2500 Ram Diesel Throttle Problem

I have a 2002 Dodge Ram 2500 pickup with the Cummins diesel and automatic transmission. Several weeks ago I started intermittently loosing throttle control in the middle range of the gas peddle.

I would smoothly depress the peddle bringing on more power and get to a dead zone where more peddle movement did not increase power. I could pump the peddle through this dead zone and get no throttle response. If I floored it, it would downshift and I would get power. Yesterday I pulled out onto the road and only got 10% power with no throttle response moving the peddle through 90% of it's range. I moved the peddle from no throttle to flooring it. It would go to idle but rise no higher than about 10% power. This lasted for about one minute then "poof" it works fine and I have full throttle control again. The problem is totally intermittent. I have not noticed any difference with outside weather (humidity, temperature) or if the engine is hot or cold. The problem occurs when the truck is empty and when pulling a load. No idiot lights are illuminating and no code has been set in the computer.

When it's working I have good controllable throttle and power so I do not suspect a fuel filter. Also, the fuel filter was changed just 200 miles before the problem started.

I suspect the throttle position sensor but it's not a cheap part so I hate to replace it with nothing by my guessing.

Anyone know what might be wrong?

 

These things are weird. Everyone thinks of a diesel like in a road grader. Not so with the Cummins. There is very little mechanical being done under the hood. It is mostly done by computer. Like you said, the TPS would be my first suspicion (as it is a classic symptom), and it ain't cheap. When you put your filter cap back on, you didn't cross thread it, did you? It is so easy to do with that plastic against cast situation. If you are sucking air at any point it will act wiry, like that. Have you released your water-in-fuel valve to purge it? I know your dash isn't indicating it, but you could have trash, and not actually water there causing a problem. Collect it and see what it looks like.
How many miles on the engine? Do you have a service manual on it? PM me with that info.

 

Thanks for the tips but it acted up again today and set a code. It's the injector pump. Now I can only dream that it was a $600 TPS assembly. Related to the injector pump there is also a bulletin to bypass/remove the transfer pump up at the engine and install a pump in the fuel tank. It's possible that the failure or under performance of this pump may be the cause of the injector pump going. All totaled I think it's going to be about $4'000.

 

OK, at least you won't be spending money on parts you don't need. You can get a remanufactured pump (face it, there aren't any new ones) for $750-900. My guy did a R&R for $350 I believe. If you are still running the stock lift pump, you are gonna have to change it anyway, BUT don't do an in-tank pump. That's Dodge's answer. I'm running an aeromotove frame mount, but your better pumps are going to cost you $500+(Fass). Next, do you have a fuel pressure gauge. Next on your list. If you catch it in time and put a good lift pump, mounted right under you on the frame, you will be better off and may forestall the injector pump inevitability. You don't want to be running less than 15psi at idle and 10 psi wao. Your stock pump will be lucky to put out 5, so there is where it started. Fix that and you may get a new lease on life. Did it pull P0318 code?

 

Sorry, I washed my hands/notepad so I lost the code I'd written down. It sounds like you're familiar with the problem. It was probably made worse because for 5 or 6 years I had a Power Puck plugged into the pump which I'm sure did not help the fuel pressure problem. My mechanic is ex Dodge so is going by there book with a new pump ($2'100+) and the kit to re-locate the fuel pump to the tank ($860). Add in sales tax and labor and doing it the Dodge way gets to $4k in a hurry.

Thanks for the advice. Needless to say, tonight I'll be searching for a remanufactured injector pump and checking out other pump options. Long ago I installed a EGT gauge ahead of the turbo and I've always wanted a transmission temp gauge. It sounds like a good time to put in a three stack on the A pillar and include fuel pressure.

 

I'd say Larry is the man on these issues...

Though why 2 people I really respect would drive Dodges is beyond me....lol.

Wasn't a diesel and it was prob more the dealer...but never again.

 

I have a remanufactured injector pump on the way and an Air Boss fuel pump kit for $1'360. Much better than the $3'000 price quoted by my local NAPA store.

My mechanic friend called a buddy of his who is a retired engineer from Cummins. He thought Dodge screwed-up with their fuel pump and Bosch had problems with the VP44 injection pumps. The Dodge pump was marginal to begin with and only got worse with time. And, apparently there is a solenoid inside the Bosch injection pump that likes to fail. This solenoid 98-01 had a steel sleeve which if there was water in the fuel and the truck sat for a while would cause the sleeve to rust and the solenoid would stick and fail. For 2002 they changed to a brass sleeve to solve the rust problem but the brass was too soft and galled causing the solenoid to stick and fail. Overhauled/remanufactured ones now use a stainless steel sleeve.

Thank you Chandler. You saved me a ton of money and the advice to NOT do Dodge's in tank fuel pump seem to be spot on. The engineer specifically said do NOT do Dodge's fix of putting the fuel pump in the tank. He thought it was not much better than the orifinal one and it was an expensive fix. He thought it better and cheaper to go with an aftermarket pump.

 

Way to go!!! You won't be sorry for getting the Air Boss/Reman Pump combination, and what a good price, too! Good information from your engineer buddy, too. I knew the problem wasn't "mechanical", but had to do with the electronics of the VP44. This is good information. I think the SS sleeve would have made sense in 1998, doh!
Yes, the in tank is better than the old lift pump, but you lose accessibility, and the frame mounted ones work so much better, at better pressures......speaking of which.....do it. Triple pillar mount. I only have fuel pressure, now, but I scan it as often as I do any of the gauges, it's that important.
Man, you got me worried. Mine hasn't been driven since surgery over a week ago, and I am sure it is lonely. Mustered enough leg pressure to push the clutch to start it (gosh I love that rattle!). My guys won't drive it......"I ain't gonna drive no stinkin' straight stick!" Sissies.

 

Vic, in reality you could take my drive train and put it in a Toyota and I'd be happy. It ain't the "Dodge", but the "Cummins".
Dodge makes it......Cummins shakes it.

 

I also have a '03 Dodge and it's just not the same. Dodge made it too quiet and they shrunk the turbo. Sure, it accelerates more like a car but it does not have the lungs for pulling like the '02. The '02 takes a while to get going but once the turbo is whining it keeps pulling. Of course I have to turn the engine off at drive-up windows so they can hear my order.

 

Yeah!! I know..........."you want ??" I just get in the habit for fear of their messing it up royally!! Plus being a 3500 dually it sits so far off the ground you have to reach so far down! And bank ATM's forget it, you have to get out anyway.
Pulling our mountains I find once the turbo gets wound up 4th gear is a super puller. Now from a standstill at the redlight at the bottom 1-2-3-4 inhale, takes a little doing. I do like the 1400 RPM 60 MPH, however in 5th.