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6.5 “pops” & blows black smoke intermittently

PMD Harness Black Ground wire attachment to IP Body just above the data plate next to the Optic Sensor. Same point should be used for the extended harnesses. Other's will have to explain why as my understanding stems from the '5 monkeys in a cage' scenario...that's the way its always been explained around the forums.
56176
 
there's nothing about the IP that constitutes a good ground. there's a gasket between the IP and the housing everything else would probably get a spark if you hit it with the positive wire from the battery but the PCM is pretty finicky about having a constant ground
 
Ray2377 said:
OK. The wiring harness from the pump has he pink wire broke at the connector, so it’s butt-spliced to the connector to the old pmd. The old pmd has no resistor and a small amount of corrosion on the connector terminals. I plugged the new one in and idle tested it. Both seemed to run the same while accelerating at idle.
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@Paveltolz is correct in "harness is suspect". Yes, ground it at the proper spot and don't add grounds. Added grounds become ground loops that can smoke wires when you hit the starter and have a bad ground on battery cable or two.

Did you wiggle the harness with the engine running to see if it acted up, stalls, or makes the pop noise. Do expect the noise so you don't jump so bad.

Corrosion may be deeper than the surface connection you see. The butt splice may be a green mess.

If it was mine and I wanted it to run I would replace that harness. Maybe fix it with a soldering iron. But the crimps at the wires may be corroded in the GM connector.

Can you post a pic of the butt splice? Not clear if it's the IP harness, PMD extension cable, or engine to IP connection.
 
Is there another connector end at the IP or does the harness end in a hard wired connection? I would like to just replace that harness so I can use the new lead with my new PMD.
 
I should have clarified it. The corrosion is at the end that plugs into the old pmd. The other end of that cable is butt-spliced at it’s connection (the pink wire is broken). I am seeing a harness online that appears to be this connection point, with a black wire ending in a terminal lug. At the other end of it is a harness connector, plus a red & a black wire each with a terminal lug. I assume all of these hook into the IP. How hard is it to replace this harness?
 

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It looks like it’s going to be a real pain to replace that harness. So, I cut the butt splice and soldered on spade connectors from the old harness to the harness that goes to the old PMD. It did not make it run any better or worse. Now I have to splice in a spade connector on my new PMD wiring harness so that I can use it.
 
Ray2377 said:
It looks like it’s going to be a real pain to replace that harness. So, I cut the butt splice and soldered on spade connectors from the old harness to the harness that goes to the old PMD. It did not make it run any better or worse. Now I have to splice in a spade connector on my new PMD wiring harness so that I can use it.
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As one of the few to trash a diesel from a worm clamp on the IP return line falling into a head intake ports I can't disagree on risk. However it's 16 bolts and misc other bolts to pull the manifold. The injector line clamps are the PIA part. I suggest replace that small harness. If you're real good: I have removed the FFM and replaced the IP hose on DB2 pumps with intake in place. Maybe you could do same on DS4 with the two screw connectors on the nose of the IP?

Others on here tell you PMD and PMD wires being iffy... Is PMD related. You got to eliminate the wires. One broken wire already, frankly, why are the other old wires any better? Just saying replacement is best option. The engine harness connection is also suspect. I Forgot who on here cleaned up theirs to fix it.

If you need proof: there is an extensive DS4 trouble shooting guide in the technical reference section hidden as Cal resistors. We also have a hunting and firearm section if you really need to troubleSHOOT it. :woot:
 
I think that I am going to let it ride like that for a while. I still want to get it popping and swap out the pmd’s to see if it helps. I am still curious as to why the current pmd has no resistor and why it runs without one?
 
Ray2377 said:
I think that I am going to let it ride like that for a while. I still want to get it popping and swap out the pmd’s to see if it helps. I am still curious as to why the current pmd has no resistor and why it runs without one?
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IIRC the PCM remembers the last resistor value, I don't know for how long>
 
It’s amazing how frustrating not getting a problem can be. I haven’t had the popping issue in the last half a dozen times I’ve driven it to include today when I pulled my tractor behind it. All I wanna do now is get it to happen and then pop the new PMD in to see if it changes anything. Because I know it’s going to come back. Unless it’s the cold temperatures that are keeping the old PMD cool enough not to have problems.
 
You fixed some wiring. I suggest that may have been it. Or you wiggled wires and connections so it connects now... till the corrosion comes back.
 
It finally started the popping again while I was hauling my tractor. I plugged the new pmd in, without mounting it to the new heat sink. No popping. Drove it 30 miles with no issues and then plugged the old one back in, started popping right away. However, the new pmd was very hot already. I let it cool down and mounted it, on the heat sink, in the bumper. It did not “pop” that day. Hopefully it is fixed! Exhaust is next item on list when I can afford the downtime.
 

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Good news is ya found your problem and got lucky you didn’t burn up the new pmd. They really need a means of shedding the heat.
Bad news is ya probably took some of the life out of the new one doing that.

Thats why I am such a proponent of mounting the spare right near the other one. Then plug in a dummy plug to keep the connection clean. When things go wrong and it dies totally, might be middle the night on a bad road. Then you can always swap the old dead one in for warranty when comfortable.
 
Good to know You got it all figured out.
If it were not for the PMDs burning out and causing problems with these engines, they would be very dependable and run a very long time without any work to do to them.
 
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