Intermittent DTC 35 & 36

[bsevans]

I started getting an intermittent SES light about a month ago that was due to DTC 35 & 36 codes being set. I read on this forum that I should first start with a lubricity additive and then a PMD before going the route of a replacement injector pump. I started with a lubricity additive from Stanadyne and the light did not come on for days. When it did come back on it would light almost every time I used the accelerator and go out when I lifted off. I decided that the next step was to replace the PMD. I purchased a kit on eBay that included the new Stanadyne grey PMD, a grey PMD #9 resistor and an 8" extension cable that converted the old connector to the new PMD keying. It has been a month and not one SES code has been set according to my GMTDScan Tech software. I've added photos of how I've mounted the new PMD. I put washers between the three mounting points to minimize the conductive path to the heatsink from the intake manifold.

[More Power]

Thanks for posting the results of your tests. Always good to hear of a good result.

Jim

[DmaxMaverick]

That's the second-worst place to mount the PMD/FSD. The only place worse than that is bolted to the exhaust manifold. You've moved it from "hot", to "hotter". It may be in a more convenient location, but you aren't helping to keep it cool. Either leave it installed on the pump, or get it out of the engine compartment completely. Don't believe me? Start your truck early on a frosty morning and idle it until the ice on the hood begins to melt. Notice where it melts first and how quick it does. Compound that many times for an engine under load with the thermostat open.

[bsevans]

That's the second-worst place to mount the PMD/FSD. The only place worse than that is bolted to the exhaust manifold. You've moved it from "hot", to "hotter". It may be in a more convenient location, but you aren't helping to keep it cool. Either leave it installed on the pump, or get it out of the engine compartment completely. Don't believe me? Start your truck early on a frosty morning and idle it until the ice on the hood begins to melt. Notice where it melts first and how quick it does. Compound that many times for an engine under load with the thermostat open.

My Fluke Infrared Thermometer certainly disagrees with your statement. The Omega temperature indicating strips mounted to the pump and the old heatsink I had mounted in the same location (see photo) also disagree with your statement. As far as remote mounting of the PMD, I would rather have it mounted with an 8” extension rather than a 6’ extension because a 6’ extension can have issues with signal strength and timing. With the engine running and/or the vehicle moving the flow across the heatsink fins has excellent convection properties resulting in far better cooling of a PMD than it ever had mounted to the pump. The temperature of the injection pump with a working lift pump is problematic at best as far as conductive heat transfer due to the temperature of the injection pump. It is abysmal with a non working lift pump which most times is due to a failure of the OPS as the switch for power on the ’95 6.5TD. I made a custom Weatherpak harness that uses the fuel solenoid circuit as the relay trigger for powering the lift pump and have had a working lift pump ever since. We clearly disagree and that’s OK.

[DaveBr]

You are better off leaving the PMD on the pump than putting it where you have it. Take the advise and get it out of the engine compartment or buy another one so you won't be stranded when it fries.

[DmaxMaverick]

Fix your lift pump and try again. Then, run your temp tests again, and factor in the heat transfer efficiency of free air vs. fluid. The pump is hotter (not by much), but will remove significantly more heat than the hot, free air under the hood.

[bsevans]

Fix your lift pump and try again. Then, run your temp tests again, and factor in the heat transfer efficiency of free air vs. fluid. The pump is hotter (not by much), but will remove significantly more heat than the hot, free air under the hood.

If you had correctly read my post you would understand that I already fixed my lift pump or at least the source that supplies power to it. I stand by my measurements both IR and Indicator strips.