Dodge Cummins Diesel Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
Hey all,

The Back Story:
I have lurked here and the other diesel forums for the last couple years. I have a 94 auto 4x4 with 190K mi. When I bought it I'd never driven one (so I had no frame of reference) and it was the only one for sale in the area (rural virginia). I was under the impression the truck was stock except for the air filter (K&N) and the exhaust (5" straight pipe). As soon as I purchased it I installed gauges (EGT, Boost, Trans temp), tabbed the kdp, and to appease the neighbors, stuck a 4" turbo back with a generic muffler on it. About 2 weeks into my purchase the transmission gave up. I knew it was a risk when I bought it, but didn't think it would give up so soon. I talked to Goerend Bros, and went with their standard build to replace the unit in the truck. At the time I didn't imagine I'd ever try to tow more than 10,000 pounds. Since then the truck has been reliable, but produced pretty lackluster fuel mileage (10mpg towing 7k pounds 8-9 towing 10-11k pounds). Ultimately, it starts when I want it to, pulls what I ask it to, and hasn't let me down since the transmission failure, but it leaves a bit to be desired, so I am looking for some help. I have found myself living in a fifth wheel (approximately 13K all loaded up), and will eventually be hauling it to the Bellingham WA from Albuquerque NM, and hope to be able to travel regularly as well. Before I feel comfortable towing that sort of weight over the rockies, I want to get the following issues sorted out:

What I know about the current tune:
I have come to the conclusion that the pump has been turned up, but I haven't got a clue how much. The pre-boost fuel screw has been played with; there was no break off screw when I got to it. I don't know if the AFC has been played with, nor do I know about the star wheel. The break off screw is still present on the AFC housing, but it has a few knicks that are indicative of someone at least attempting to get inside. It seems to run out of steam around 2200, so I don't believe it has a GSK. The truck makes considerably higher boost than a stock truck will (35-40psi), and when towing up a grade, even with all that air, EGTs can get to 1300*, and it is only limited there by me backing off the throttle. The turbo appears stock (assembly 3533320; wh1c).

The Miss:
Having done a fuel filter (missing from lack of fuel), and experienced missing when the engine isn't fully warm, this appears to be something different. When accelerating lightly the engine sounds like it is loping, and in time with the lope is a vibration which seems like the engine is making considerably less power from one cylinder. Its rhythm is such that I think it is the same cylinder which is having the problem (not random at all in nature, very regular). The problem doesn't seem to be present at idle or high load, which is making troubleshooting tougher.

I can't recall if this was an issue before the transmission went out, or if it arrived with the new transmission, but because it is most prevalent from 1500-1900 rpm, and the frequency seems to stay the same relative to engine speed (as opposed to truck speed), I suspect it is in the engine or the input portion of the the transmission, with my money on the engine. The problem becomes more obvious when the truck is fully warmed up.

Has someone experienced this before?
-I have ruled out lift pump and fuel leaks because they would create a random problem not a regular one.
-I just re-set the valves, and none were far off, worst was .002 tight on the exhaust.
-I don't believe it to be ring seal because the truck doesn't blow much blue smoke and it doesn't seem to be a dead cylinder, just a weak one.I could be wrong here; I do end up with larger drip spots below the truck than most others I know from the vent tube.

My remaining theories are in the fueling system, but despite the writeups, I still don't have a really clear understanding of the fueling system once it gets to the injection pump.

-Does this seem like an IP, delivery valve, injector or nozzle problem?

If not, what does it sound like?

What would your next steps be?

Thanks in advance!
 

·
Premium Member
Joined
·
16,224 Posts
My next step would be to have the injectors tested or just replace them.
Wouldn't hurt to have the timing checked too.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #4
Does it do it in a free rev state, truck in neutral or park while accelerating ?
Hard to tell. If it does do it, it is far less pronounced than it is under load.


My next step would be to have the injectors tested or just replace them.
Wouldn't hurt to have the timing checked too.
This is the direction I was leaning. Do you, or anyone else, have info on identifying the injectors that are in the truck? I've come accustomed to the power it has. I don't know if they are stockers, or larger than stock. If larger, I'd like to get some of the same general capacity.
 

·
Registered
Joined
·
906 Posts
timing
injectors
injector lines
pump pressure tested for output pressure (last resort)

hope you like bellingham its wet as the dickens here, not at all like NM. which is where i wish i could be
 

·
Registered
Joined
·
11 Posts
Discussion Starter #6
timing
injectors
injector lines
pump pressure tested for output pressure (last resort)

hope you like bellingham its wet as the dickens here, not at all like NM. which is where i wish i could be
Are you thinking an injector line could be cracked? Or obstructed? I'd notice a leak, and I'd think an obstruction would have grenaded the pump prior to making it to the lines. Am I missing something?

I am not sure how I will feel about Bellingham. We're headed out there for grad school for the wife. I was stationed in Norfolk VA for a while, and I figure it was about half as wet as Bellingham. I could deal with that. We'll see.
 

·
Registered
Joined
·
549 Posts
The injector bodies will be the same if its stock or not because they reuse the bodies in most cases.

Your best bet is to get them tested, and see if they can be rebuilt if you want to keep them, but there are good deals on over sized injectors, just have to know where to look.
 
1 - 7 of 7 Posts
Top