PMD problems

[nextlevel]

I have a 1995 c2500 6.5L. I have replaced the PMD 3 times in the past 3 years. Is there another solution for this part? It is very expensive.

James

[Robyn]

The best solution we have to date is to mount the PMD on a good remote mounted cooler outside of the engine bay.
Extention cables available from various aftermarket sources up to 6 ft long.

Dtech now offers a replacement PMD for a fairly decent price. I paid $279 for mine IIRC
I installed one of these on my 95 DaHooooley earlier this fall when I was having some issues with it. Turned out to be another little problem but there were no codes and anytime the engine cuts out the PMD can be a suspect as far as Im concerned, at least when other obvious things are eliminated first.

The DTECH PMD looks just like a factory unit except it is a little thicker.
The key is remote mount it where it stays cool/Cooler than under the hood..

Another issue can possibly be poor grounds on the battery cables as well as the psitive cables too. An alternator thats starting to toss alternating current rather than DC can louse things up too.
Be sure your engine and body grounds at the rear of the engine Intake manifold RH side are clean and tight.

14v+ should be seen at the power box feed with the engine idleing.

The sensitive micro electronics on these trucks needs to see good clean voltage.
If the cables are going south and the voltage is dropping off then the amperage draws can climb. If there are ground issues this can seriously effect the electronics as when the grounds go sour all sorts of wierd crap can happen including damaging sensitive circuits.

Another seldom taked about subject is that whenever a rig has some welding done on it, such as a hitch or ???? the batteries should be disconnected.

Check these things out as well as remote your PMD

Hope this answers your ?????????

Happy Hollidays

Robyn

[CapnAmerica]

This subject always stirs up comment...

I bought a 4-foot extension with finned cooler, removed the cover over the power transistors, used Bellville-spring washers (supplied by that vendor) to mount PMD to cooler, used the supplied heat-transfer goop, and moved the PMD to the bracket with the ABS controller on it--handy threaded holes there :). Then I had another failure :(. This time I moved the whole thing to the hole in front of the driver-side battery, and mounted a fan in front of it.

To date, no failures! :);):D:p

Info on the fan: Radio Shack item #002763154, 120x25 mm...still running at last check. It was a trial to check life, because this is quite a bit more severe duty than sitting in a case on the floor of the house! I have the fan running at high speed (it's adjustable) whenever the ignition is on.

Good points, Robyn, on the voltage, and on welding. I would go a notch more conservative on welding issues, though, because in my former life as a maintenance manager, I saw some suspicious things happen on equipment on which we welded. The stray and induced currents on the structure being welded aren't at all predictable, and damage can occur which goes undetected while allowing function of the part, but later causes a "mysterious" failure. So I would unplug the PMD when welding is being done...come to think of it, maybe one of MY failures happened after I welded up my 4" exhaust:eek:!!!

Also, get rid of the side-post batteries...they will at some point, if you keep the truck long enough, seep acid through the internal seal and make your connectors disappear while never showing any problem outside the little plastic cover. (It's nice to be able to make a firm connection if you want to jump another vehicle from...or TO...yours.)

AND...don't forget to remove the %*&$^*@ TURBO POWER plastic cover, even if you also move the PMD. Trapping the heat and inhibiting air movement ANYWHERE around the injection pump can't be good for the fuel-supplied lubrication of the injection pump. (Not to mention its former duty in trapping heat to help roast the PMD!?!?!?)

¡Buena suerte! Good luck!

[Robyn]

YUPPPPPPPPPP as far from the heavy heat as is possible.

The PMD is not nearly as vulnerable to the stray currents as is the Computer/ ECM-PCM

Disconnecting the battery cables will "Usually" stop any issues as there is not a completed path for the flow of these stray voltages.

If the gounds are not connected then in theory there would be no path for the influx of current.

The class 8 trucks have stickers all over them as to this very subject due to the many and varied upfits this stuff sees when being outfited to do specific jobs (Dump trucks, cranes ect)


The removal of heat from the PMD is the one proven thing that does enhance the little black box's life span.

I am very excited to now see that there is another player in the PMD arena.
With Dtech making a replacement we at least have a somewhat lesser expensive choice.
I am running one now so we shall see.

I run the dual post Optima jello batteries and have had very good luck with them to date on all my rigs.

The big truck gets top threaded terminal commercial batteries and they are ok.

Yup the cables just go away inside and still look great :(

Been mugged there a few times earlier in my life. :eek:


best
Robyn

[Jim Faire]

Personally, I figure if your truck has eaten 3 PMDs in 3 years, you should be thinking about buying one with a warranty.

The Heath PMD Isolator (reviewed on this forum) has a 7-yr warranty and mounts outside the engine bay.

Half of the issues with home-brew solutions include wiring, flat surfacing on the heat-sinks, improper thermal transfer application, poor electrical work or grounding issues, and finally not doing the calculations on mass/suirface area of the heat sink for thermal balance.

Why tell somebody that's already bought 3 PMDs to try again?

It's not like the worst that will happen is it might not start... stalling in traffic with a load on is scary (steering/brakes/hydroboost), or when merging, or just plain dying out in the boonies somewhere (it IS winter, ya know). Peace of mind is priceless.

Phone Heath Diesel or USDieselparts and solve your problem for 7 years.

JMHO

[Robyn]

I have seen several failures of electrical stuff after rigs have been to the exhaust shops.

All it takes is a little wild and wooly fluxing of current induced into some little electronic component to set the failure in motion.

An old friend of mine installed hitches for years and did a job on a Reeeeeeeeeealy high $$$$ Mercedes and after he finished the hitch the rig would not run :eek:

He called me and I advised him to disconnect ther batteries and wait about 10 minutes and then hook it back up.
Seems that the Mercedes has some sort of circuit protection system????

It ran fine afterwards and the rig was a local one.

Enough to make one shudder though at the thought.

Robyn

[Jim Faire]

More likely, it was the RF flux affecting the Engine Immobilization system, Robyn. They can be re-set with a battery disconnect, too.

It's highly unlikely that you're gonna damage electronic components with EM flux - unless you attach a ground clamp to the electronics, rather than the frame or exhaust pipe.

[Iain]

Definity re-mount it away from teh pump to a better, more cooler spot. The mounting on the pump is a heat trap. I had my pump changed on warrenty (3rd one) just prior to the warrenty expiring (193,000 km I believe it is). I remounted the PMD and now have 350,000 km on this last pump with only one change of the PMD. The old one was still good but I am a cautious fella and wanted a good used spare anyways!

I know I will get some arguement back on this, but I did mount mine on top of the intake with an FSD Cooler. I realize this is not the best spot, but as the colder weather up here helps keep the engine temp down and the Duramax fan I use seems to pull a lot of air over the engine, it works for me! As well, I do very limited towing so I do not pull the heavy loads that other members do.

My 2 cents or so......
Iain

[Jim Faire]

I'm not gonna argue with you, Iain, but since I've been stuck on Deerfoot or Macleod before too, how about you try this:

Get yerself one of those remote-mount bbq thermometers at Canadian Tire. Put the probe under the hood, say, next to the PMD. Put the readout inside the cab.
http://www.canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=84552444329 4732&FOLDER%3C%3Efolder_id=1408474396672586&bmUID=1200340522155&deptid=1408474396672561&ctgrid=1408474396672562&subctgrid=1408474396672586

Next time you find yourself sitting still on a 90*F Calgary day, check the thermometer. Your DMax fan doesn't help too much with that, and after you shut ioff the truck, the temp will continue to climb for about half an hour. It's called 'Heat Soak', and having cold winters doesn't fix that in the summer.

If you're surprised by the temperature you find, try different places under the hood... you might be surprised to find that mounting it above the intake manifold is just about the hottest spot in the engine compartment.

Sure am glad it's working out for you so far, though! PMDs are a pain in the butt.

There. My .02+gst.
Jim

Definity re-mount it away from teh pump to a better, more cooler spot. The mounting on the pump is a heat trap. I had my pump changed on warrenty (3rd one) just prior to the warrenty expiring (193,000 km I believe it is). I remounted the PMD and now have 350,000 km on this last pump with only one change of the PMD. The old one was still good but I am a cautious fella and wanted a good used spare anyways!

I know I will get some arguement back on this, but I did mount mine on top of the intake with an FSD Cooler. I realize this is not the best spot, but as the colder weather up here helps keep the engine temp down and the Duramax fan I use seems to pull a lot of air over the engine, it works for me! As well, I do very limited towing so I do not pull the heavy loads that other members do.

My 2 cents or so......
Iain

[Iain]

Hmmm, good point Jim. Seeing as you am from Calgary as well, where did you mount yours? I do drive in the bush some so I want it out of the snow and mud.
Iain

[Robyn]

Mount the little beast out front in the grill area so it has cool (ambient) air.

I have the one on my Burb mounted on the top side of the front splash pan right under the radiator.

Easy to get to and well protected. JK likes the hole behind the LH battery. I have seen these mounted on the winch bumpers out front in a protected spot.

Just get it to a cool place and it will certainly help

Robyn

[Jim Faire]

Hmmm, good point Jim. Seeing as you am from Calgary as well, where did you mount yours? I do drive in the bush some so I want it out of the snow and mud.
Iain

Mine is up behind the bumper... I asked Bill Heath about that, and if it would affect the warranty, he said no, so that's where I put it.

I know some guys that have them behind the grille, or inside the bumper, or behind the winch... one guy that put his behind the license plate. Like Robyn says, anyplace out of the engine compartment is a good place.

The Heath ones are all weather-sealed... and warrantied for 7 yrs. I remember hearing about a test on one that ran it submerged in 5-gallon pail of water. I get in the slop a fair bit, and mine has never burped...

[rbr]

Hi all,
I need a new PMd and want a remote, seems there was a less expensive one around a while back that someone was testing but I haven't seen anything lately. Also wondering if ther is a better oil cooler hose than Dorman or GM. Ihate leaks and am on my 3rd set.
Thanks, great site Jim!

[Robyn]

DTECH is offering a replacement PMD now that seems to be a winner.
DEPACO is the seller.

Good luck

Robyn