Scary surging on 6.5..Acts like it's possessed..Need an exorcist or something??

[Daffy427]

The truck will drive along just fine and for no apparent reason feels like it's going to wide open throttle, like someone is stabbing the gas pedal..This thing is scary to drive..Anyone seen this before??? 1994 6.5 turbo,runs fine most of the time Thanks for any advice on this>>

[bow61509]

im not an expert but i would guess pmd or injector pump

[Avec]

I had the exact problem. I replaced the PMD and problem solved.

[gr8twhite]

Pump driver gone south.

There was a batch of flight systems pmd's that, when failing, went to a high side runaway.

[Daffy427]

Where is this PMD located??

[stockchev]

its located close to the motor, i suggest a pmd relocation while you are at it, thye over heat causing this problem

[Avec]

The PMD is mounted to the injector pump in the valley of the engine underneath the intake manifold. The easiest thing to do is to simply disconnect the wiring and plug it into the new, remotely mounted one. Just leave the old one where it is.

[Daffy427]

It appears that some one has replaced and relocated this unit to a heat sink plate on the top of the manifold.The PMD appears to be new. This truck came to us wrecked in front and I'm starting to think this situation could have easily caused the accident. The unit that's on it is called an FSD cooler,does anyone have any experience with these things??

[Avec]

Mounting the cooler to the intake manifold is the standard relocation, although not ideal, it is better than no heat sink and in the valley. Because you already have the relocation kit, just take the heat sink and PMD off the manifold and move it as far out front as you can. In front of the driver's side battery is very easy. I actually think my heat sink is an FSD.

In the past, PMD failures would be ever worsening stalling and not restarting. The newer batch of PMDs seem to be failing in the manner you describe. I have read about a number of recent failures that resulted in engine run-away. Stalling was much better, and less scary. My recent failure started with quick hits while at a stop light. Just a pop of extra fuel. Not a big deal with my foot on the brake. This worsened over time, then it became a situation where I would be driving at highway speed and it would go WOT. At first it would be for a second or so, but it quickly got to be much more than that and extremely dangerous. If the driver was in a bad spot, such as pulling into a parking spot and it went WOT, bad things would happen before the brake could be applied.

[Daffy427]

Thanks for the info and you were correct,the problem is gone. We installed a 6 foot extension and moved the thing out of the heat but I notice the PMD unit itself seems to operate at about 200 degrees,is this normal??? You don't want to touch it.thats for sure...

[Koots]

Glad to hear everything is working out for you! :cheer:

As for the operation temperatures, i believe it does run hot, which is why it's not good to have right in the intake valley.