My 91 ram 250 recently developed a very rough idle that comes and goes. I replaced the fuel filter but still have the problem. It may be getting worse......todat the engine quit altogether. It runs fine at higher rpm, and starts easy. Engine has 140,000 miles and has had excellent maintainence. (former owner changed oil every 3,000 miles) There doesn't seem to be any smoke from exhaust during the rough idle, and engine has plenty of power. I also tried draining the fuel filter even though the "water in fuel " light wasn't on. Any ideas?

 

Ravenwood220;
If it were me I'd try running a fuel additive like powersevice (dirty injectors or bad tank of fuel ?)though it dump a pint in a tank full and run it through and see if that helps. If it dosen't I'd consider replacing the lift pump, "$70 through cummins" I don't know what your milleage is but my first pump was weak at 170k. The Bosch inj. pump is capable of pulling it's own fuel but if it's a little tired "high millage" then that my very well be what's going on.
ramguy

 

Ravenwood220, another simplething to check is the wire for the fuel shut-off. If the connector is loose or dirty, you might get an intermittent situation, especially at idle, where the engine doesn't have enough momentum to hide the symptoms.

Just a guess.

 

All good ideas above, but my truck did the same thing. Replaced the lift pump (191,000) and cured it for about 2 days. What the heck? Thought I got a bad pump so I replaced it again. Good for about 30 miles. Got scared and went home. Replaced all the fuel lines, took out the tank sender and was about to lose control until I remembered a post about taking out the fuel shut-off valve and checking for metal filings. Guess what- Injection pump time!! So, if all else fails, give it a shot. That was my first experience with trying to diagnose a bad injection pump, and it took me awhile. But, I learned a lot. Good luck and I hope it ISN'T your I-pump. Jim

 

Thanks for all the ideas..........I am starting to worry though. 2manydogs description fits my symptoms to a "t", and I also have too many dogs! My wife's latest addition, a white, small, yappy waste of space put us in that catagory! I remember when the injector pump went out on my John Deere tractor, it was quite expensive. (Especially when the first overhaul lasted 15 minutes before the shaft sheared off, and the rebuilder refused to accept any responcibility!) If it does turn out to be the injector pump, what is a ball park cost, and can anybody recommend who to go to? My truck has to be dependable...........I consistantly haul some rather expensive equipment from job to job, and breakdowns on the road need to be the least of my worries!

 

Also......I am rather new to Diesel engines in a pickup. Where is the fuel shut off valve 2manydogs was talking about? My truck is a 1991 Ram 250, 4Wheel Drive Automatic with 140K miles

 

Im not sure of the 1st gen but im sure 2nd gen 12 valve is same price and lift pump are a little more than $150 and the injection pump is around $2000 I thought.
more should chime in their 2 bucks worth of info though
good luck.

 

Our Cummins dealer in Reno seems a little high, the lift pump was around $70. The Injection pump was $900 through Diamond Diesel out of Sacramento. The fuel shut off is on the top rear of the pump with 2 wires going to the top of it. You have an auto, so I don't know if the bracketry? is in the way. Some one else might tell you about a piece you can cut off of it to get to it, I'm not familiar with it. Enjoy your new Micro-Mutt Jim

 

check piersdiesel.com for the injection pump. He had them on sale a while back.

 

I am not sure this applies as my truck is newer, but i had the same problem with the intermittant rough idle. The truck would miss so bad it would almost die when returning to idle. I pulled the filler hose loose with the truck parked at an nose high angle and proceeded to siphon every drop of fuel out i could get. Then replaced the fuel filter. went to a different filling station than i normally use and filled a 5 gallon can with what i hoped was good diesel. poured it in and primed the fuel filter and fired it up. No more intermittant rough idle. runs sweet. Hard to find good fuel here where i live

 

Take a look at the injection pump, and look for a small electrical pigtail that hooks to the ignition hot terminal. That is the fuel cutoff solenoid wire. It gets frayed right where the wire enters the housing, and can ground out and cause the pump to shut down.

However, from your description of the problem I suspect it is the lift pump. The VE pumps relied on a diaphram type lift pump (like gasoline engines used to use) and it gets tired at about the mileage you list. Cummins, Piers, or any number of places can get you the necessary replacement lift pump. There were rebuild kits available from Cummins for the huge sum of $20, but I do not know if they still have them or not. If they do not, and you are good at mechanics, a Case-IH tractor dealer will have them for the early 5.9's used by their tractors - same lift pump.

 

Hey guys!
Thanks for all the replies and suggestions. I started with the easiest and cheapest fix first. I added a fuel additive that claims to clean injectors (and also re-chrome the muffler bearings!) Drove about 300 miles with absolutely no problems! I also found a bad wire connection on the side of the injector pump. I don't know what it is, but I did fix it. I am reasonably sure it is not the fuel shut off.....I located the shut off valve at the back of the injector pump with 2 wires going to it. Those connections were good. The connection I am refering to looks like a small solenoid on the side of the injector pump with one wire going to it. When the engine was running, I could disconnect this wire with almost no effect. I say "almost" because there seemed to be a very slight hesitation or flutter in the idle when I disconnected or reconnected this wire. I also noticed a spark when I reconnected the wire, so there definetly was current there. Anyone know what this is?
I have a gut feeling that my problem is going to come back soon, and if it does I will replace or rebuild the lift pump. I will keep posting my progress just in case anyone else out there is having the same problem.

 

I would also check it over real good for air leaks in the fuel system. Mine is a later model but I have had some problems along this line caused by air allowed to enter and under low rpm caused some roughness.