OT Diesel experts

[Brad Buchnan]

Elsewhere on this board I read about a leaking injector causing a runaway engine. I have a 6.5 GM diesel with this problem and am just about to change the injection pump to try and solve the problem.

Question: Could the injector be the problem and if so how would you test each one to find the culprit??

Thanks in advance,

Brad

 

[Brian Jasper co. Ia]

If you're having un controlled engine speed, injectors aren't your problem. That engine doesn't use common rail injection. The Duramax does. A stuck open injector on a Duramax will usually melt a piston. Engine speed is controlled by the injection pump on a 6.5. Exact method of control varies a bit with model year of production.

 

[Bob]

A little more info would be helpful.

Is it an early mech injection unit, or a later EFI system?

How did this come about.. was it running well, then just began to "run away" or was it sitting for a while, then acted up when put back into service?

Is it the turbocharged version, or naturally aspirated?

If turbocharged, the engine can overspeed if the turbo seal fails and it begins burning crankcase oil.

For that matter, an NA version can overspeed if oil comes through the crankcase ventilation system and enters the intake manifold.

 

[bison]

A runaway 6.5 is caused by 2 things.

1) a broken pump shaft(usually runs eratic,hard to control)
2)a faulty PMD (pump mounted driver) the black module the size of a deck of cards on the dr side of the injection pump.
The new "improved"style grey stanadine and the aftermarket D-tech PMD's both have displayed this run away symtom.

I vote you got a faulty PMD.

 

[bison]

Forgot to add,
the 92 and 93 model 6.5 have a mechanical pump.
94 and up are electronically controlled.
Drive by wire.

 

[Bob]

Broken pump SHAFT and still runs... please tell us more about that!

 

[Brad Buchnan]

Thanks for the feedback. This is a '95 turbo-diesel with low miles on a reman. block. The revving problem began as a run-up after starting and in the early stage would eventually correct itself.
Now the truck starts easily but idles at 2000rpm. also the throttle is like a light switch- either full throttle and black smoke or idle.

Brad

 

[Bob]

Do you have a "check throttle" light?

 

[Brad Buchnan]

No codes at all. Changed the 'fly by wire' throttle pedal. PMD has been changed recently. I plan on replacing and 'remoting' it also.

Brad

 

[Bob]

What PMD are you using... Stanadyne or Flight Systems?

Recently, a neighbor used a Stanadyne, it lasted only about a year and not many miles. About the same time I installed a Flight Systems unit which is working.

If you have access to a spare PMD you can plug it in without mounting it (to the pump or external heatsink) and start the engine just long enough to see if the problem goes away. If you have access to a proper scantool you can see if the 'puter is commanding the long injection duration or not. If the 'puter is NOT commanding it high fuel rate it's got to be a PMD problem, wiring problem, or the solenoid in the pumping head is stuck CLOSED.

I'd better get to the shop now, or NC Wayne will make me look bad!

 

[bison]

Most likely you got a Broken pump shaft,replace Injection Pump.
If you can't find a reasonable priced reman,
I got a few dealer take offs here(pump is good,PMD was fried)
Email me if interested

 

[Brad Buchnan]

Thanks to all for the replies!!

I think my path will be to buy a new PMD and aee it it solves the problem.

Probably not a bad thing to have a spare in any case.

Will update in a few days.

Brad

 

[bison]

The pumpshaft has a square only 1/8" long at the end where it engages the rotor,a little chip on a cornerbroke off throws the timing off as it can rattle back and forth, as does a shaft thats broke diagonal.

But that should've set a code,he says no code.
A faulty PMD seldom sets a code.
a number of he latest new flightsystem PMD have runaway problems.If he has one off those it may well be the problem,altough the faulty PMD's usually run the engine all the way in the redline.

www.TheTruckStop.com is an exellent source for info and repair dealing with the 6.2 and the 6.5

 

[guido]

Hello bob,
It does go wild for about 2 seconds, no governor controll,and then.....................silence.
Guido.

 

[Brian Jasper co. Ia]

It's not going to run with a broken pump shaft...