Hi guys,

Since yesterday out of the blue i am having problems with my H1, the car is located in Lima, Peru. It has been working fine since i bought it, the weather here is around 70 degrees all year round, and the engine operating temperature never reached the middle of the dial. I have been driving only in the city and very slow due to traffic and driving habits.

I start the engine and it runs perfectly, idling very smooth, everything seems fine, then it suddenly quits. Then i start it again right away and same thing, it idles perfectly for about 20 seconds and then quits.

I have heard about the FSD getting damaged due to heat, but my engine really never overheated. I have no clue how the previous driver treated the car, but i have it for almost 3 months and drove it for 2.5 thousand miles with no problems at all, and then suddenly this.

Can you guys advice me in how to pinpoint the issue.

Thanks a lot

Christian

 

This probably is the answer but, I started up my H1 the other day, just bought it, and after starting it up the ignition bounced backwards and turned it off. I started it up again and in a more gentle fashion brought the key back to the on position and it stayed. I was surprised that the spring action from the turning engine over position was able to return back past the on position to off. Do you think there might be something in the ignition that keeping the key in the one position.

This is probably a long shot but I thought I would mention it.

Is the check engine light working?

Take care and have a good day

Forsche

 

Sounds like the PMD on the injection pump is starting to fail. Your motor doesn't have to overheat for the PMD to fail. heat is one thing that helps cause their failure but general deterioration over time along with the heat will help cause the PMD to fail. You can pour cool water on it when it overheats and it will generally start up and run for awhile after that. That will at least get you home.

 

Ok this is the wierdest thing ever...... mine ( same year and style ) just started doing exactly the same thing last week!!!

Can you tell me what a PMD is? Can i order it from AM? and how hard is it to replace? I think I definatly need a new one.

Any help would be great,

Brent

 

PMD = pump mounted driver. The injection pump is on top of the motor on the passenger side of the engine. The injection pump sits next to the valve cover and the PMD is on the side of the IP facing the center of the engine. They can be ordered through any authorized AM General reseller such as Tustin Hummer, in Tustin, California. I have not replaced one but many people change them out themselves.

 

PMD = pump mounted driver. The injection pump is on top of the motor on the passenger side of the engine. The injection pump sits next to the valve cover and the PMD is on the side of the IP facing the center of the engine. They can be ordered through any authorized AM General reseller such as Tustin Hummer, in Tustin, California. I have not replaced one but many people change them out themselves.

Note: The FSD/ PMD (same thing) is a small black box on the side of your injection pump. It is a signal amplifier that powers the fuel solenoid on your injection pump. It has 2 transistors mounted on it's backside that generate heat that has to be dissipated. In it's stock location it can over-heat and fail.


The story usually begins like this. You’re driving along and the engine just quits. You lose your power steering and the truck is very hard to steer. You pull over to the side of the road and you are able to restart. After a few days the stalls become more frequent and the truck will be hard to start. You realize that you can’t trust the truck and something has to be done. This is the classic symptom of a failing Fuel Solenoid Driver (FSD) also known as a Pump Mounted Driver (PMD). This is an electronic switch that controls the fuel flow on a Stanadyne DS-4 electronic injection pump. Electronic injection pumps are used on all Hummers with the GM 6.5 turbo diesel between 1996 and 2004. A failed FSD will not display an engine light. Pictured above the FSD is a small black box about the size of a deck of cards bolted to the side of your injection pump. It is an amplifier that receives signals from the engine computer to pulse the fuel solenoid which tells the injection pump to send fuel to the engine. It has 2 power transistors mounted on the back that generate heat that has to be dissipated. The injector pump is mounted deep in the center valley of the engine in a very hot environment. The FSD is exposed to heat that can cause it to fail over time.

The Stanadyne DS-4 pump has been used on GM trucks since 1994. Owners of older Chevy and GMC trucks and G-Vans have experienced these problems years before Hummer owners have. GM had so much trouble with early generation electronic injector pumps that they had to warranty the units for 100,000 miles. When AM General purchased these motors from GM they did not get a 100,000 mile warranty. In 1999 AM General bought the plant and took over production of the 6.5 engines later that year.

Heat generated by the FSD is supposed to be carried off by the diesel fuel flowing through the pump. While this is true, the damage is being caused right after the engine is shut down. After you stop the engine the fuel of course stops flowing and the water pump stops circulating coolant which in turn causes the engine temperature to actually spike for a short time. This is called heat soak. This rise in temperature heats the FSD which is bolted to the injection pump sitting on top of the engine. The continual heating and cooling cycles cause the FSD to fail over time.

There have been 3 variants of FSD's. FSD's with a 30214 on the case are the worst. This is the first generation and the most prone to fail. FSD's with a 34264 are second generation, and are preferred by some Stanadyne repairmen because they will either work, or won't work, like "a light bulb". The third generation number 34583 was designed to allow you to "limp home" by operating for a short while and then fail.

Because the injection pump is deep in the valley of the engine the FSD mounting screws are almost impossible to get at unless you remove the manifold (which is a major job. I've spoken to a couple of mechanics that were able to get the FSD out by using a very short torx bit wrench but I can't see how it was done.

If your FSD needs replacing it seems unwise to put it back where it was, down in the heat. Why not save all the trouble and labor and simply mount the FSD on a heatsink somewhere away from the engine where it can stay cool.

There are a number of aftermarket products that have specially designed heat sinks and extension cables that let you remote mount your FSD in a cooler spot. The kit used in this article is from Flash Off-Road. This solves the problem once and for all.

FSD’s have a calibration resistor pack that describes the pump to the electronic control system. Because there is variability in the manufacturing of injector pumps the resistor is used to calibrate the engine computer to the pump. The resistor pack is a small circuit board with a resistor that is inserted deep into the FSD’s socket. New FSD’s don’t come with resistors.

The #5 calibration resistor is considered the "average", and almost any pump will work with a #5 resistor. The resistor is only used when the control computer forgets what the value is, which occurs after the batteries are disconnected or a hard reset is performed with a tech tool. If you don't use a resistor you will get a p1218 error code when the computer tries to read the value. Your truck will still run.

Whenever I run into a failed FSD I always replace it with a remote mounted unit on a heatsink and just abandon the defective FSD on the injection pump.

If you go to the site there are pictures to help you understand the text even better.

This write up is from www.flashoffroad.com. Lots of great how to articles there. It is a great resource for Hummer owners. If you get some benefit from it you might consider making a small donation to Chuck to help offset the expense of keeping the site open.

 

Will a scan through the OBDII port will give a code error for the FSD/ PMD if is defective?. Thanks a lot.

It should. I don't have my scan codes handy to tell which code it is.

 

Great info, I'll store this in the memory bank for future sake.

Thanks

 

Well I got it fixed, I read the information posted (very good info thank you) and it soon became obviouse this was way beyond what I was interested in doing myself.

I took it to the Diesel shop it was some sullinoid in the pump, they had to replace everything, I had them do the serpintine belt and fluid flush as well. $3100.00 later I am back on the road and think I might sell my truck. what a rip off.

Brent

 

Sounds pretty high. An IP can be totally rebuilt with a new PMD for about $850.00. Add in 4 hours labor to replace it and 12-1300.00 is in the ballpark. Retail for a new IP is about $2100.00 if I remember correctly. It helps quite a bit to communicate with the Hummer community when you have these issues. In many cases you can get great information on where to take the truck to get fairly treated.