'96 2nd gen 3500 (re-posted from DTR)

Truck has been hard-starting for a couple months now, after about 8hrs of sitting it starts as if there is air in the lines. The longer it sits without running the worse it gets. If I haven't driven the truck in a week I know I'm in for a helluva time getting it running...but once it chokes though all the air it purrs like the day it was born.

I had figured the lift pump check-valve was failing so I bought a new pump a few weeks ago and just haven't had the time to swap it out. Yesterday evening I went to warm the truck up and after about 3 minutes of idling the motor died out and it WILL NOT start now.

I'm about to tackle the lift pump but I'm not so sure it isn't a faulty return line from the injection pump or tank->lift line. Been conceptualizing with Joe G's writeup ( http://www.cumminsforum.com/forum/94...m-writeup.html ) but I'm less sure of the culprit now than before. Cleaned and re-sealed the pre-filter a few weeks ago, shouldn't be an issue there. I also haven't ruled out bad gas.

I need to have this thing running by Monday morning, I will be infinitely grateful for any and all advice you guys could offer that'd help me narrow it down.

11/12/2011 12:39:48 PM

Also, could be the injection pump overflow valve, apparently if this is faulty it'll create white smoke which I do see during those hard starts. And Jeepman suggested I consider the fuel solenoid and relay

this would be so much easier if my bike wasn't in the shop and I could actually go pick up parts...right now I'm stuck at the house with whatever I have in my garage and a truck that I can't even get up on ramps

[Edited on November 12, 2011 at 1:48 PM. Reason : sadf]

11/12/2011 1:35:19 PM

pull that ugly mexican body kit off it and you can probably get under there without ramps

11/12/2011 2:15:48 PM

hahaha i was JUST thinking that

did everything i could from the top end and then tried to get under it to pull the starter and swap the lift pump...apparently I'm just too much man for them ground effects


so anyway -- replaced the fuel filter, primed it, and cracked the first three injectors. turned it over for a while and didn't even see any fuel coming out of the injector lines

11/12/2011 4:00:42 PM

You dont have a fuel pressure guage on it? Brave man.

11/13/2011 12:24:12 AM

Dave, you need me to bring my ramps and pull the truck up on them with my Accord. It'll do it...I pulled a Chevy C20 up on a trailer last weekend. Yeah, I'm crazy like that.

Joel...a fuel pressure gauge would be nice, but there's no bravado in not having one on a P7100 injected engine with the piston style mechanical lift pump. Your VP44, however, will shit the bed in short order if not supplied with adequate fuel from whatever electric lift pump you run...and you already know all that.

[Edited on November 13, 2011 at 6:29 AM. Reason : Blah blah blah]

11/13/2011 6:16:33 AM

Yeah I forget he has a 12v.

11/13/2011 9:48:43 AM

Hahaha holy shit Dan that's great. unfortunately as it sits it'd need a push onto the ramps. ..unless you've got block and tackle and a wayto anchor it without voiding my deposit

I'm gonna go check the fuel solenoid and relay here in a bit, if that doesn't work I'll give you a call

11/13/2011 1:50:22 PM

yep, fuel solenoid relay. just gotta lift the plunger manually until I can pick up a new relay. Probably means I need to replace the starter contacts too

good call jeepman

11/14/2011 2:31:28 AM

...y'aint shit without









j/k.

11/14/2011 7:59:37 AM

Yeah that's actually on my list of shit to do before the turrists blow up a nuke in the sky

[Edited on November 14, 2011 at 9:40 AM. Reason : impressively clean installation on the interior though...might pick your brain when I jump on that]

11/14/2011 9:39:07 AM

haha that's not my truck, btw.

11/14/2011 10:35:51 AM

NEW PROBLEM

Started it up tonight and it did the same thing -- idled for a few minutes then died a hard death. will not start now. lifting the solenoid does nothing anymore. bleeding the water separator, priming the system, and cracking the injectors all didn't help. in fact, didn't see any fuel bubbling from the injectors but once in a while it'll catch for a few seconds and try its damndest to start but just never does. there is plenty of fuel in the tank

i'm at a loss. now i'm in an even bigger time crunch at a house way out in the sticks (precisely the middle of nowhere). it's cold out here, ~34 and dropping, but I don't see why that'd be an issue. I thought maybe somehow a whole lot of water condensed in the tank because usually it'd catch for just a little bit after each time I bled a little off the fuel filter/separator, but I really don't know

my truck is sick y'all. urgent -- need to get this thing running before noon. any advice?

11/25/2011 12:34:30 AM

Gonna copy my correspondence with someone on DTR --

Quote :

"Have you changed that lift pump yet? Now would be a good time to check fuel pressure. Sounds like that's your culprit - if you can prime it up with the primer and it catches but won't run, it's likely the lift pump is toast. The primer is it's own pump so it can still work when the lift pump itself doesn't.... That is..... if you haven't replaced the pump already."

Quote :

"I haven't replaced the pump yet. If the lift pump is shot but I can get it running the IP is enough to pull fuel while it's running, no? Unfortunately I'm stuck out here with no spare parts and only the tools I keep in my toolbox. I REALLY don't want to go the ether route but if I were to give it a shot, what is the safest way to go about that? It was a long haul to get where I am so I suppose it's possible that the pump failed completely somewhere along the way and the IP kept it running until I got here and killed the motor"

Quote :

"I don't think the p-pump has an internal charge pump so I don't think it would stay running without the lift pump working at some capacity. I'm not 100% sure on that though. Seems like maybe the lift pump failed enough that it doesn't pump enough fuel to start, but once the rpm's are up, it has just enough to keep it running. I wonder if you crimped off the return line and got someone to turn the key while you pumped the primer like mad and see if it would run then? If it did, that would pin-point the problem I'm thinkin'.... If it works, don't run it too long with the return crimped off."

Quote :

"I don't have another set of hands at the moment, I'll try that in a little while when someone else will be around...In the meantime I've got the heater plugged in and I'm gonna try to get the thing pointed downhill to help matters. If it won't start then I'm gonna pull the overflow valve off and check the spring inside."

11/25/2011 11:56:09 AM

got it pointed downhill with a tractor and pulled the overflow valve off, the spring was a little short. stretched it out to just over .5" but still nothing.






come on guys i have a match tonight

11/25/2011 1:16:07 PM

I pressurized the tank with an air compressor and still nothing. I am getting fuel at the overflow valve when I pressurize the tank, so at least I know fuel is getting to the injection pump. From there though it's not making it to the injectors. I make sure each time I crank it that the solenoid is opened, but maybe it's falling somehow when I start cranking? What say ye?

11/25/2011 2:15:46 PM

D'oh. Pressurizing the tank will just make fuel flow back up the return line which is why I saw fuel then. I cracked the OFV and cranked it, nothing come out. Shut it off and manually primed it and got fuel bubbling out. Guess that means my lift pump is completely shot. Gonna have to leave it here and get back to raleigh, get my tools and parts, and come back.

[Edited on November 25, 2011 at 3:36 PM. Reason : fucking thing]

11/25/2011 3:34:49 PM

I believe you can get a Holley pump at any advance auto that would be enough to get you home. In fact, I may have one here...

BTW I think my lift pump might only work intermittently but my carter aux pump on the frame rail always works as backup

11/25/2011 5:00:26 PM

have you at least checked to make sure you're getting spark?

11/25/2011 5:57:05 PM

fwiw, holley pump(s) can't supply the necessary pressure to effectively feed the P-pump (probably not the case for the 24v's).

I know most of this is a repost, but here's my methodology.... I've been stuck roadside a handful of times before


-pull fuel line from lift pump and blow it out/make sure it's clear
- make sure fuel filter is new/clean
- obtain water remover, if it makes you feel better double the dose, and add quart of 2-stroke premix oil for good measure.
- loosen 10mm head bolt from banjo bolt on top of filter housing and prime the lift pump manualy until fuel is bleeding from the bolt profusely.
- make sure fuel line from lift pump to injection pump is clear
- try cranking the truck... hold the pedal to the floor if it starts to fire. if it wont stay running... try some more. (i like to hold the starter down for a good 10-15 sec intervals just to be sure the fucker is going to fire and stay going)
- if after 3 tries of the above, have someone crack each injector line (at the injector), bleed, and close the nut once the truck is running fine.


I'm confident that if you have had the truck running for any amount of time, the lift pump isnt completely dead.... once you got the truck running does it lack performance?

Also, get some good, fresh fuel and top the tank off

11/25/2011 7:18:09 PM

Quote :

"underPSI irons man 13717 Posts user info edit post have you at least checked to make sure you're getting spark? 11/25/2011 5:57:05 PM "

This

11/25/2011 10:31:44 PM

Quote :

"fwiw, holley pump(s) can't supply the necessary pressure to effectively feed the P-pump (probably not the case for the 24v's)."

Guess you better carry some comfortable shoes then boys

11/25/2011 10:33:50 PM

updates?

11/26/2011 1:21:31 PM

Quote :

"I believe you can get a Holley pump at any advance auto that would be enough to get you home. In fact, I may have one here..."

Yeah that wasn't an option out there in the sticks. Besides, I already have a new OEM lift pump back at my garage

Quote :

"-pull fuel line from lift pump and blow it out/make sure it's clear - make sure fuel filter is new/clean - obtain water remover, if it makes you feel better double the dose, and add quart of 2-stroke premix oil for good measure. - loosen 10mm head bolt from banjo bolt on top of filter housing and prime the lift pump manualy until fuel is bleeding from the bolt profusely. - make sure fuel line from lift pump to injection pump is clear - try cranking the truck... hold the pedal to the floor if it starts to fire. if it wont stay running... try some more. (i like to hold the starter down for a good 10-15 sec intervals just to be sure the fucker is going to fire and stay going) - if after 3 tries of the above, have someone crack each injector line (at the injector), bleed, and close the nut once the truck is running fine. I'm confident that if you have had the truck running for any amount of time, the lift pump isnt completely dead.... once you got the truck running does it lack performance? Also, get some good, fresh fuel and top the tank off"

I will give your method a shot when I get back out there in a week or two (had to leave it where it was for the time being), sounds promising. Fuel filter is brand new. Since I have the new lift pump I'm gonna swap it just to make sure. Gonna bypass the pre-heater to make sure it's not sucking air and replace fuel lines pretty much everywhere. Gonna get a new OFV because when I pulled it out and apart the spring was definitely too short. I stretched it out but it's just a matter of time before it causes me more problems. Probably going to get a new solenoid relay and starter contacts (since I'm gonna pull that anyway to get to the LP).

I do feel like the truck has been a little sluggish of late. When I first bought it the thing ripped but lately it seems as if it's just been limping a little bit. I really need to get a damn fuel pressure gauge in there but given my other issues I really feel like it's just suffering from a lack of tank-side fuel pressure.

Quote :

"have you at least checked to make sure you're getting spark?"

damn you know I looked right over that

11/26/2011 2:05:50 PM

so who wants to buy me a fass or airdog


I'll show you my gf's tits

[Edited on November 29, 2011 at 8:16 PM. Reason : they're awesome]

[Edited on November 29, 2011 at 8:16 PM. Reason : the tits, that is]

11/29/2011 8:16:20 PM

....what's wrong with the stock replacement lift pump?




(and obligatory that's what they make credit cards .)

[Edited on November 30, 2011 at 7:22 AM. Reason : -]

11/30/2011 7:22:34 AM

Quote :

"....what's wrong with the stock replacement lift pump?"

11/30/2011 12:07:28 PM

derail:

...gotta love having my fuel cell outlet at or above inlet to lift pump, and 1/2" unobstructed line from cell directly to lift pump inlet

11/30/2011 1:10:20 PM

yeah thats beautiful when there are no air leaks


and nothing is wrong with the oem pump, I'm just wishing


also, wtf is the point of the fuel pre-heater when theres at least a quart of cold fuel between that and the IP at startup? definitely nixing that when I get up under there next week. got all new lines, ofv, and more coming

[Edited on November 30, 2011 at 6:43 PM. Reason : asdf]

11/30/2011 6:38:40 PM

packaging, i guess. fwiw the inlet barb on the lift pump is 1/2" male barb x 3/4" NPT iirc

12/1/2011 7:36:19 AM

So the lift pump brings fuel from the tank to the mechanical injector pump right?

12/1/2011 8:09:41 AM

^yes. the P7100 injection pump likes to have a decent inlet pressure in performance situations - like a constant 45psi. maybe not the case for paerabol's situation... but in general a good, constant pressure is ideal. as you know when rpms rise the pressure drop is lower - so the supply pressure can drop to 5-10psi in stock form... which causes poor WOT fueling, etc. Once you up the maximum fueling rpms the supply pressure becomes even more important (fill-time in the barrels based on the injection pump cam profile and the actual time duration available for the fluid to flow)

EDIT: also, the P7100 is backpressure regulated, so there is an 'overflow valve' on the return outlet of the pump that regulates the pressure internally to the pump case. over time the OFV can lose it's spring tension and become weak... usually causing the low pressure problems. In the case of my truck I have an external FPR and a gutted OFV (factory isnt adjustable). SInce the time I've obtained my regulator, a company has come out with an adjustable OFV valve, which appears to be performing well in the market.



hope that's not confusing... I'm not a guru or anything

[Edited on December 1, 2011 at 9:03 AM. Reason : -]

[Edited on December 1, 2011 at 9:05 AM. Reason : SELF PROCLAIMED NOVICE]

12/1/2011 9:00:25 AM

what's the big ass injector pump all the cummins guys switch to for crazy power?

12/1/2011 9:08:54 AM

??? the p7100 is the go-to for mechanical injection... can be had in built 12mm (stock) and 13mm plunger variants. (like 1200hp or so)

maybe thinking of the Sigma, 16mm plungers... like $10k-ish (1500+hp)

and of course there are custom pumps etc that can TAKE IT TO A NEW LEVEL. Scheid Diesel runs a 12cyl bosch pump and feeds each injector twice:




[Edited on December 1, 2011 at 9:19 AM. Reason : see now ive derailed the thread and am all excited talking about this shit ]

12/1/2011 9:15:13 AM

I'm learning but i'll bump extravaganza

12/1/2011 9:25:20 AM

haha word.


didnt want to shit on paerabolzzzz paradezzzz

12/1/2011 9:37:05 AM

naw man no worries that shit gives me a hard on

12/1/2011 10:00:15 AM

WE'RE ALL HARD.

im going to drive mine after lunch!!!!

12/1/2011 10:03:22 AM

headed back out there tomorrow evening, gonna get crackin' on it bright and early on Tuesday. Got a replacement OEM LP and a box o' parts, gotta have it running.

I want to pick up some 8mm x 30mm x 1.25 pitch studs with nuts to replace the stock bolts, supposedly makes the job much easier. That something most hardware shops are gonna have in stock?

12/12/2011 1:51:58 AM

come fix mine while you are at it! either have a boost leak or I've fuckered up my afc housing after fiddling with it the other day...no boostey/fuel after 20-30psi

12/12/2011 9:20:16 AM

do you know if the defueling issue is a function of boost pressure and not RPM (directly)?

[Edited on December 12, 2011 at 9:59 AM. Reason : phone]

12/12/2011 9:58:55 AM

on the p7100? limiting total fuel at WOT controlling max engine speed or the transient response when you floor it?

12/12/2011 10:18:29 AM

I was asking about yours, out of curiosity

12/12/2011 10:23:04 AM

oh, my main assumption is it's afc related from one of two items:

I've either got a boost leak causing the afc to not travel appropriately

or

something is bound up where i arranged spring/washer/etc. on the afc shaft, again causing to not travel appropriately.


(i checked fuel system, added new filter the other night, and tightened up my fuel pressure regulator so that's off the list. it will also free-rev to 4000 with no boost, so im also couting out gov springs)




or it could be something entirely new that i've got to fix again, damnit

[Edited on December 12, 2011 at 10:28 AM. Reason : -]

12/12/2011 10:27:00 AM

yeah but just imagine if you'd left everything stock.. you'd never have any fun getting to fix the shit that broke

12/12/2011 10:29:43 AM

oh, yeah... that's a given.

12/12/2011 10:33:56 AM

ajhfapoiwefusldfmns,dmfs.dmfnsad.,fsdpdofuwepowe

Replaced the OFV and removed the preheater, and now I can't get the damned LP outlet line unscrewed from the pump. Spent ALL DAY on one fucking nut. Used WD40, PB blaster, double wrenched it, damn thing's about to completely round off before it releases. Tried removing the banjo fitting on the other side of the outlet line at the filter inlet, but that's a no-go too. Not enough space to pull it out...

wasted a whole fucking day on one nut. What a stupid thing to hold up progress. any ideas?

12/13/2011 7:23:05 PM

is it a reverse threaded bolt? are you turning it the right way?

http://dodgeram.org/tech/dsl/fuelpump/replace.htm

[Edited on December 13, 2011 at 7:41 PM. Reason : maybe this helps?]

12/13/2011 7:38:28 PM

many thanks, but I've read that one...and no it's not reverse threaded. I even double-checked on the oem replacement I have, it's standard thread

[Edited on December 13, 2011 at 8:29 PM. Reason : asdf]

12/13/2011 8:28:42 PM

Those things are really hard to break loose, I had a helluva time unscrewing the inlet elbow/barb fitting when working with mine.

12/14/2011 7:19:39 AM