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Old 05-18-2017, 08:36 PM   #1
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Join Date: Sep 2014
Location: Old Hickory, TN
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Year: 1989
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Chassis: All American FE
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Cummins 8.3 Bogs Down Under a Load

OK Friends...I about at my wits end here. I have a 1989 Bluebird All American FE with a 8.3 Cummins/4 spd Allison Automatic drivetrain with a 4/11 rear end that bogs down HARD when pulling a hill - never did that before. In fact the thing normally runs like a dream, and pulls hill at 70mph - no problem. The engine is strong, smooth, and purrs like a kitten at idol, revs up and down perfectly, does not blow bad smoke - at all. All pressures look right, all temps look right. It's just a bog bitch now, I'm stumped!!!!

Here's a list of things I have done in an attempt to remedy my problem.
1. Drained Diesel tank...YUK - NasTee, flushed out sludge.
2. Replaced ALL fuel/cooling/hydraulic/air filters I could find.
3. Replaced all fuel/hydraulic/cooling lines and clamps that looked the slightest compromised.
4. Flushed out cooling system.
5. Pulled the Turbo, it had some warping and blade damage, replaced it.
6. Pulled the fuel injector lines, blew them out, and pulled the injectors for inspection and cleaning.
7. I considered pulling the lift pump BUT when I did a fuel flow check the system gushes clean fuel.

Any ideas?? Short of taking it into a Bluebird dealership and getting ripped I'm out of ideas. I will most certainly and greatly appreciate any advice concerning what I may have overlooked.

Thanks Kids!!...Happy Day - Mark
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Old 05-18-2017, 08:48 PM   #2
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Have you tried injector cleaner? I know you said you pulled them. That is the last thing. Or injector timing. You seem to have covered everything else

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Old 05-18-2017, 09:02 PM   #3
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That made a very notable difference in my 5.9. Runs better, sounds better, smokes less.
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Old 05-18-2017, 09:03 PM   #4
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Join Date: Sep 2014
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Year: 1989
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In fact I will be cleaning the injectors out tomorrow. A local diesel repair/supply house here in Nashville offered to put them on their machine to clean out for $15 each. I'm gonna try that. The fuel lines have been blown own out and or replaced. Like I said...I'm STUMPED!

Thanks for the response.
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Old 05-18-2017, 09:12 PM   #5
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Get a gauge and check fuel pressure at the pump while pulling your hill. It sounds like you're running out of fuel. So short of actually checking it, everything else would be just a guess.
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Old 05-18-2017, 09:16 PM   #6
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Join Date: Sep 2014
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Are you thinking the lift pump, or the main injector pump??
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Old 05-18-2017, 11:20 PM   #7
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I strongly recommend having a good fuel pressure gauge on the output of the secondary filter - it will show the main pump's health. Between the primary and secondary filters I also have a Racor fuel filter restriction gauge that will show if the primary 5-micron filter is getting blocked.

Have you checked if there are any pinholes in the fuel suction tubes from the tank to the primary filter and from there to the pump? A tiny pinhole will introduce air into the fuel, but obviously won't leak fuel out.

John
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Old 05-18-2017, 11:31 PM   #8
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Do you have a boost gauge?

I started to ask if you could feel the torque converter unlocking, but realized you mentioned previously pulling hills at 70, which would mean there was no downshift involved and the converter stays locked. Are the hills big enough that the engine's lugging because the transmission should be downshifting and it isn't? Or is the engine just low on power?
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Old 05-18-2017, 11:34 PM   #9
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Join Date: Sep 2014
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Year: 1989
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Chassis: All American FE
Engine: Cummins 8.3
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Hi John...Thanks for the advice about the pressure gauge monitoring! I will most definitely check those things out. Incidentally, how to you spot pin holes that may be sucking air under a load if they don't leak "out"??

Thanks...Mark
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Old 05-18-2017, 11:38 PM   #10
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Join Date: Sep 2014
Location: Old Hickory, TN
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Year: 1989
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Chassis: All American FE
Engine: Cummins 8.3
Rated Cap: 84
This is a new issue. Pulling hills easily used to be the norm, now the engine bogs down and chokes out. It's not a shift problem, or a tranny problem. It is quite maddening though! I almost had to be towed home the other day...limped home.
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