The PMD Isolator System & How It Works

The GM 6.5 PMD Isolator system for 1994-2000 GM 6.5 by Heath Diesel.

It is well understood that the PMD (pump mounted fuel solenoid driver) does not survive well as located in its factory location on the fuel injection pump.

In doing its job, the PMD creates considerable heat and requires a heat sink in order to dissipate that heat. The harder the engine is worked, the greater the level of heat generated by the PMD.

In theory, the DS-4 fuel injection pump was to function as a heat sink and mounting the PMD onto it was to provide a sufficient heat sink mass to absorb heat being generated by it. However, in practice, mounting the PMD onto the DS-4 fuel injection pump is not a practical solution as the DS-4 operates at a temperature ranging upwards of 180*F. As a result, the PMD cannot effectively dump enough of its own generation of heat and is forced to operate at very high temperatures.

Testing has shown that the PMD works best and lasts longest when its temperature is controlled to some point below 150*F and this is not possible when it is mounted onto the DS-4 injection pump. Temperatures anywhere inside the engine compartment are too high for the PMD, inhibiting its ability to function properly and shortening its service life.

The only proper solution is to mount the PMD complete outside the engine compartment, so that it can operate at safe temperature levels. The Heath Diesel PMD Isolator system is designed to remotely mount the PMD completely outside the engine compartment for premium performance and long service life.

The PMD Isolator system includes a new PMD module that features a ‘resurfaced’ mounting surface. It is joined to our Isolator plate with 4-mounting screws as well as an epoxy which provides a very high co-efficient of heat transfer. This method assures full and complete extraction of heat from the PMD. The result is improved fuel injection function and very long service life.

The Isolator plates are constructed of 6061 aluminum alloy. The plate is .300” thick and laser cut to exacting dimensions. The Isolator plate provides the heat-absorbing mass necessary to allow an effective transfer of heat from the PMD into the passing air. This allows the PMD to operate at approximately 7* over the ambient temperature, so that it stays very cool.

The PMD Isolator system is tethered to the engine by a special, 74”-long harness, allowing the unit to be mounted far away from the hot engine compartment.

The 4-wd version mounts the PMD Isolator plate onto the forward surface of the front skid plate, just below the radiator, behind the license plate assembly. When assembled to the skid plate, the PMD module is housed behind the Isolator plate and between it and the skid plate. It is impervious to weather and not subject to road hazard.

The 2-wd version uses an Isolator plate that is configured differently than that of the 4-wd. This plate mounts to the upper surface of the lower flange of the front bumper, utilizing two of the existing holes in that bumper flange. It extends straight back from its mounting.

While longevity is the goal in the PMD Isolator design, they do provide a slight gain in power (5-6hp) over that provided by any of the higher temperature, under hood locations. The PMD Isolator system is warranted for 7-years with a free replacement part warranty. Many have been in continual service for more than 11-years. Solves the problems associated with the PMD---once and for all.

Questions about this or any Heath Diesel product? Feel free to contact us anytime 1-877 894 6266 or sales@heathdiesel.com

- Bill Heath

Related Links:
PMD Isolator Systems for Chevy/GMC 6.5
2-wd PMD Isolator System
4-wd PMD Isolator System
GM 6.5 Diesel Parts