Engine/Transmission (1998.5 - 2002) Beating a Dead Horse.........(Lift Pump Woes)

[CumminsPuller]

Well 230,000 miles and about 2 months ago I changed the lift pump for the second time. I checked it today and it was showing 5 psi at idle. Went and bought a new one, just installed and when bumping the starter it shows one or two psi. Once started it takes about 10 seconds for fuel pressure to begin to appear and then another 5-6 seconds for it to reach 15 psi... ..... I would say I just bought another bad lift pump today? Agreed?



Jason

 

[Turbo Tim 1]

Or maybe a suction line that's just a little loose allowing air in the system???? Just a little guess.

 

[CumminsPuller]

Tim, where do I find these suction lines... ... ... ... Do you mean the lines coming from the tank? Anyway to verify that without throwing parts at it?



Jason

 

[Turbo Tim 1]

Yes exactly, when my pump got changed under warranty the guy didn't have the lines tight enough and had an awful time getting things primed again even though nothing was leaking. He went back and put a wrench on everything and found one connection quite loose, tightened it up and away she went.

 

[Turbo Tim 1]

Check from the fuel filter to the lift pump and the connections from the lift pump towards the tank, it should only be things you disturbed changing the pump. It is quite possible you got a bad pump though. Does the pressure stay good going down the road after it finally gets to 15 psi? If so I would be hesitant to jump on the bad pump theory and more of an air pocket or leak theory.

 

[CumminsPuller]

I just went and double checked the lines and everything is tight. You can tell once the pressure comes up the truck is happier. Re-checked the connections, everything tight. Those are the only three I touched. Just ran her down the road at WOT and it dropped to 11. 5 psi... ... ... ... My guess is the pump is good and air is getting in somewhere.



Jason

 

[CumminsPuller]

Now the air pocket theory... ... . After the change she fired right up despite the line from the pump to the filter being removed. Not a stutter at any time. Could there still be an air pocket in that line or the fuel filter?



Jason

 

[Gary - K7GLD]

NO worries - just an air bubble in the fuel pressure line while doing the swap - betcha everything returns to normal in a couple of days...

 

[Texas Diesel]

I wonder if the intank strainer (very fine mesh) is clogged? You need to do a vacuum measurement on the tank side of the LP. There is some sort of DC spec for it but cant remember.

 

[daveshoe]

Originally posted by Gary - KJ6Q

NO worries - just an air bubble in the fuel pressure line while doing the swap - betcha everything returns to normal in a couple of days...

Gary, don't forget your past advice on putting electrical contact grease on the LP connector when changing pumps. Prolly dosen't apply to this one ,but a good tip to remember

 

[CumminsPuller]

Thanks all... ... ... I will run it for a few days and see what happens... ..... Atleast I can return the one that I installed back in January and get my money back. I just hate starting it and knowing the VP44 isnt being assisted for about 10 seconds. What was the deal with the electrical grease? I know what it is for but was there an "incident" that required it?



Jason

 

[Gary - K7GLD]

The grease is a sealant/contact enhancer that is intended to prevent oxidation of electrical contacts and assist current flow due to cleaner contacts - the grease itself is not an electrical conductor as far as I know...

 

[CumminsPuller]

Update...........

Today the truck started just fine in the morning... ..... drove for awhile around town without turning it off. Went to get my haircut. Came out of the hair place and truck would not start. tried for several hours to start, no go. Had a buddy tow me to the local dealer. Plugged in their computer, code 0216... ... ... I think ya'll know the rest of the story.



Jason

 

[Gary - K7GLD]

Keep us posted...

 

[CumminsPuller]

Scheduled for an injection pump change in the morning... ... ...



Jason

 

[CumminsPuller]

Out of curiosity, are there some kind of new specs on these injection pumps? I was looking at Piers site and it mentioned something about the rebuilt ones being built to 027 specs? What were the specs before that? What has changed, what is different?



Jason

 

[Gary - K7GLD]

I'm bad with numbers, but there are *2* models of VP-44's used in our trucks, one for the standard output engine, and another - I think the 027 - for the HO version... Basically the same pump, the one for the HO just puts out a bit more fuel volume...

 

[CumminsPuller]

I am sorry I did not get back to ya'll about this. But remember I was getting bad LP readings, even after installing the new LP... ... Well after the new injection pump went in all is well. What I can not figure out is how a bad or going bad injection pump will mess with LP readings?



Jason

 

[Sticks]

Originally posted by Gary - KJ6Q

I'm bad with numbers, but there are *2* models of VP-44's used in our trucks, one for the standard output engine, and another - I think the 027 - for the HO version... Basically the same pump, the one for the HO just puts out a bit more fuel volume...

Nope.



Believe it or not, the SO version puts out more fuel. All the power in the HO's comes from the computer programming, and higher compression. The SO's even have larger OEM injectors.



Tests have been done putting a SO VP44 on a HO truck, with little or no gains - go figure.

 

[Hohn]

Originally posted by Gary - KJ6Q

The grease is a sealant/contact enhancer that is intended to prevent oxidation of electrical contacts and assist current flow due to cleaner contacts - the grease itself is not an electrical conductor as far as I know...

Dielectric grease is actually an INSULATOR! It works by making sure that the only electrical path is that which has mechanical contact, helping to prevent stray shorts and such. It's also for preventing corrosion, etc...



jlh