 

[Ramafid]

I fill my tank when I need 30 gallons or more. I usually fill between 30-31 gallons. The most was 34. 5 gallons. I replaced the first lift pump at about 37K miles ( wasn't dead, just weak). The new lift pump is running like a champ with the modifications I have. The first lift pump was on a completely stock engine for the first 36K miles.