Engine Stumbles

[Fogie]

My brothers 1st Gen. 93 CTD. Been thru the wiring and cleaned all the connections... great improvement, but now when he lets off the accelerator, or just tries to hold it steady it starts missing. A friend has suggested the injector pump, but I lean toward the lift pump. Truck has about 190K on it. Injector pump was replaced about 100K ago. Never changed the lift pump. Any other ideas???????



Thanks



Terry

 

[Steve Graham]

Rather than repeat my self I'll post the link to my problem and the soluation. The problem you describe sounds like what I had.



https://www.turbodieselregistry.com/forums/showthread.php?t=129718

Hope this helps.

Steve

 

[Fogie]

Thanks for the reply Steve. At idle it will die. Most of the stumbling occurs when he lets of the accelerator. I still think lift pump.

 

[BushWakr - RIP]

I'm assuming you have a decent idle setting right... ??? ... . you should have an idle of 800'ish with the AC on max and the trans in "D" if auto equipped.



No tach... no problem... . keep raising the idle till the drivers mirror stops wobbling. . and then go another 1/2 to 1 full turn. That will take you real close to the 800-825 mark.



pb.

 

[Fogie]

Found the problem... thanks for helping. Seems the idle roller inside the injector pump has a flat spot which in the end sends a bad code to the computer causing the problem with stumble and dying. 900 exchange and I get to figure out how to change the pump.

 

[MMiller]

sends a bad code to the computer

Uhhmmmm, my first gen has no computer that controls the injection pump in any way. What computer are you talking about????



If there is a small problem in the pump, why not just get it fixed instead of a different pump?



Michael

 

[BushWakr - RIP]

Fogie... . I "think" you may be having some "voodoo" done on ya... .

If you look at that pump you'll see connections on it and NONE are used as control by the PCM on these trucks.

The only functions that even remotely relate to the PCM is the tps, the start/stop solenoid, ksb function... that's it... and even those are just "sorta" in the circuit so to speak.



Maybe check back with the pump shop and get them to "re-explain" it to you cause there is some bad communication in there somewere bud...



bob.



edit: in the case of bad communication, no problem but if they don't know this then you need to decide if you want to deal there... .

next if the pump has internal issue's it's almost as costly to have your pump repaired (labour) as it is to get a good reman unit. If there is damage to the cam/roller ring then it is time to go thru the pump top to bottom.

 

[Fogie]

I finally got to talk at length with my brother and a couple of mechanics that he has had look at this problem. The problem is intermittent and at idle only. It will all of a sudden drop below 700 rpm and then die. Discussing this problem I have learned there is a small roller deep inside the pump that controls the idle has developed a flat spot on it. (There was been an update a few years ago that remedies this problem. ) When the rpm drops below 700 the pcm shuts down the engine. To replace the roller is from $12 to $1500 to rebuild the pump. I can get a reman with the update for $900. Now I guess it's reading time so I can learn the particulars about changing the pump. If there are any other ideas, jump in and let me know.

 

[Paychk]

On the early Cummins the PCM has no control over the engine, it controls the alternator, cruise control, overdrive on the auto trans and A/C. If the engine is dying it is because of a lack of fuel ie the fuel solenoid closing prematurely, clogged fuel filter, weak lift pump or internal problems in the injector pump. I would be sure of the first three items before pulling the pump.

 

[1stgen4evr]

Get them to show you the part that is in question and mention that you will want to have the old one as a desk ornament. And post a picture of the item. I think quite a few folks would be interested in just what the problem is, if it is indeed a flat roller.



I would look elsewhere extensively before pulling the pump.



James

 

[Chris and Sam]

what about it having an air leak in the fuel system?

 

[bgilbert]

I have learned there is a small roller deep inside the pump that controls the idle has developed a flat spot on it. (There was been an update a few years ago that remedies this problem. ) When the rpm drops below 700 the pcm shuts down the engine.

:-laf Sounds like someone has been feeding you some good . . Survey says: (insert family fued X soundbite)XXX. Where are they getting this info that the pcm shuts down the engine :-laf ?

 

[Fogie]

Run the gambit. Started with the fuel filter, then the lift pump, then the fuel solenoid. Doing these one at a time did not make any difference. What did make a difference was increasing the idle speed. Raised the idle 100 rpm and no longer have the problem. Been running fine now for a couple days without dying or stumbling at idle. If the problem returns, then we will look at the IP. Thanks for all of your responses.