jec3

I posted earlier in the week problems with truck stalling and suspected bad lift pump. Well I just came in from installing my gauges (fp, pyro, boost) and here is what is going on. I start the truck cold get approx. 14 psi fuel pressure within a minute pressure drops off to 0 (LP shuts off). I turn it off and turn the key and no noise from LP and no pressure. I let it sit a while and up to 14 psi for a min and then off again.<br><br>So when the LP is running seems to be good pressure but then just quits. Usually I read LP drops psi steadily until it's under spec then is replaced. Have not read about any doing what mine is doing? I checked the connection all is clean and good. <br><br>My question is does this sound like just a bad LP motor or is there a relay i should check. Since something turns the LP off after you turn the key and lets it run for 15 seconds or so or until you start it, could whatever this is be the problem instead. Hope that makes sense. <br><br>Thanks in advance<br><br>P.S. Love my new Rod's Pods and guages 8)...wish I could drive her around and see them work

jec3

Another quick thought, any chance the EZ has anything to do with it. I didn't try unplugging it, should I???

jec3

Read through the service manual last night and found the LP is controlled through the ECM. So I am hoping my problem is not with the ECM (or EZ interacting with ECM). Will order a new LP today and hope this solves my problem. Seems by the lack of response no one else has had these symptoms...I'll report back later in the week after new LP is on what I find.

AlpineRAM

jec3: I would check the lift pump feed cables with a voltmeter. I replaced the stock pump with a holley blue in the frame rail at the tank. I run a relay that is driven by the ecm output and switches current from the battery to the holley.

If there is voltage to the pump and there is no pressure- bad pump. If there is no voltage- bad ecm. ( If out of warranty you can make a simple switch and forget about the ecm replacement)

HTH

AlpineRAM

jec3

Thanks Alpine, good idea, I will try and monitor voltage to LP and see if ECM is shutting off power or if LP is shutting off even thought power is available...

jec3

Follow up FYI - Replaced the LP last night and all is well. Motor must of gone bad in the old one, strange symptoms though. I may disassemble the old LP and see if I see anything obvious. Wish Cummins/Dodge would do something about this LP design, so many consistent and varying problems.<br><br>Installed the larger banjo's while I was at it and now getting a steady 16 psi at idle. Hopefully won't have to worry about this again for another 68K but may purchase a backup and carry it with me for peace of mind...

BigBlue

The backup is a good idea. Or you could install a Holley Black or a PE4200.

Dieseldude4x4

I tore the pump end of my old one a part. There was nothing wrong in the pump end so the motors must be going bad somehow.

cr1998

I haven't been on here much lately, due to work, but I seem to recall a post several months ago about someone taking the bad pumps apart, changing some little something inside, and getting them to work again. Anything ever come of that?<br><br>CR

BigBlue

I know the post you are talking about. Something about flipping a gasket or something like that. Haven't heard anything about it since then.

jec3

Here's that thread:<br><br>http://www.dodge-diesel.org/yabbse/i...d=8212;start=0<br><br>I don't think that was my problem since mine seemed to be related to the LP motor not pump mechanism...

jec3

Here is an interesting thread if you are curious:<br><br>http://mailman.greenberg.org/piperma...ly/000174.html<br><br>

moopa

jec3,isn't that pump still under the cummins warranty? i thought you had 5 year/160,000km on it?

jec3

Yup, warranty is relative to the dealer tho. Had my ckp go bad took it to them and they said it's not covered. That d*@m part is an integral part of the block! If my local dealer won't warranty that would they warranty a LP? Maybe, maybe not. Anyway my trust factor is very low and I like to do my own wrenching so I know what is done is done right. Plus I wanted to put on the upgraded banjos. So it did cost me $150 but I had it done in an hour and didn't have to drop it off and pick it up and be at their mercy...<br><br>Anyone try one of the Carter P4601HP's? The plumbing swap looks easy and even benifical if you can eliminate two banjos. But how do you handle the jump from 1.4 to 4 amps and have it operate on the stock ECM power supply?

Copenhagenjunkie

[quote author=jec3 link=board=13;threadid=12587;start=0#121171 date=1048806046]<br><br>Anyone try one of the Carter P4601HP's? The plumbing swap looks easy and even benifical if you can eliminate two banjos. But how do you handle the jump from 1.4 to 4 amps and have it operate on the stock ECM power supply?<br>[/quote]<br><br>What do you mean?? I have bought pumps from NAPA and just put one on my dads truck truck from cummins- They had the same #'s stamped into them. I am running a 4601 HP that is how it is listed on the NAPA ticket. I have never had any problem with the larger apms.