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Thread: Question about replacing the PMD

  1. #1
    Join Date
    Sep 2007
    Posts
    354

    Default Question about replacing the PMD

    Thanks to this forum, I relocated the PMD and heat sink to the bumper hole years ago and, after Grancito told me how to install a manual switch for the fuel pump, I have been driving worry-free for a long time. But yesterday, the truck repeatedly started up right away then cut off after 5-10 seconds. I tightened the four PMD screws and drove home without a problem.

    Now I am wondering, about how long before PMDs need replacing and how do I know when they are starting to go bad?

    Thanks for any advice.
    1997 Silverado 1500 6.5. with 200,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016. New Interstate batteries 4/13/19.

  2. #2
    Join Date
    Feb 2007
    Posts
    2,891

    Default

    I hear that they usually suddenly die, and will sometimes work for a short distance after cooling down. But those were in the original place on the IP, A code either 35 or 36, can't remember which, can indicate a failing PMD. They last like other electronic devices, could be 50 years or 1 year. The one in my suburban was fitted in the bumper in 2006, and the one in the truck, in 2015, and haven't failed.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

  3. #3
    Join Date
    Sep 2007
    Posts
    354

    Default

    Thanks for the info. I guess I'll just keep a spare in the truck.
    1997 Silverado 1500 6.5. with 200,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016. New Interstate batteries 4/13/19.

  4. #4
    Join Date
    Feb 2007
    Posts
    2,891

    Default

    I have a spare in each vehicle and a spare alternator regulator in the suburban, the regulator was failing every 5,000 miles. The alternator has to have some holes drilled in the internal plastic guard, and some solder on wires changed to plug on, to be able to disassemble it on the side of the road.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

  5. #5
    Join Date
    Sep 2007
    Posts
    354

    Default

    I've never had a problem with the alternator regulator, but I'll keep that in mind, thanks.
    1997 Silverado 1500 6.5. with 200,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016. New Interstate batteries 4/13/19.

  6. #6
    Join Date
    Sep 2007
    Posts
    354

    Default

    It's been running well for the past 5 months, except for replacing the starter bolts after some past mechanic left off the starter brace. Then last week it cut of twice within a half mile of my house. Thankfully, I made it back up the hill to my driveway and took the Subaru to work. If it ever stops raining, I am going to check the pmd screws again. If they are already tight, I'll put the other pmd on and order a new backup to keep in the truck.
    1997 Silverado 1500 6.5. with 200,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016. New Interstate batteries 4/13/19.

  7. #7
    Join Date
    Feb 2007
    Posts
    2,891

    Default

    Remember that the ignition switches on the 95 and later fail and cause intermittent problems with various electrical functions. Mine caused no transmission shift, lots of solenoid codes, and on one occasion, low battery voltage/charge voltage. The next day it had no shifts, I parked at the airport and took the ECM to the other side of the world, where no one could test it. I returned 9 days later and put the ECM back in and the truck had gear shifts again.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

  8. #8
    Join Date
    Sep 2007
    Posts
    354

    Default

    I replaced the Ignition switch a few years back but It has been sticking in the forward position off-and-on over the past 6-8 months.I replaced the 6-foot $25 PMD harness and it still cut off a couple times yesterday when I 1st started it up. I'll go ahead and replace it before I replace the PMD again.
    1997 Silverado 1500 6.5. with 200,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016. New Interstate batteries 4/13/19.

  9. #9
    Join Date
    Feb 2007
    Posts
    2,891

    Default

    The extension plugs could cause a problem if you have salt roads. If the problem happens a lot, jump the IGN fuse to the live post behind the fuse box, to see if the problem stops, that will tell you if the switch has failed again. You have to disconnect the wire to stop the engine. People have many other problems from bad mechanic work, wire insulation warn on the cables under the manifold, missing engine to body ground at the back of the engine.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, 3.73 diff, 16 mpg
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, since 1992.

  10. #10
    Join Date
    Sep 2007
    Posts
    354

    Default

    I have a older pmd that might still be good. I replaced it and the 6 foot extension harness before I knew that the harness could be the problem. I'm going to give it a try but I don't have a pink pad to go in between the pmd and the metal cooler. What's the name/type of goop or grease that I can use in place of the pink pad? Also, is the grease or the pad better to use? Thanks.
    1997 Silverado 1500 6.5. with 200,000 miles. New fuel injection pump at 132,000 mi. FSD Heat-Sync in bumper hole, marine fuel injectors, air induction kit all from Walt at 148,000 mi. Replaced OEM Fuel Filter Assy, wastegate solenoid valve, OPS and relay at 155,000 mi. Harmonic Balancer replaced. Red dot and White dot EGR replaced. New starter, Instant Heat glow plugs, and glow plug relay/controller at 180,000. Replaced hydroboost and master cylinder in 2016. New Interstate batteries 4/13/19.

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