pmd failure or resistor failure?

[rank]

Truck is a '95 Suburban 1500 and the fish bites recently turned into shark bites, then whale bites and runaway scenarios accompanied by massive black smoke.

Took it to GM dealer and they read code 35 which tech said is PMD failure. When I describe the runaway scenario the tech said it was the IP for sure and proceeded to write me up an estimate for $3500 installed.

Spoke to diesel service guy I bought my new PMD from 16 months ago.. He said could be PMD or IP.

Spoke to former GM mechanic from the 6.2 and 6.5 era. He said IP.

Spoke to another GM mechanic from that era. He said PMD.

Spoke to another diesel service guy, he said "Code 35 could be anything from PMD, to IP to a failed resistor, but from the symptoms you describe, don't waste your money on the PMD. It is the IP for sure." Well he was wrong.

I located a running when wrecked 1999 Silverado and borrowed the remote PMD. Problem solved. So know that I know the PMD is the culprit, I am wondering if it may be as simple as a resistor inside the PMD. Has anyone actually tested and repaired a PMD?

$400 every 16 months for a PMD is kind of silly. I have a feeling these diesel shops swap in a $2 resistor and charge me $400 for the one I traded in 16 months prior.

[jerrey]

Older versions of the PMD made by Stanadyne usually fail and leave you stranded with a none running truck. There are more recent PMDs made by an aftermarket manufacturer called Flight Systems that occasionally go into a runaway condition when they fail sounds like that is what you experianced. To my knowledge no one has ever had any luck with repairing a PMD. Do a search for PMDcable on Ebay he sells the newest Stanadyne PMD for $210 with a two year warranty. If you do have a good remote mount setup with a new PMD outside the engine bay you will likely never need to exercise his warranty.

[57diesel]

My local shop says he has had very little trouble with the grey Stanadyne ones. That is what I was thinking of getting for a spare.

[racer55]

The last report I read from PMD Cable said that to date they have only had 1 warranty claim on the grey stanadyne-that was a couple of months ago now but might well be still valid.
So until the old stock flight systems PMD's are all gone and the new version proves itself,I would go with the grey stanadyne,actually I did-have one on the shelf waiting until needed.

[JMJNet]

If you search this forum, there is no way to repair PMD.
There was a few people that promises the circuit diagram and those people are never found again in the forum. Not sure why.

The test is just put the PMD in the truck and see if it runs.

The bench tester is not working because even if it passes bench tester, it can still not running or starting a truck.

[FloridaHorseman]

Originally Posted by rank

... I have a feeling these diesel shops swap in a $2 resistor and charge me $400 for the one I traded in 16 months prior.

PMD resistors are about $20 and the PMD will work without one. It's just a "fine tune" device to make up for differences in manufacturing tolerances.

If you're gonna be a 6.5 jockey, get the remote PMD mounting kit and move it out of the engine bay. Also carry a spare known-to-be-working PMD. Sooner or later you'll need it. It's the Achilles Heel of the post-'93 6.5 ~FH

[PrivatePilot]

Your symptoms are stereotypical PMD failure. All the varying answers and BS you got from the mechanics etc etc are not surprising since even most mechanics are often clueless about the 6.5 - they immediately finger the IP (often because they just don't know any better, and the IP has a bad rap on the 6.5) and then they sit back waiting for their $$$ profit to roll in from people who take their word for it.

The resistor will not cause your symptons...whatsoever.

Remote mount the PMD outside of the engine compartment on a good cooler and you'll probably never have to worry about it ever again. I'm running a $35 eBay PMD for 2 years and counting now, mounted behind the grille.

[rank]

Ok thanks for the replies. I did a search before posting and did find a good thread about resistors. There was some difference of opinion however and I thought I'd post this Q up so see if there was any new info.

All the PMD sellers around here want the old cores. I figured there must be a rebuild trick.

This is the 2nd 6.5 I've had a relationship with. Used to carry a jug of water to pour on the IP in the old 1999 Silverado. Then we moved to a black Stanedyne mounted on a pretty trick looking black heat sink with "FSD Cooler" written on it in neon green letters.

16 months ago when I replaced the original PMD in my --ahh, I mean the wife's--- "new" `95 Sub, the fella I bought the PMD from mounted a steel bracket on the intake manifold, then mounted the PMD to that bracket. I promptly went to a computer store and bought a heat sink with a DC fan mounted to it and mounted that to the PMD. It looked kinda racey.

I guess it's PMD cable for the grey one this time.

[racer55]

Best to get the PMD/heatsink/resistor combo out from under the hood.
A 6' extension harness is the way to go so you can mount it behind the gril or under/behind the frt bumper.

When it comes to resistors there is a very slight gain in fuel quantity if you go with a #9,anything from a #5,7 or 9 is fine.

Also if the PMD is currently mounted under the hood and the harness ground id fastened to the heatsink-get it back in the stock location on top of the IP under an OS screw.

[JMJNet]

Originally Posted by rank

All the PMD sellers around here want the old cores. I figured there must be a rebuild trick.

They sell it again??? as USED TESTED. They don't say it as GOOD.