the.hogman

OK boys, here we go...

Friday I replaced fuel filter that only had about 5,000 on it. Looked good but dark, no residues or any buildup of any kind. Canister was clean as a whistle. Took off pre-filter and replaced the screen. Only some small metal shavings but another thread indicated this is quite common. No other issues to be seen here.
Cracked the overflow and pumped the heck out of the lift pump. Got a couple of bubbles but no fuel spurts. Odd, I thought...
Cranked her over and she fired right up. Ran for about 2 minutes and died never to start again.
Cracked the overflow and pumped the primer. I thought it very unusual that it wasn't blasting fuel when I did this. Still no start.
Heck with it, needed it to run so I bought a Carter lift pump from the local parts store ($140) and installed it. Also bought enough diesel line to replace back to the tank, but wanted to try one part at a time.
Runs perfectly. Haven't replaced the supply line yet, but will anyway this coming weekend.
I had already tapped the banjo and put the needle valve in to monitor fuel pressures. Just didn't have a gauge yet... Clearly this would have been nice to have PRIOR to these issues.

Would a gauge have hit this problem on the head before it got to this point?

I will be driving her this week and I'll report back if the lift pump was indeed the problem.

patdaly

Yes it would have, though I am confused, I have always been told the P7100 will draw enough fuel to run even if the LP is bad.....

One thing is for sure, i am waiting anxiously for your report, perhaps we all can learn something here......

the.hogman

Reading my mind! Never would I have thought the the lift pump would leave me sitting dead from what I had been told. I always assumed I'd still be able to limp around. I'll put on a gauge and take a look at the old pump to see if there is anything tell-tale about it. Maybe it failed in such a way as to not let the P7100 draw through??

justme-

just a couple of related asides-
1 the low idle adjustment- you do not need an optical tach to set it. Both Cummins and Dodge use the in dash tach. The lowest line on the tach above 0 is 750 (confirmed by a Cummins tech with an optical). I had Cummins do it and show me when I first got my truck (benifit to living near them).

2- replace the supply lines. The lift pump doesn't need to fail and block fuel, the injector pump will draw fuel, just not well, but I suspect you'll find a leak in the fuel supply lines either the steel along the frame of the flex connecting the steel to from the frame to the engine itself. Foster's sells a kit, but all you need is the proper soft line to replace the flex. I always keep a short section of soft and a couple of clamps because the same exact thing happened to me (same symptoms) when my steel line developed a leak.

I replaced with factory hard lines, but having SS ones made up next time.

the.hogman

Thanks for the note. I have adjusted the idle speed some time ago and it continues to be dead on. Clearly I was having some sort of fuel issue.

I find it interesting that you indicate I could be sucking air form the supply line and hence not drawing through the lift pump by the P7100. That is a great point! I hadn't looked at it that way.

It still means I seem to have identified that my lift pumop was on its way out, but that might explain why it wouldn't suck through and continue to run.

As I stated above, I will be replacing the supply line and probably the return while I am at it.

So far, it seems I am up and running.

When I replace the lines, I will report back if I see anything. I may try to pressurize them once bypassed and see if there is an obvious air leak. I will mention that all of the lines are completely dry of fuel stains so it must be a pretty small leak to let air and not fuel go through.

infidel

With an air leak it will almost always be hard to start. The IP will suck fuel enough to run the engine poorly but just a little air and it will airlock and not reprime itself.
Both the factory service manual and a TSB say not to trust the dash tach.
My experience is they are right, the dash doesn't read correctly at low rpms.
I've found adjusting the idle by ear to be plenty good enough.

illEatUrDuramax

I agree, I have always adjusted by ear too. Even with friends trucks. Works just fine.

justme-

I know the FSM's both say use an optical, but my tach (up until I just replaced the ESS) was spot on at 750- gotta check it now with the new ess, and they told me that's how they did it- dash tach.

I figured supply lines because I had pretty close to the same symptoms when mine was leaking- hard start, terrible idle, stalling @idle...