You are not going to get much responce in the performance section, maybe the mods can move it, but it sounds like a PMD issue, I bought a new PMD that did that, I exchanged it and that one did the same thing, I found out that the flight systems ( diapco, Dorman etc...) were having issues so I got a Stanadyne PMD and has worked since, have you changed the PMD or IP lately? The PMD on the side of the pump is bad it needs to be moved to the bumper, look at pmdcable.com or heath for an extension harness and new PMD, I would try a good known working PMD first, and then keep a spare in the glove box!

 

Check the name on the pmd, if it is anything other than stanadyne, such as flight systems, then I would start there, fs had a bad batch of pmds that when they failed they would go into full throttle mode. Already had it on my truck, bought a new pmd and an extension harness and mounted it to my front bumper. Haven't had a problem since then.

 

Just checked out the PMD. It is a Dtech made in the USA. Could this be the issue? It is mounted on the far right hand sideabove the front tire well and has a fan attached to an aluminum heat dispensing metal bar. It seems to be in a good location although not on the front bumper. Would you recommend a Stanadyne or is Dtech a better unit?

Apparently, Dtech hired Flight Systems to manufacture these PMDs. Based on what you have said, the DTech (FS) may be the issue.

Aside from the PMD, what other issues may cause runaway acceleration? It does sound like a computer issue vs a hardware issue. Thanks!

 

I would still mount it in the bumper, and yes Dtech is a flight systems PMD, look at a kit that comes with the PMD, cooler and extension harness( not from ebay) find a reputable seller, Heath or pmdcable or Kennedy diesel as mentioned before.

 

Thanks for the insight! I will order a new PMD and will keep you posted on the outcome. Once installed, I should know within a weeks time if it is working correctly. I will re-run it to the front pumper or around that area.

 

The PMD is the only logical explanation for those symptoms. How its supposed to work. PCM receives input from 3 sensors in the fuel pedal. If any one of them is actiing up the other two check it and cancel it out and you get a code for it. The PCM then looks up a fuel rate by pedal percentage and RPM and translates that into a pulse width to the PMD. The PMD takes that pulse width and spits it out in a higher voltage and current signal to the IP's fuel solenoid. The fuel solenoid reacts to the power by closing the metering valve which allows fuel to be pushed to the injector. Then the pulse goes away (to zero power) and the valve opens and repeats the process over and over.

The PMD is the middle man in the equation, and can often times go rogue. The PCM would control itself or any of its inputs and outputs.

 

Interesting! Thus far the majority rule is the PMD. I say interesting because, Heathdiesel dot com says it's the Injection Pump and my mechanic says the same. I am hoping that a lot of people in my same situation can benefit from this thread. Will keep you all posted!

 

Well, funny story, i was told the same thing when my truck acted, same as many people here have, but I decided to just try the pmd for shits and giggles because the IP on mine had less than 5k on it. And if it was the IP you would have zero control over it at all. When the armature shaft (iirc) breaks you basically have 2 pedal positions if your lucky, off or full throttle... I highly recommend replacing the pmd for starters and moving it to the bumper. I bolted mine to one of the valance holes in the bottom flange of the bumper and drilled a second hole for the other bolt.

 

I thought D-Tech was supposed to be the best available? With heat soak and all... So stanadine(?) is the best choice?

 

d-dech is a rebadged flight systems pmd which is the most common to have the runaway when failing, stanadyne generally just dies when it fails but there have been a few reports of those as well having the sudden acceleration but are far far less common to do so.

bottom line is both stanadyne and flight sytems(which anything not labeled stanadyne is made by) both fail at any time, the stanadyne is the least likely to have the runaway happen but its something that every electric 6.5 owner should always be prepared for and if you are experiencing any random surging it is more probable it will die on you soon.

 

Moved to 6.5 Engine section

 

Well that sucks. And false advertising too.

 

What do you mean false advertising thier name is " Flight Syatems" they tell you in the name they will run away!

 

Technically, if you get one of these Flight Systems PMDs you can get a free replacement. Just give them the serial number and I think they even published a range of serial numbers that are suspect and can be replaced outright.

And since then they have done work to address the issue, so that their latest model is likely the best PMD available. Their competition also pushed Stanadyne to actually try to address the common failure item. And drove the price down, so wouldnt crucify them just yet.

 

My Dtech has lived happily on the intake for more than 4 years now. So it can withstand high temps. I had two thermistors installed, one on PMD heatsink at base of PMD and another on the IP where PMD used to be installed.

The PMD heatsink would usually be around 130F, up to as high as 150F sometimes. My DMax fan that pushes more air without clutch engagement may have been keeping the whole intake cooler than stock fans. The IP was always about 20F higher under the intake.

 

you were lucky it lasted that long
its not temps while running that is the issue, its heat soak after the engine is shut down that kills them, your fan pushes no more air than the 97+ fans, its just plastic vs the steel, same diameter and blade count

 

I know why they fail, its just people always go back to heat being the issue, and its not really. I have driven it through death valley, and Nevada, to Las Vegas several times. In general though, yes I live in temperate climate, and thats where its operated the most.

And yes, the DMax fan does pull more air than a stock 97+ steel fan. Its about the blade pitch and surface area, and design.

And you know what, I have monitored the temps after shutdown, never skyrocketed, maybe a couple of degrees higher. I monitored the PMD temps for over a year, on a battery operated unit so it was at all times, cold, hot, running or not.

 

It is the fluctuating temperature is the main cause and exposure to an extended length of hot.

I don't have thermocouple in mine but one summer I just measure temperature under hood. It goes all the way up to 230F -240F after shutdown with an open hood from 200F initially. So, I am not sure if it is skyrocket or not. It is all relative.

We have days over 100-110 F here in North Texas, sometimes more than 30-40 days in a summer. Bet you never happened in California.
You probably drove through Death Valley once in a while but not everyday but the engine was not shut at that time and keep running.
I did that 26 yrs ago, it was hot.

I just have stock fan.

 

We actually have a good number of days/weeks of 100F in CA, in a lot of CA. I live near the coast where they are limited, only about one to two weeks out of the year for me and the rest in the 70/80s, but go inland 25 miles or more and its basically a desert most places, some of the hottest in the US.

You need to measure actual metal temperature to get something meaningful, the stagnant air might be hot from the exhaust manifolds, but do you fire up the engine and the temps are 230F? Not really.

I have monitored the metal temps after shutdown without opening the hood, my temp readouts were on the dash to watch at all times for over a year. It was driving through the desert areas and the 100F weeks that I observed the high operating temps of ~155F, on the metal heatsink part, when coolant temps might hit 210F on the scanner and gauge. The internals of the PMD might be hotter. Thats the temperature of the PMDs heatsink bolted to an Aluminum heatsink bolted to the Aluminum intake. If the PMD is on the fender wall it should absorb less heat just from air transfer. In the bumper allows less thermal cycling, as its always as cool as it can be. Even though, I have no doubt any PMD could run just fine at 180F for years if you never brought it down below 80F.

I think you will have more failures in or from the the winter (could fail later but most degredation happening in winter), when you get the PMD below freezing and then run them up to 150F, day in and day out 100+ degree swings. I never get mine to freezing, or even close really, so it doesnt care that its hot, 140F max most days, and I verified the thermistor readout with an IR probe several times.

I also had an original Stanadyne that was on the IP for the 6 years at least that the PO had it, partly in NJ, then CA. It still works, its my spare. I think some trucks also eat them more from other factors as well.

 

The reason I joked about false advertising was, IIRC, I thought I read in their add in one of the first Maxx-Tourqe magazines, was their improved heat resilience.

I wasn't crusifying them, just poking with a big stick LOL