I bought my first cummins last spring, it has been great. I've put 20,000mi on it. I drive it to work and back and also am self employeed: I have a skidloader(8,000lbs plus 26ft trailer in tow) that I do custom work with, I also haul horses(24ft by 7ft livestock trailer). It now has 184,000 miles and I am having my first engine problem. When I take off and take the RPMs up to 2500 or more, the engine cuts out/sputters/feels like running out of fuel. Also, while sputtering it blow blue smoke. Then if i shift into 2nd gear it goes away until i get up to 2500+ RPMs then it does it again. It will happen usually only in 1,2,3rd gear and usually only when the engine is cool or cold. I also think the MPG has dropped off. I have run several tanks of fuel thru it: with and with out additive. Also changed filter twice withing 5000 miles. The air temp doesn't seem to matter, it happens whenever. It uses little to no oil. So, my theory is one or more of the following: valves need adjustment(last time unknown), bad strainer in the preheater, failing lift pump. Please advise.

I am going to change the strainer and lift pump at same time, as well as have the valves adjusted. Please let me know if I am doing anything unnecessary.
Thank you for any help. I am a new member and this is my first posting.

 

Sounds like you need to get the timing checked, injector pump timing that is.

 

If its doing it only when its cool or cold I would write it off as normal. I have 16° of timing and it still does it. Cylinder temps arent up high enough to completely burn all the fuel entering, so it breaks up and stumbles. If it did it alll the time Id say yes to timing, or to air entering the fuel system.

 

I second the injection pump timing. Over time it will slip down and cause the truck to not run good on the top end. Also Welcome aboard.

 

check your overflow valve I had one do the same thing and that is what it took to cure it.

 

My bet is it's low fuel pressure due to a bad overflow valve. I wouldn't replace the lift pump just yet, it's likely fine.

Replacing the OF valve is a five minute one wrench job if you don't drop the sealing washers, stuff a rag under the valve to catch a falling washer. Remove the old valve and put new one in it's place. Occasionally the notch in the manifold you see to the left of the OF valve in the picture needs to be filed or ground a little to allow the old valve to be removed. Don't bend the line to remove the valve, it will make it very difficult to line up again. New style OF valves don't always have the retainer on top that says not to remove, don't worry it's just a design change.

The object in the lower left corner is the oil fill cap.


You won't find a better price on an overflow valve than here

Precision Diesel Injection and Turbo Inc.
Marty Tompkins
888-734-7349
$35 + $7 shipping and handling.

 

I Third the overflow valve then if it still does it I would move to timing. Chances are your overflow is bad anyway and for the 35$ + 7$ shipping its cheap enough to figure out.

 

That

plus no GSK, and a stock plate will usually defuel hard at 2500 RPMS.... just another point to consider along with the overflow valve.....


Rick

 

Is you truck stock? If so 2500 rpm in 1st gear should be avoided anyway especially cold.

 

Don't want to hijack his thread but I have a stock 98 thats doing almost the exact same thing, except at about 2200RPM and is a total dog in 5th gear. OF has been changed but I haven't put a gauge on it yet for FP.

 

Again if it is stock,

they are known to defuel at about 2200 RPMS, I would change out your fuel filter just to be safe, and then put in a Governers spring kit to solve the problem of defueling..

Rick

 

If it's a 94-95 spd defuel should occur at 2450, but if it's a 96-98 5spd defuel should hit about 2700 on a perfect running truck.

With that many miles I'd be checking: overflow valve, lift pump pressure, cracks in rubber fuel hoses, melted fuel heater wiring connector letting air in, and reset timing. The 96-98 5spd trucks are the worst for slipped timing.

 

Where is the fuel heater, and how do i check to see if I could be sucking air there? My truck still pops after timing, and an overflow valve... Im guessing now either a weak lift pump, or possibly sucking air as suggested. My truckl has done this ever since i have had it, and is worse when cold.

Eric

 

I use compressed air though the tank fill, no more than 10 psi, to find leaks.

 

dont worry about ur pump...its nearly bulletproof...3k gover springs and a timing advance and you'll think you have a new truck