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Daniel Jones
Daniel Jones,
Category: Chevy
Satisfied Customers: 504
Experience:  GM A Tech at Straub Buick GMC
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I have a 98 chevy with the 6.5 turbo diesel and it's running

Customer Question

Hi I have a 98 chevy with the 6.5 turbo diesel and it's running really bad at idle. How ever when you try to give it any throttle it floors itself or jumps all over. When you put it in gear at idle it will smooth out. I replaced the gas pedal already with no change.
Submitted: 1 year ago.
Category: Chevy
Expert:  Daniel Jones replied 1 year ago.

Hello. Welcome to the site. Thanks for coming. I'm ***** *****.
I'm here to provide as much information and insight as I can, to best answer your question.

Have you checked the system for any codes?

Thank you for posting your question.

Your business is very valuable to us.
Thank You
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Customer: replied 1 year ago.
I got a code p0251.
Expert:  Daniel Jones replied 1 year ago.

Here is a description of the code and how the system works. You probably have a pump going bad. I have also done a few of the Pump Mounted Driver(PMD's #1 in picture), which is mounted to the side of the pump. They have a relocation kit for them. You can mount it to the wheel well away from heat of the engine. You don't need to remove the old one from the pump, just unplug it.

DTC P0251 Injection Pump Cam Sensor Circuit

Circuit Description

The optical sensor provides a pump cam signal to the PCM by counting pulses on the sensor disk located in the injection pump. The pump cam is one of the most important inputs by the PCM for fuel control and timing. This test monitors the number of crankshaft position pulses that have occurred since the last cam pulse. The physical one to one correspondence between the pump cam and the crankshaft implies if more crank pulses are detected than cam pulses, cam pulses have been missed.

Conditions for Running the DTC

  • The PCM performs this DTC diagnostic continuously.
  • The engine is operating.

Conditions for Setting the DTC

  • The number of consecutive missing cam pulses is more than or equal to 8.
  • All diagnostic set conditions met for 2 seconds.

Diagnostic Aids

Intermittent DTCs (P0251, P0370 and P1216) may be caused by air entering the fuel system when fuel levels get below 1/8 of a tank while performing hard acceleration or turning maneuvers. It's also possible that a P0251, P0370 and P1216 will set the if vehicle has run out of fuel. Customer driving habits should be checked to determine if the vehicle has been performing in these manners. If the vehicle has been performing in these conditions, bleed the fuel system of all air and test drive the vehicle.

When the PCM is in backup fuel, fast idle and poor performance problems will exist.

An intermittent condition can be caused by the following:

  • Poor connections.
  • Rubbed through wire insulation.
  • Broken wire inside the insulation
Expert:  Daniel Jones replied 1 year ago.

Hi, Just wanted to get an update on how you made out with vehicle.

If you need more help, please use the "Reply" tab to continue our conversation - I'm happy to answer follow-up questions.

Please take the time to leave feedback and Rate my service for my response to your question.

Thank You for posting your question.

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