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C2500 HD TD 'Burb dies, fires back up.

P

proth1975

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New (to me 'Burb) has some "issues".

OK... I'm driving along, 40 or so miles later, my 6.5TD dies. I pull over, it fires right back up. I go a couple blocks up the road, same thing. It does it once more. I get back on the freeway, and I'm good all 40 miles back.

The PO gave me a BOX of PMDs from eBay. He'd relocated the PMD to the bumper with some electrical tape.

So... this is a) my first diesel, and b) kinda freaking unnerving.

Any thoughts?

-P

'94 C2500 HD TD 'Burb
 
yes the fuel pump relay supplies the fuel pump electricity during cranking but after that the OPS takes over. there's a really good thread in the stickies
 
One thing at a time, fellas... proth, can you post a picture of what your PMD looks like? Does it have a heat sink?
 
Whelp... no pics, but the PMD was just electrical taped to the bumper. Just taped.

I built a Heath knockoff of my own, for about $12 in materials.

-P
 
It needs to be attached to the heatsink with a thermal heat transfer pad or some artic silver (thermal heat compound)...Most use the artic silver, put a nice even coat between the PMD and the heatsink and then weather proof it with a bead of RTV silicone around the edge and a dab on each of the 4 screws, to keep the water/moisture out.

After that you should be good to go.....Someone else will chime in, with better instructions, but those are the basics.
 
PMD's are not the only reason for stalling.... could be ignition switch, fuel supply problems, etc etc etc. The PO may have given you those PMD's because that was the only thing he could think the problem may have been. Unless he was purchasing a bunch of used ones that were already kaput.
 
PMDs aren't the only cause of stalling, but if you take a brand-new functioning pmd and tape it to the bumper like that, after 10 minutes there's an awfully high probability that's it.

That needs to be fixed, regardless of the root cause of your stalling, proth. Use thermal heat-sink compound as Louis indicates, and make sure your wiring harness is solidly connected and insulated.
 
I think, with reasonable certainty, that the lack of heat dissipation was what killed that PMD. After I had assembled my Heath knockoff, I fired it up and let it idle for a few minutes. After those 5 minutes, I could feel the heat on the bottom of the heatsync. So, it just being taped there previously did jack squat to keep it cool. I'm going to do a few other things that people have mentioned here, such as putting a relay on the OPS and taking a look at the lock cylinder, just to be sure.

Here's my new heatsync:




I used 5/16ths plate aluminum, sanded to allow the heat paste to get better contact. I used heat paste spread thinly and evenly, then twisted into place. A couple of allen-headed screws anchor it to the plate with threadlocker on the threads. I then ran a bead around the base with some copper sensor-safe RTV. All nicely bolted to the under-bumper location.

Not a bad job for less than an hours worth of work. I've got another piece of plate (1/4), that I'm going to fab up for a replacement (or just grins).

-P
 
Nice work! That looks like your problem-solver - but it's nice to have another one in case you need it!
 
Awww crap. Whelp.... code 36. (also 29, 46,49,71,76 but I had the cluster off for a few minutes). I just got done decrapifying the 'Burb by pulling the remote start. Had to splice a few wires back together (marine grade butt splices). I took her for literal "spin around the block", and she died on me. 4 times. Seriously?

So I'm assuming the "box-o-PMD's" I have is a crap shoot... I pulled a loser out of it. My makeshift Heath kit didn't help (yet). How do I test a PMD without hopping on the damn road? I have 10 more in there... but it could be all duds, and I don't want to really pay $300 for a new one.

I feel like I'm losing my freaking mind with this.

-P
 
Your best bet is going to be buying a brand new PMD because, as you say, that box of 'em is a crap shoot, and just because one of those used ones works now is no guarantee it's not about to fail a month from now. And. $300 is high for a PMD, unless you're getting it with the heatsink and wiring harness. IIRC, mine cost me $285 with a heavy heatsink, resistor pack and wiring harness extender.
 
Well, once you have a BBQ'ed PMD, it's reliability falls right off. Just because it's being cooled now, doesn't really mean that it will be okay later. There are a few that have attempted to retorque the transistor nuts. (Very very carefully that is) and had some degree of success.

Not knowing the history on the "box-o-PMD's" it is really a box of variables... or a box of good ones. Chances are if they were on EBay... they are just a box of chances. Not to mention, if the PO just electric taped them to the bumper... well, you may have a better chance of getting struck by lightning twice than having a dependable PMD in the box-o-chances. (That's a remote control guess, not a diagnosis :) )

I the stalling has gotten that repeatative, you could exchange PMD's and see if it does it as often or not. Switch back and see if it comes back. Diagnosis of a failed PMD can be caught with a scanner only.

A code 36 means long pulse... which may be an internal pump problem... fuel solenoid may be dragging. This may be electrical or need to add some lubricity to the fuel.
 
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