Stumbling 1st Gen

[TerranceB]

My '93 has developed an intermittent stumbling problem.
I believe it is related to engine temperature since it most often occurs after driving a few miles OR when I plug the truck in overnight (which I do if the temp fall to 50 or less), and it occurs ONLY when I pull up to a stop.
This has been going on for a few months now and yesterday I found a coolant leak from the rear corner of the head at the #6 cylinder. I was wondering why I've had to keep adding coolant for the last year or so with no noticeable loss of power at speed.

I know I need to find a mechanic to fix this but...could this be the cause of my stumble?
I do not trust my local dealership to accomplish the repairs so I'll need to find a Cummins Certified Mechanic near me to do the work.
Other than regular maintenance I only allow a Certified Cummins mechanic to touch the engine.
Can anyone suggest one in the Mt. Vernon, WA area?

Note: This is the 1st major problem I've had on my truck since I bought it new in '93.
235k miles and everything on the engine is original.
The transmission, TC, and Flex-Plate were replaced 3 years ago but that's it...everything else is factory original!

 

[Philip]

Welcome to the forum.

I live in Indiana so I can't help on a mechanic in that region.

One item I would suggest you look at. The power wire to the injection pump on our trucks has been known to loosen up the terminal from years of vibration. Check that terminal it might cause the stumbling problem.

 

[TerranceB]

Welcome to the forum.

I live in Indiana so I can't help on a mechanic in that region.

One item I would suggest you look at. The power wire to the injection pump on our trucks has been known to loosen up the terminal from years of vibration. Check that terminal it might cause the stumbling problem.

Thanks, I'll check tht out today!

Hmmm....I wonder why my local dealership didn't think of something simple like that?
Although when I talked to him he did mention that their diesel technician was only schooled on the newer (read that as computer-controlled) Cummins diesels. He wasn't even schooled on the Jeep dieselsthey sell!!!
Hence the reason I'm looking for a mechanic...

Thanks again for your input!
T

 

[JLEONARD]

I would also check the lift pump. I had a new one (less than 10 K miles on it) fail and it acted a little like that before it went completely. The rubber diaphrams inside disintegrated and eventually ddi not seal when they should have.

 

[TerranceB]

I'll get it checked again.
I was told there was nothing wrong with it only 2 weeks ago.
But they could've been wrong.

 

[DVolk]

For a shop , I'd call Cummins NW , or if there is a case tractor dealer near you you might talk them or there mechanics as there the same engines , on your sputtering I'd check your fuel filter and and a bottel of injector cleaner and anti gel sounds like you might have a slug of water in your fuel and possible sticky injectors , of which Cummins can clean they have a box the hook to your fuel system that cleans the system out

 

[TerranceB]

Thank you DVolt...

I have done all of the things you mentioned more thn once in fact.
The problem continues and it is still intermittant. I find no ryhm or reason for when it will occurr next.
Maybe my truck picked up a mischievous ghost somewhere...

...and Cummins NW is next on my list to call.

Thanks,
T.

 

[mweiman]

Can you describe the stumble a little better? Does it die completely ever, just cut out and come right back, miss at all? Does the engine possibly pull down like the torque converter is locked up?

 

[TerranceB]

Occasionally when I come to a stop the engine will try to die.
It doesn't die though....it stumbles until I add just a SLIGHT TOUCH of throttle.
Then...as long as I maintain that pressure it's fine.
The stumble only occurs at idle.
I notice no difference in performance or mpg going down the road.

I've never experienced a TC problem so I can't speak to that as a comparison...but it might be similar (or be the cause, even though the transmission and TC are only 3 years old).

And then there's that head gasket leakon the #6 cylinder...

Wish I could give you more to go on...

 

[DVolk]

I wonder if you don't have the " O " rings going bad on your plastic fuel supply lines from the tank I replaced mine as the prime would back off , now it fires like it should also your lift pump might. On its last legs

 

[TerranceB]

I wonder if you don't have the " O " rings going bad on your plastic fuel supply lines from the tank I replaced mine as the prime would back off , now it fires like it should also your lift pump might. On its last legs

How would i test the lift pump and are the O-rings replaceable or do i need to replace the ines too?

 

[DVolk]

You could try a pressure guage for the lift pump but for $45 I'd swap it out , the O rings I've heard are changle able by replacing the ends ,what I did is bought a few feet of diesel grade rubber line and 1 fitting for the lift pump and cut the connection off and slid the hose over the plastic line and double clamped on the hose and single on the pump and return line ,I did not do the rear yet the front move alot , I also slid the fuel line goi g to the lift pump in a bigger hose for protection it is 3/8" and 5/16"