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PMD ?

ak diesel driver

ak diesel driver

6.5 driver
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So I have a ? about max fuel ouput via PMD. The couple of times I've been in a truck that had a PMD fail wide open it seemed to be putting out more fuel than normal wide open throttle. Also others accounts I have read seem to agree with this from the standpoint of billowing black smoke etc. So is it possible that it's actually putting out more fuel and the next ? is it possible to simulate a PMD WOT failure? Would be interesting to test it out if a guy could simulate a failure.
 
100% agree the failures I experienced were the same- more power than just going full throttle. First time I experienced it, I thought it was an oil suckin runaway.

Second time I say it, I had the GM engineer for the cooling system problems in the truck with me. We had previously spoken about pmd run away and he dismissed it. When it happened with him there- I stopped the truck and slammed it in park. I stopped him from turning off the key and showed him the pedal was up. The truck SCREAMED at 4,600 rpm. I let it run like that 5-6 minutes. He was yelling saying "look at all the smoke, it's an oil run away."

It was not as much smoke as a real run away- more like heavy acceleration with no boost.

When I finally shut it down there was no oil used up. I swapped pmd on roadside& drive the truck back to the shop. We installed pmd on another truck- instant run away, shut down and the engineer took it with him for testing. Never heard anything back- they said tests found nothing.

Long winded point (as usual) being its all fuel, not oil doing it. And having used propane before on a different truck- it felt like that- full throttle plus propane.
 
NVW said:
Smoke could be the ecm cutting boost but max fuel is delivered.
Click to expand...

^X-2. Am leaning toward this as well.


Am thinking that the easiest way we can really isolate whether it is black smoke from lack of oxygen or more fuel than commanded is to put a known bad PMD on either a turbo with no wastegate or one with a turbo-master; this way there is no ECM to limit the boost.

Another possibility is to put on a scanner which can read the fuel flow. Naturally this presumes the scanner can see the fuel flow per sensor and is not seeing what the ECM is commanding.
 
JayTheCPA said:
^X-2. Am leaning toward this as well.


Am thinking that the easiest way we can really isolate whether it is black smoke from lack of oxygen or more fuel than commanded is to put a known bad PMD on either a turbo with no wastegate or one with a turbo-master; this way there is no ECM to limit the boost.

Another possibility is to put on a scanner which can read the fuel flow. Naturally this presumes the scanner can see the fuel flow per sensor and is not seeing what the ECM is commanding.
Click to expand...
To the best of my knowledge GMTDScantech can read commanded and delivered fuel rates. Not sure if it is from the OS or what the ecm commands.

I wouldn't want to be the guinea pig in this test.:D
 
I'll Guinea pig, I just need to borrow somebody's truck to...uh... Help a friend move....yeah that's it -help someone move. (Yes, I'm funny on my home planet)

No on cutting boost, we had a gauge on the one I tried to let blow up. I THINK it was 5ish psi, but can't remember. I've slept too many times since then. The truck was sitting still mind you. I can't remember what the boost was while we were under load.

We wanted to know what happened so we could flip a switch to go mode as well. I think if GM could have figured it out then, no one would be experiencing it now. Iirc this all happened in 1999-2000. I know it was before 9-11.
 
In theory I have to say yes because of how that happened. But according to a few of the programmers out there, they can set it to call for more but it doesn't deliver. Maybe it's maxing out the fuel while doing something stupid with timing that they would never put in their on purpose.
 
Have the same thought about whether the electronics can deliver more fuel. Especially where I am seeing commentary that the ECM has hard coding to only command up to something like 95 mm^3 of fuel (or possibly a bit higher / lower) at WOT where the DS4 is capable of 120. Have also seen commentary that fuel flow at WOT is an issue where even with the common lift pumps, the IP cannot ingest its full potential at WOT due to merely not enough fuel. So, getting more fuel is probably going to need multiple part modifications and not just the PMD.

One thing that I remain curious about is whether it is possible to modify the PMD's output voltage to get stronger plunger motion. Reason for the thought is that I know in the 7.3 DI community, they modify their equivalent of our PMD to deliver more voltage to the injector which forces it to open quicker and effectively deliver more fuel. Ok, sure, the DS4 does the job of triggering the injector for the 6.5 IDI where in the 7.3 DI the injector does it, but it still has me wondering about whether a modification to the PMD's trigger voltage will have any effect.
 
Going off memory that I've tried to forget, but the 7.3 di engine: they would bump the voltage (high voltage) to the injectors only after bumping the second high pressure oil pump that is the force multiplier of the 2 stage injectors. The added oil pressure had to be overcome. The huei(?) set up.

The idi 7.3 used the regular pop it style injectors similar to ours that used the regular injector pumps.(db2)

Tired this am, might not be thinking right:inpain:
 
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Reading other posts and couldn't get this out of my head. I don't recall ford ever using any ds4- they only had db2, then the power stroke.
 
Yes, from what I recall, the 7.3 IDI used the DB2. Do not recall what the 7.3 DI used for its IP, and am confident it was not a DS.

About the 7.3 DI's voltage mod (IIRC, IDM mod), correct the voltage to the injectors was increased (IIRC OE was 120 and the mod was 140), but do not recall that other changes were absolutely necessary (or more specifically, the voltage mod still helped even with OE level parts).


Back to the thought though, will a voltage increase from the PMD to the DS4 make a difference . . .?
 
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