Engine/Transmission (1998.5 - 2002) replacing lift pump wire harness

[mmclaughlin]

I replaced my lift pump about 4k miles ago, and now I'm thinking that I need to replace the wire harness. I changed the fuel filter this evening, and I noticed that when I bumped the starter, the lift pump came on, but when I tried it a second time, nothing happened. Did it a few more times and nothing. The truck started right up and I ran it for awhile, then shut it down. I let it cool for awhile and tried bumping the starter - nothing. So I grabbed the new wiring harness that came with the new pump, and I was going to change it out. Problem is that I can't seem to get to the connector because of all the tape that's on all the wires. So I desided to clean up the old connector the best I could. After cleaning and reinstalling, the pump seemed to work fine. But I still want to replace the old wiring harness. So I started to take off the old one by removing all the old gummy electical tape that was on the lift pump wires. I only made it to the point where the lift pump wires enter into what seems like a larger wire harness. Is the other end of the connector in that harness somewhere? Is it easy to get to? I spent a little over an hour trying to get that old electrical tape off, with very little luck. It only took 45 minutes in a snow storm to replace the pump, now this little wiring harness is kicking my butt - am I missing something here? Thanks for the help.



- Mike

 

[mmclaughlin]

Anybody have any thoughts on this? I bumped the started this morning and the pump ran just fine, but after I got to work (about a 45 minute ride) I turned the truck off and then I tried to bump the starter - and no pump! I'm convinced that it's the wire harness. Has anybody taken out the old wire harness on a 2001 lift pump, or does everybody just use the old wire harness?



- Mike

 

[Thomas]

The "harness" that you were sold with the transfer pump is just an extension needed when installing the transfer pump on model years 1998 and 1999 Rams. Model years 2000, 2001, and 2002 do not need the extra wire length. I suggest you stop removing the tape on the OEM harness.



Do a search using pigtail if you want to read about what years need the extension, part number for the extension, part number for the transfer pump alone, and part number for the transfer pump/pigtail combination.

 

[mmclaughlin]

So for 2000-2003 trucks, you cannot replace the harness? You have to use the orignal one? The reason why I ask is that I believe my connector that goes to the pump may have a bad connection. I have this harness that came with the pump, and I want to replace the actual harness. Does this mean that I have to cut the harness that I got with the pump and then cut the original harness to put the new connector on? Thanks for the help.



By the way, I think at this point it would be easier to cut and reconnect the harness then try to remove all that tape! Any suggestions on the best way to do this?



- Mike

 

[Thomas]

The pigtail that came with the replacement pump is just a short "extension cord" needed 1998-1999. If you continue to remove the tape you will never find that pigtail on your 2001 Ram.



If you are convinced that you need to change the connector that attaches to the transfer (lift) pump, cutting and splicing is what you will need to do.



Before I cut up the wiring on my truck I would put a gauge on the low-pressure fuel system and see what fuel pressures are present at various conditions.

 

[mmclaughlin]

Thomas - thanks for the info. I guess I'll just cut the old one off an attach the new one. I don't have a fuel pressure gauge, but it seems that the pump will work some of the time and sometimes it doesn't. The only way I have of knowing if it works or not is by bumping the starter. Sometimes the pump works like a champ, sometimes I get nothing. When I get nothing, I disconnect and clean, then reconnect, and it usually works again.

 

[Blue2002]

My thoughts: After cleaning your electrical connections, use some dielectric grease when you reconnect the plug. That will help to eliminate any possible corrosion issues. I would try to eliminate all possibilities before cutting/splicing any wiring. Maybe borrow a multimeter to check for the voltages on the plug.

 

[krs]

isn't it the case that the liftpump only operates for starting for a very short time to build initial pressure and does not run at all if there is already sufficient pressure to the vp44?

Maybe there's nothing wrong with your truck?

 

[mmclaughlin]

I thought that the lift pump ran all the time? I used to be able to bump the starter, and it would always run for the 25 seconds. I would really like to avoid cutting the wires, I'm going to try to clean it out really good and then apply an electrical grease and see how that works.



One other question for you guys out there - is the pump you get from the Cummins dealer any different then the one you get from the dealer? Is there a way that the dealer can tell if you have a Cummins pump in? Thanks.



- Mike



playing in the snow and not at work

 

[Thomas]

Originally posted by KRS

. . . and does not run at all if there is already sufficient pressure to the vp44

Any pressure built up by the transfer pump is quickly lost if the transfer pump is not running. If the starter is "bumped", a gauge mounted in a properly functioning low-pressure fuel system will show a quick pressure rise to 15± psi. The pressure will be steady until the transfer pump stops running, at which time the pressure will quickly drop to zero.

Originally posted by mmclaughlin

I thought that the lift pump ran all the time?

The transfer pump runs all the time the engine is running, for two seconds when the key is turned from the off to the run position, and for up to twenty-five seconds when the starter is "bumped".



The difference in the transfer pumps from D/C and Cummins is the price.

 

[Gary - K7GLD]

The lift pump only runs briefly when the ignition is first switched on to prime the system - the VP-44 will NOT start if it sees PSI above about 7 PSI on *initial startup* - once started, obviously, it runs at higher pressure. This is why guys installing pusher pumps must tie into the stock pump to trigger operation of the pusher - otherwise, if they have the pusher run continuously when the ignition is switched on, the truck won't start due to too high PSI to the VP-44.



Sad that DC/Cummins uses those miserable connector types for the VP-44 - the contacts are way too small for their intended service, and their construction makes them hard to clean properly - I've had similar problems with the same type connectors on the oil pressure sensor on my old '91...