Question about 1998 Dodge Ram 2500 2WD

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Cummins verry rough idle no throttle response

Hello. ..98.5 cummins stock i have a verry rough idle and no throttle response, setting off codes po251, p1688, po253. Ihave installed a CKP sensor and no difference. would appreciate any feedback ,thanks marshallm.

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  • Steve Hart
    Steve Hart Jul 13, 2010

    How many miles on this? any other work done on the engine? has this ben slowly coming on ,, or did it just start doing this?

  • marlin_m Jul 13, 2010

    Hello moparhart,thers been nothing done to the truck its been trouble free,Theres 250 K so I guess its timefor some problems. I notices aprox 6 months pryor when hyway speed the motor would suddenly develop a weird vibration and sound but would clear as fast as it came, that happened a handful of times. This last time it happened it was completly different, it started sputtering and quit,woulnt start for about 15 min. when did start no foot feed and verry rough idle, just like it was badly out of time. It limped home. It will start but winds more before it fires,it seems when it does fire its when you let off the key. I have cracked the injector lines right at the head and there seems to be good pressure, the lift pump is original as is the V.P. Thanks for any help. MarshallM

  • marlin_m Jul 13, 2010

    moparhart i have tried this already it made no difference

  • marlin_m Jul 13, 2010

    I appreciate the code breakdown, what do you think the problem is the vp.



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Thanks for the info!
Lets start from scratch and see if we have a mechanical or electrical problom Disconect the batterys both positve and negitve
let it sit for a 1/2 hour. Then hook the batterys up try and start it.
lets see if you get a check engine light or if wee need to go intothe mechanical end, Ill be here on and off most of the day

Posted on Jul 13, 2010

Testimonial: "Thankyou for the imput.. MarshallM"

  • 1 more comment 
  • Steve Hart
    Steve Hart Jul 13, 2010

    ok Give me a bit here ill post the next step on this.. my computer is slow today ,

  • Steve Hart
    Steve Hart Jul 13, 2010

    OK sorry for the delay.
    Here is on the codes that you still have,
    P0251 - CP3 Pump Regulator Control; Injector Pump Fuel Valve Feedback: The ECM detects a discrepancy between PWM supplied to FCA and PWM returned from FCA.

    Possible causes:
    - Intermittent condition
    - Fuel Control Actuator
    - Return wire open from FCA to ECM
    - Supply wire open from FCA to ECM
    - Supply circuit shorted to voltage
    - ECM

    P1688 is Internal Fuel Injection Pump Controller Failure
    this can be seals or brass end sleve

    P0253 Fuel Injection Pump Fuel Valve Open Circuit.

    Problem sensed with fuel circuit internal to fuel injection

    Here is a link for the injector pump I thaught this is waht was going on i just wanted to dbl check by disconecting the battery
    Let me know if i can help more!

  • Steve Hart
    Steve Hart Jul 13, 2010

    Hi Yes i feel the pump will need to be replaced



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