Engine/Transmission (1994 - 1998) unsolved mystery

[MFerraro]

Truck: 1995 Dodge 3500 cab-chassis 4wd standard trans. 162,000 miles Only changes TST #8 torque plate, 3" straight exhaust, no cat, no muffler.
I purchased the truck from the original owner. It had a very good service history. The truck was well taken care of.
I have had the truck for 3 years and put only 20,000 miles on it.
The problem is very intermittent. In the past 3 yrs the problem has only occurred 5 or 6 times. The problem starts and stops without warning. I have
addressed what I felt were all the obvious possible issues. Otherwise the truck runs exceptionally well. I have made the rounds locally but no-one seems to have
an answer. The problem can begin at start up or when running down the road. The only way I have ever been able to make the problem go away is by shutting
the truck off, waiting 5-10 minutes, and restarting. This is not a guarantee that the problem will stop, it is just the only way it has in the past. I have tried keeping the truck running
until the problem goes away, but have never been able to accomplish this.
The problem. It can occur at start-up. Only ever when warm. The engine will crank excessively but will finally start. It can also occur when running down the road.
You will hear a change in the exhaust and the truck will start to run rough. If you stop the truck, it will not idle, it will stall. If you attempt to run through the gears,
when you let up on the throttle and depress the clutch the engine will continue to rev up. You must let off of the throttle and wait until you feel the engine slow
down then go ahead and shift gears. The truck will then stumble badly and just about stall before it picks up again. When all this is taking place you can feel a change in the pressure of the throttle pedal. The back pressure on the pedal drops dramatically. The exhaust temp will not go to normal temp, and the boost will also be low. If you attempt heavy acceleration you will not get any smoke, where normally I would get a small plum for a few seconds.
Sometimes, the engine will idle but lope up and down slightly. When it does I can hear a load clicking or tapping sound that seems to be coming from the injection pump.
When it will idle, if you blip the throttle even the slightest bit and let go, the engine will rev slightly and stall.
I am not a diesel guru, but it sure seems like some type of fuel issue.
The truck has never left me stranded, I have always been able to limp it home. I let it sit until I need it again, and everything is fine. It may be many months until the
problem shows up again.
This is starting to really bug me and I would like to find out what the problem is and fix it before I do get stranded. This seems to be the place for answers, so I am hoping for the best.
Thanks,
Mike

 

[fest3er]

On first guess, I say it sure sounds like your governor springs are out of whack.

But it could also be the go-pedal linkage shaft on the p-pump (lower rear). Mine became corroded over time and hung up when warm; PB Blaster, manual operation, and lots of pucka-puckas of oil loosened mine; it's been OK for a few years now.

 

[GAmes]

The next time it happens pour some cold water over the injection pump. If the problem goes away you have a sticking plunger, and need to get the IP repaired.

 

[MFerraro]

GAmes, I will try your idea for sure. If it solves the problem, is rebuild/repair the only option? Do you think the plunger is sticking because it is worn or because it is dirty? Or both.
If it does not solve the problem, what would you suggest?
Thanks, Mike

 

[Vaughn MacKenzie]

Sounds like the shutdown solenoid to me. It's what turns the fuel on to the pump to let the truck run, but if the linkage gets dirty or starts binding, or if the relay starts getting weak it can potentially cause the problems you describe.

It's mounted to the side of the injection pump kinda toward the back. With the key on it should be in the Up position and locked into place. If it doesn't stay securely locked in place if you try pulling down on it by hand it's time to do some maintenance, and replace the relays that are up above the brake booster area at the back of the engine bay.

Pic of the shutdown solenoid #ad

Pic of engine diagram to locate it #ad

 

[GAmes]

If it is a sticking plunger rebuild/replace is the only option. It is a common problem with '94s and '95s. If the problem only pops up when the engine is at operating temp I know of no other cure.

 

[MFerraro]

Thanks to all for reading/responding to my post. As to the suggestions regarding the solenoid and linkage, as I mentioned in the original post I checked what I felt were possible obvious causes of the problem. I subscribe to the magazine, and read the forums. These were some of the first things I looked at. I feel very sure in saying it is not one of those issues.
GAmes, I hate to say this, but I am hoping the truck acts up again soon so I can try your suggestion. In the meantime I am going to continue to nose around locally and see if I can get someone to confirm your theory. I feel you could very well be on the right track as I have been unable to find anything on the truck that indicates otherwise.
Thanks again,
Mike

 

[MLee]

Was the Mods already done? or did you do them your self. As mentioned what about the governor springs, have they been tampered with? If so they are very touchy to adjustment. How about the overflow valve? Just more suggestions

 

[MFerraro]

GAmes,
As luck would have it I got hooked up with what seems to be a good local shop. I talked with them and they also feel I have a sticking plunger problem. They showed me a pump they had apart and went through everything with me. They feel that one or more of my plungers is sticking when the rack (throttle) asks it to rotate and change the fuel delivery amount. After seeing how the pump works and talking with them, this seems to account for the strange things that occur. They offered me some additive that they feel may help the problem, but said that rebuild was the only true solution. Based on what you offered and my discussion with them I think I have found the cause of the problem. I am going to try the additive and see what develops.
Thanks again for your input.

 

[surfbeetle]

Please post your findings once you have had a chance to try the additive. With only 160,000, even thought it's an almost 20 year old truck, that seems a bit too soon to need a rebuild in terms of mileage. I have 225,000 and it's still running strong. My only adventure into the IP was to add the #5 plate. I want to see how this plays out for if and when it happens to mine.

 

[MFerraro]

I will gladly post any new developments. The magazine and forum have made a lot of useful information available to me that I would probably not have discovered otherwise. I was already using an additive that I was purchasing from Geno's Garage. The Racor additive. But It was not listed in the last catalog that I got. I began using the Racor after the first couple times the problem occurred.
It had been quite a long time since the last time it cropped up so I thought it had taken care of the issue. They gave me an additive called Stanadyne.
I agree, the mileage seems low to be needing a pump rebuild, and I am basing this solely on what I have read and been told about these engines.

 

[surfbeetle]

Stanadyne makes additives as well as injection pumps, they were who GM used to supply the pumps on the 6.5 Diesels. Like Bosch, their mechanical pumps were good but their first foray into electronically controlled pumps were not so good. Hopefully their elixir will be just what the doctor ordered.

 

[MFerraro]

Well, for all of you who have been following this I have an update. I have been using the Stanadyne additive in place of the Racor. I am sorry to report, the Stanadyne did not solve the problem.
The truck acted up again. However, I did try The idea GAmes suggested. I poured 1 gallon of cold water on the pump while the engine was hot. Upon restart, all was good. No offence GAmes, but I am still a bit skeptical about your remedy. I have refilled the jug, and will try to repeat the scenario. If this cures the problem again, I will be pretty convinced. I have inquired as to the cost of having
the pump rebuilt and found it is a bit pricey. I am a bit unsure about spending $1000+ on the pump at this point. I will continue to run the truck for now. Will post any new developments.

 

[GAmes]

No offence GAmes, but I am still a bit skeptical about your remedy.

No offence taken. It is a phenomenon I read about on another forum, not something I have experienced. However, there have been several people on that forum who verified it, so I threw it out. As for mileage, the person who first suggested the test had his '94 p-pump replaced under warranty, so less than 100k.

 

[GAmes]

I remembered that the person who reported the IP problem used to be a TDR member, so I put his name (illflem) in search along with injector pump as the key words. Guess what popped up. https://www.turbodieselregister.com...on-or-lift-pump/page2?highlight=injector+pump

 

[MFerraro]

GAmes, I read the link you listed. Boy, that story sure sounds familiar!! I have a full jug of H2o behind the seat to try again. Interesting talk in the thread about the shut-off
solenoid jumping up & down. I noticed before I poured the water on the pump, that the solenoid coil was pretty hot. I tried pulling down on it, but it seemed fine. I know it is a holding coil, but it still seemed a bit warm to me. I may remove & replace with a cable, just to see what happens.
Thanks for the help.

 

[MFerraro]

Here is another update. The problem resurfaced again. I poured my water on the pump again. This time only 1/2 gallon. Lo and behold GAmes, it worked again. I proceeded on to my destination.
The problem reoccurred about 30 miles later. I was close to where I was going so I limped the rest of the way. The truck sat for about 4 hrs. and was fine for the trip home. Has been running fine
since. I did notice something else tho. While the truck was running poorly, there was a noticeable drop in voltage according to the volt meter in the dash.
GAmes, I did take time to read the post you listed. The story sounds hauntingly familiar. Thanks.

 

[GAmes]

There is no telling how long the water trick will work. As I'm sure you know, Murphy's Law dictates that failure will be far from home at the worst possible time. If it was my truck I would have a new p-pump incoming. The voltage thing is more than likely the low/intermittent rpm.

 

[MFerraro]

GAmes, I am sure you are correct in saying it will completely fail at the worst possible time. I have to tell you tho, I am a huge believer in not messing with something until needed.
I am just having a bit of trouble accepting that the pump on this truck needs rebuilt already. (163,000). As far as the voltage goes, I believe the voltage would only drop if the rpm
became to low. I don't think the rough running of the truck would cause a voltage drop at 1500-1800 rpm. I am not even sure there is a connection between the two. I will pay closer
attention next time to see if it happens again. The water jug is full again & I will proceed forward for now.
Thanks much for your input.

 

[GAmes]

The connection is the engine speed sensor that tells the PCM if the engine is running. The PCM controls voltage. As for mileage, at least one failed with the truck still in warranty that I know of, so I'm sure there are more. Good luck. With summer upon us I'm sure you will have it happen again.