PMD relocate, rain, sudden acceleration

[Coal Roller]

Ive had a new pump and PMD installed on my 97 ck-2500 pu at the beginning of this year. I had the installer mount the pmd, on a cooler on top of the intake, but still found the unit gets very hot to the touch. I was concerned about this even though "they" say that the new units are built more rugged. The hood on this truck is insulated and in the summer it gets ferociously hot under there when the truck has been parked after driving.

I decided this fall to pick up an cable extension to mount it near the bumper, well the only place i could find a space was just below the bumper as it is a very cramped area to put anything. There was a hole punched at the bottom of the bumper that was a very convenient mounting point, so that's where I put it, and what a difference. The thing stayed ice cold and I think the truck ran smoother. Well that was in the fall and we have had little rain.

Yesterday I was driving home in a down pour, following traffic and all of a sudden the truck starts jumping in and out of full acceleration mode, then it locked into full throttle. I had to apply hard braking to stop it ploughing into the traffic ahead, I turn off the key and coasted to the side of the road and could see a huge black cloud that got pumped out of the tailpipe. After about thirty seconds I cranked it back up and it instantly wound past 3000 rpm and belched out black smoke.

The trucks never done anything like that except for a few jumps just before I had a new pump installed, so i started to think that the pmd was getting sprayed with road mist and causing signal problems going to and from the PMD. Well the Pmd was getting wet, so I unplugged it and wiped it down with a napkin and plugged it back in and so far its been running fine again.

Today I relocated the PMD back into the engine compartment, but away from the engine where there will be no chance of encountering moisture.

It makes me think that many of the problems I read about on here with erratic throttle and smoke is directly related to communication problems between the pump and the pmd, be it with the wiring harness, grounds or the unit itself.

So far Ive been happy with the 6.5 Unlike the horrific stories Ive been watching on Youtube about the power strokes, the 6.5 is simple and the parts are frigging cheap in comparison.

PS This forum system is irritating. I'm logged in all ready wtf do I need to input the image verification after previewing the damned post.

[trbankii]

my 97 ck-2500 pu

C=2WD
K=4WD

No such thing as a CK


PS This forum system is irritating. I'm logged in all ready wtf do I need to input the image verification after previewing the damned post.

The extra confirmation is for new members of the forum to make sure they’re not spambots. Once you have a few posts under your belt the extra stuff will disappear.

Relocating the PMD away from heat is a good thing, but I’m going to guess that the issue was not the PMD getting wet, but the connection of the cable TO the PMD getting wet. Unless that is sealed well, water inside the connection will cause all sorts of trouble.

[Robyn]

Ok

To address the issues.

The best place/s to mount the pmd are

Under the aluminum guard plate below the radiator
Behind the bumper (Access through one of the nostrils in the bumper)

Keep the unit out of direct contact with heavy water.

The full throttle event is the second and least common failure type of the PMD

The most common failure is the stall and no start when hot or stall and no start at all.

In the many years I have been around the 6.5 I have only seen a few of these "full throttle" failures

Replace the PMD with a fresh one and get it in a cool and relatively dry place.

Even with the remote mount on the PMD it is advisable to carry a spare in the rig.

The PMD is a "consumable" item and there is no perfect long term solution.
Some will function a long time and others will not.

Good luck and happy to hear you did not incur any issues due to the "Runaway" other than inconvenience.

[a5150nut]

Clean all electrical connections with contact cleaner and apply liberal amounts of dielectric grease.

[Coal Roller]

C=2WD
K=4WD

No such thing as a CK



The extra confirmation is for new members of the forum to make sure they’re not spambots. Once you have a few posts under your belt the extra stuff will disappear.

Relocating the PMD away from heat is a good thing, but I’m going to guess that the issue was not the PMD getting wet, but the connection of the cable TO the PMD getting wet. Unless that is sealed well, water inside the connection will cause all sorts of trouble.

Sorry , I was going to edit that with a few other things but got tired if figuring out some of the characters in the image. Anyway. Thank you for the info about the security protocol.

My truck is a k-2500 4x4. I can best describe the episode as, the truck went bonkers, It like dies for a second then did intense surges, belching enormous amounts of black smoke out the pipe, Then just started to accelerate like a jack rabbit. It was like the pump went into overdrive and delivered a maximum flow of fuel to the injectors at a rate far exceeding the capacity for the engine to burn it.

Ive now put the PMD behind the drivers side battery on a existing bracket plate above the abs module and have driven 1200 miles without any further problem and it stays cool there.

Btw on a recent 600 mile trip I calculated the mileage at 16.7 MPG using cruise at 60 in mountainous terrain. I see that others claim much higher for their 6.5's, but that seems a reasonable figure for a truck that weighs in at close to 7000 lbs.
Thanks to everyone for their comments.

[a5150nut]

Coal Roller

16/17 mpg is what I averaged with my 94 K2500 5 speed and 285's

There is an opening in the bulkhead just in front of the drivers side battery where you get a nice flow of ambient air over the PMD. One hole for your two bolts is already there.

[phantom309]

bigger tires,. you go further, but the odometer reads less,. so it seems like worse fuel mileage with bigger tires,.

[jrsavoie]

C=2WD
K=4WD

No such thing as a CK



The extra confirmation is for new members of the forum to make sure they’re not spambots. Once you have a few posts under your belt the extra stuff will disappear.

Relocating the PMD away from heat is a good thing, but I’m going to guess that the issue was not the PMD getting wet, but the connection of the cable TO the PMD getting wet. Unless that is sealed well, water inside the connection will cause all sorts of trouble.

And yet the titles on 2 of my trucks say C/K 3500 or whatever on them.

The confusion is understandable.

I have been replacing the engine harnesses on my old 6.5's as I work on them. My harnesses are all a little worse for wear.