Thursday, October 20, 2011

Pump Mounted Driver (PMD) FSD Heat Sync Fix and Upgrade

It's been a long time since I haven't wrote about my big red GMC Suburban Diesel but that's mainly due because in the summer months, there is no real use to having an off-road monster. Here up in Canada, especially far from the city, a good 4X4 truck is very useful in the winter. With temperatures going in the -25°C or -13°F here in Quebec (Canada) without the windchill factor, the factory GMC Suburban will not start if not plugged in and with no diesel additives. However, this post in not about starting a running the truck in the cold, it's about fixing the most common issue with the 6.5 V8 Turbo Diesel engine. Unless it's always below 0°C when you run your truck, overheating the Pump Mounter Driver (PMD) is not a IF but a WHEN. My WHEN happened this summer when I has hauling my Mazda MX3 KLZE in a forest trying to place it for winter storage. Since I wasn't going forward very fast and it was somewhat a hot day, my PMD eventually overheated. A combination of really poor location in the engine and the fact that cooling the two 500 watt transistors in the PMD is done by your Diesel fuel passing in the injection pump finally killed it. By the way how stupid is using diesel to cool engine parts. Since, diesel is in a closed loop and uncooled system, eventually your diesel will heat to a point which it doesn't cool the PMD anymore and has no effect. The fact of running on a low fuel tank also makes this worse.

What the hell is a Pump Mounter Driver (PMD) or also called Fuel System Driver (FSD)?
I find that understanding is the key to fixing anything. If someone tells you do this, you ask why, as the next time this happens you might not have the luck of having mister know-it-all to tell you what to do. The PMD and FSD are the same thing, with just two different names. From now on in the post I'll use PMD not to mix people up. So the PMD is a small black box bolted on the side of your electronic injection pump. It is the size of a deck of cards. The PMD relays the information from your engine computer to your injection pump. It tells the injection pump when to give fuel to which injector. That's why when it stops working your engine just shuts off, it because the PMD stops telling the injection pump to give fuel so it's the same thing as turning off your ignition key. On a side note if you were to run a switch on the PMD, you could stop anybody from starting your truck unless they turned on your hidden switch. The truck will crank but since it's not getting any fuel, it would never start. A neat little future project not to get my Suburban stolen...

The Ultimate Fix for PMD Failures:
The best fix for PMD failures is to relocate the PMD from the intense heat of being strapped to an injector pump in the middle of the engine bay and into a higher up, cooler spot with some sort of better cooling mechanism. A huge aluminium heat sync proves to be a very good fix for the problem. The radiator fans sucks cool air in the engine bay which cools the heat sync and the PMD. There are a number of places you can buy a new improved PMD and Heat Sync combo. Two of the most popular ones that proved that their products work are Accurate Diesel and SS Diesel Supply. They both sell their FSD Heat-Sync for 350$US which includes a new heavy-duty PMD, special oversized heat sync, and #9 resistor. The sell the exact same product from the research I have done, so it's no importance from where you get it. I bought mine from Accurate Diesel only because they also sell on eBay and I was using an eBay certificate to pay for a part of the item. I recommend changing everything at once and not salvaging your existing PMD and bolting it on to your new heat sync. The reason is that your old PMD may already be defective or even worse, might have been damaged but it is not yet noticeable. The other reason is that removing the PMD requires removing the intake manifold which is very long to do. Even if your PMD is broken just leave it where it is, you only have to disconnect and connect your new PMD. Moreover, if you PMD is not 100% dead, meaning that engine doesn't start at all anymore, keeping it might be very useful. In the event that your new PMD breaks, you can simply reconnect the old one and you can bring your truck home without calling a towing... In the next section I'll go into an in-depth explanation on how to change the PMD. Instructions are included when you purchase you PMD from the two sources indicated above but I like to include mine because the coat-hanger trick did not work for me and I had to remove the upper intake manifold. My how-to, includes the removal of the intake manifold, which is pretty easy and you can give it a good clean while being there...

What You'll Need for the Upgrade:

  • A complete FSD Heat-Sync kit
  • An upper intake manifold gasket
  • Your trusty socket wrench and adapters
  • An 8mm socket
  • An 10mm socket
  • An 13mm socket
  • An 19mm deep socket
  • A T25 Torks (Star Key) bit
  • Phillips Screwdriver


Step 1:
Disconnect both the Manifold Absolute Pressure Sensor (MAP) and the Air Intake Temperature Sensor and tuck the cables somewhere out of your way. You can take this time to clean the connector with an appropriate electrical connector contact cleaner. This will make sure they function well for the years to come. You'll get a chance to inspect these two sensors later when we remove them from the manifold. For a future project if you want to know your manifold pressure or intake temperature, you can run a gauge off these sensors...

Step 2:
Using your 8mm socket loosen the bolt holding the turbocharger hose that connects the turbo to the intake manifold, only loosen the one shown in the picture, not the other one as it is not necessary. If you feel like it go ahead and loosen the two 8mm bolts and clean the hose, mine was very dirty and full of dried silicon someone had used to seal it to the intake manifold. If you notice your hose is cracked, it may be the time to change it. You might be loosing air pressure from your turbo! SS Diesel Supply sells one for 24.99$US. Do not remove the bolts completely as the small spring may fall and then trying to find it might not be really easy. Next using your 13mm socket remove the big bolt that holds the turbocharger to the intake manifold. Lastly using your 10mm socket remove the 6 bolts that hold the intake manifold in place. Your upper intake manifold should now be free, go ahead and remove it! 

Step 3 (Optional):
With your upper intake manifold removed you can go ahead and give your turbocharger hose, lower intake manifold and upper intake manifold a good clean. If you want to clean your upper intake manifold, be sure to remove the Manifold Absolute Pressure Sensor (MAP) and the Air Intake Temperature Sensor beforehand. The MAP is simply held down by two 8mm bolts. The Air Intake Temperature Sensor is screwed into the manifold, use a 19mm deep socket to remove it. I recommend you to remove the two sensors and giving the manifold a good clean in the sink with a good soap and scrub. The interior of mine had oily deposits and sticky sludge from the hundreds of thousands of kilometres of driving. I included pictures of what my parts looked like before cleaning.

Step 4:
Now that everything has been removed and thoroughly cleaned, we are ready for the PMD upgrade. Before installing the new PMD we will have to disconnect the ground wire and connector of the old PMD. Now that the upper intake manifold is removed, it will be much easier to access the old PMD. Go ahead and use your Torx T25 bit to unscrew the ground screw. Once removed put the screw back in place. You can then remove the connector to your old PMD. You need to unclick the latch then it should come right off. Now pull the cable gently and try to get the longest out of under the manifold to hopefully have enough to connect to the new PMD. If your cable is stuck and you can't get enough loose it might be tangled in the injector lines. You will have to get an extension cable, they are available from SS Diesel Supply at 29.99$US. In my case mine was just enough long to get to the new PMD, but to avoid future rubbing issues from engine vibration, I'll get an extension cable.

Step 5:
With the PMD cable and ground screw disconnected, we can begin to reinstall what we removed earlier. You will need a new intake manifold gasket. You can get it from pretty much any parts store for under 10$US. The old gasket is almost certainly dried up and reusing it would be stupid because you'd almost certainly loose boost pressure. Be sure to remove the old gasket and clean the mating surfaces so the new gasket is properly seated. When reinstalling the intake manifold if you kept your old turbocharger hose, you can put gasket maker paste of silicon to make sure it has a good seal. When putting back the 6 intake manifold screws, don't put in the two on the drivers side because this is where we will put the FSD Heat-Sync.

Step 6:
This is the best and final step of this project. Go ahead and secure the FSD Heat-Sync to the Intake Manifold using the two remaining screws. Tighten the 6 Intake manifold screws progressively in a clockwise pattern. This will get the gasket seated evenly and give you a better seal. Now, simply connect the PMD cable in the new PMD and secure the ground screw to the side of the Heat-Sync using your phillips screwdriver.

Once you have completed all these steps, verify that all screws and bolts are tight and that you haven't forgotten any tools in you engine bay, and go ahead and start up your engine. For my part I noticed that the engine was much smoother and stuttered less on startup. After 1000km of driving the FSD Heat-Sync still holds and I never had anymore hard starting or random engine shut offs anymore! Keep reading because in the next post I'm putting a modified Police Lightbar on the Diesel Suburban to give some serious off road lighting!

Thursday, December 9, 2010

Supersizing the wheels!

For the first post on this spanking new blog, I'll be talking about the first upgrade I brought to the truck. Since the tires were totally used up when I bought the truck I needed to get some new ones. Moreover the OEM silver painted rims were all rusted so I needed some new wheels as well. I went looking over the internet for the biggest possible wheels that could fit onto the GMC Suburban without having to do a body lift. I know I'll do a body lift eventually, but for now I neither had the time or money to do it.


From my calculations and observations from looking around a 285 75 R16 tire would be the biggest tire to fit the Suburban. I looked around for good tires in that size that would be both affordable, be rated for extreme snow conditions (mountain snowflake symbol), and have good all terrain performance. I already had a weak spot for the Goodyear Wrangler series because of its look and popularity. I was deceived to see that most tires in this series aren't for extreme off road. I had either the choice of going with the Wrangler Duratrac or Wrangler MT/R. The problem with the MT/R is that they aren't rated for snow extreme conditions, and where I live as of 2014 it is required by law. I then had pretty much no choice than to go for the Duratrac. They make the E load rating (10 ply) version for this tire so it would be both able to take the heavy Diesel Suburban anywhere and be able to resist pointy rocks and scrap metal. I bought 5 tires for 259.99$CAN each at a local store but you can also find online for about the same price. Buying them local had the advantage for me to get a special warrantee in which if a tire gets punctured I can get it repaired at my local store for free.


The stock tires being 245 75 R16, the new tires would be much much larger (40mm to be precise). This would make fitting the new tires on the OEM rims doable, but neither recommended nor safe. I went ahead and looked for 16 x 8 rims. Why stay in the 16 inch diameter you ask? Well I love the look of beefy tires and they do provide much better traction in deep snow or mud and can be deflated to a greater extent than low profile tires to augment grip. I didn't want to go with some weak aluminium alloy rims so I absolutely wanted to go with steel. So the search was on for some heavy duty 16 x 8 steel rims. That have an 8 lug pattern as used by the Diesel Suburban version. I found that the Pro Comp USA Rock Crawler Series 52 Black Powder rims were exactly what I needed. I purchased them from for 115.99$CAN each.

Fitting them on the Suburban:

Like I said above, the 285 75 R16 are the biggest rims that will fit on the Diesel Suburban. However, there is some minor trimming to be done to fit those monster wheels. The front bumper and plastic garnish has to be cut in a 45 deg pattern. The other side of the rear well needs its mud flap and other plastic and metal brackets to be trimmed down. This allows the wheel to turn fully and the suspension to compress without hitting anything. The rear wheels don't need to be modified at all. Hope you have enjoyed this first post and look forward to much more...