Pulsating engine

[Halldoor]

I have a 1997, 2500 6.5L Diesel Suburban with an intermittent fuel
problem. The vehicle will start pulsating as if it is losing power then surging
back, the amount of drop off and surging is proportional to the speed you are
going at. While idling it hardly shows on the tack, but at 65-70 it will be
500-600rpm. It will also jack rabbit from a stop when you give the least amount of pedal.

I have replaced the pressure pump, fuel filter, fuel cap, and
accelerator pedal. My mechanic and I were told to check for air in the fuel line and didn't see any,

did a visual inspection of the fuel line and didn't see anything. My mechanic and I

are at our wits end does anyone have an idea of what it could be. In the mean

time I'm driving it till it dies then I might be able to find the problem.

[gmtech4]

TCC

 

(torque converter clutch )

 

get a different tech

[Halldoor]

I don't think it would have anything to do with the transmission being that also pulsates when were sitting in park. Mechanic said they found oil in the electrical connection to the fuel pump yesterday, but were not certain if it is actually the fuel pump that needs to be replaced it has less than 40,000 on this pump from GM. The engine surges forward like when your cruise control comes back on.

[scooby5121]

I have replaced 3 fuel pumps in my 6.5 diesel

and 4 fuel pumps in my 6.2 diesel...... from all the times at 1700.00 bucks a pop , I have only noticed lack of power pulling, head wind power loss, and top speeds of 60 kilometers/ 40 miles an hour while driving both of these trucks.

 

 

Serging, and intermintant rough idlie, etc what you describe would put me in a diesel shop. A real diesel shop........

and What Govtech 4 said too !!!!!!!!!!!!!!

Scooby

Edited October 2, 2013 by scooby5121

[scooby5121]

The monies you save on fuel , you put to replacing the injection Fuel Pump. Running additives would be your #1 choice after you get a new fuel pump, because the lubricating properties in the diesel has been reduced so you will be replacing fuel pumps frequently.. The newer diesels have a tank specially added to put in the additives because the sulphur ( lubricating qualities,etc) has been so reduced for clean air.

 

IMO, scooby

Edited October 3, 2013 by scooby5121

[gmtech4]

ok,fair enough ,what about the PMD on the side of the injection pump,?

 

clarify "fuel pump"

 

"lift pump" lives on the frame,,pumps fuel

 

"injection pump" does the work,lives between the heads under intake manifold ,,,

 

loose the engine cover if not already ,,,

 

relocate PMD in the bumper holes to cool it better or anywhere where air is moving ,,,

 

did anyone scan this truck in the last 15 yrs ?

[Halldoor]

The lift pump has been replaced, my fears been that was injector pump it's going bad. We have just over 40,000 miles on this injector pump as it is I was hoping it would last longer than that. We had pulled the cover yesterday to physically inspect all the wiring harness going across the top just to see if there's a physical damage to it. I had wanted to check to see if this Marvin because I'm parking problem or something electrically shorting that was causing the substation from vibration. When mechanic told me they found oil in the actual electrical connector To the injector pump I knew them it was probably the culprit.

[gmtech4]

how does oil get to a connector of the injection pump,???? it cant !!!

 

the problem is that the injection pumps can fail with different symtoms (trust me )

 

i went thru a few on my old 6.2,,,,,1 pump lost power over time on a drive across canada ,finally dies 5 KM from my destination lol

 

that new one did the same driving across a small town ,,,,so same lose of power but different duration,

 

take it to a diesel shop and at least road test it WITH a tech ,,,no use guessing here