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6.5 “pops” & blows black smoke intermittently

Ray2377

1997 K3500 Flatbed Farm Truck
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This is a carryover from a previous thread that got really long. I have a1997 K3500 and just got the glow plugs fixed, so I can start it in weather under 60 degrees. As I stated before this problem is intermittent. Sometimes just after idling, and sometimes when I’m driving down the road. What happens is that I step on the accelerator to rev it up and when I let off it will pop and blow Black smoke until the RPMs drift down to about 1500 or less and then like a switch it immediately smoothes out and drop down to 900 rpm’s or so on the coast. If it does it when I’ve just had it idling in the driveway, it will do it in park or neutral but as soon as I shift it into gear the popping immediately stops. I hauled a trailer and old truck with it yesterday for about 50 miles and it did it the entire way, also puffing out black smoke during acceleration. Then I drove back without the trailer and it did not pop once. I put in a new air filter & opened the front T valve with no stalling out. I am stumped.
 

Will L.

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I will leave komputrz plugged in and readings to those who are better than I on ds4 possiblities.

My big concern would be some unhappy valve springs in there. Chase the easy stuff first, but keep this as a possibility if the ds gurus cant fix you.
 

WarWagon

Well it hits on 7 of 8...
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Take a look at the videos in this thread of mine. Bad bent valves, weak springs, and busted spring. And some other iffy things. But is this the popping?

 

Ray2377

1997 K3500 Flatbed Farm Truck
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I watched the video and am not sure that’s the same noise. The fact that it is hit or miss makes it tough. There is no load after idling and then accelerating while in park. And there is a definite load doing up to 90 mph on the freeway and it did not do it. The randomness almost makes me feel like it’s intermittent electrical, but I have severe lack of knowledge on diesels. As for the OS, I assume that’s the optical sensor. I don’t know what the CPS is. In both cases, I am not sure how to troubleshoot them. Could a failing PMD do this? The one on it has been moved and put on a heat sink behind the battery on the driver’s side. It has never had dying issues.
 

ak diesel driver

6.5 driver
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CPS is crank position sensor to test you unplug one of them and then start the engine. It will take extended cranking to get it to start and will be in limp mode. If it runs smoothly then that sensor is fine, turn it off and plug that sensor back in and repeat the same procedure for the other sensor. PMD can have other issues besides dying/stalling. Only real way to test is with a known good one, make sure it has a resistor in the PMD where the cable plugs into it.
 

Ray2377

1997 K3500 Flatbed Farm Truck
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Are the crank position sensor and the camshaft position sensor the same thing
 

Ray2377

1997 K3500 Flatbed Farm Truck
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I forgot to have it scanned for codes. I will try to do that this weekend.
 

Ray2377

1997 K3500 Flatbed Farm Truck
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I was just looking for a spare pmd. Stanadyne only, or have there been some successful aftermarkets?
 

ak diesel driver

6.5 driver
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None of them I'd call successful. Flight systems makes most of the after market ones, D Tech being the most notable. There are some cheap Chinese ones now too.
 

Will L.

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Just get lifetime ones, anything else is a mistake imo. Mount two next to each other on heatsinks and use a dummy plug filled with silicone (let it dry before installing) on the old one and run the lifetime one. When it dies use the old one while waiting for shipping of new one.
 

Ray2377

1997 K3500 Flatbed Farm Truck
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Leave the spare in the engine compartment? Heat over time?
 

Will L.

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Getting them mounted down on the back of the bumper in trucks/vans or opposite the batteries in Hummer so that it is completely away from engine heat is a key.

But yes,mounted spare. In the fleet we always had a spare mounted right next to he one in operation. Taught the drivers to just move the plug over and get back on the road. Then just call it into dispatch their truck number and what they did. Had them sharpie the date onto the new pmd. Back then we had the pmds both mounted on 1 large heatsink and in the cab. No passengers, so it wasn’t in the way of anyone. We learned that wasn’t best in winter because drivers would have the heat on blast.

Having the spare mounted is also safer. Think when the truck dies on the freeway or busy road. Maybe summer heat of day or freezing winter storm. You want to be out there for 15 minutes swapping pmd or take 10 seconds to unplug a dummy plug and mive over the wire, then get in and go...
 

Ray2377

1997 K3500 Flatbed Farm Truck
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That makes sense. I will have to scope out the bumper area. My bumper has some “nature made” air passages.
 

Ray2377

1997 K3500 Flatbed Farm Truck
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I just saw a Dorman PMD setup with 6’ cable for $170 and it says lifetime warranty.
 
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