good result

[alberta]

Replaced the fuel shutoff solenoid as advised by Robyn and the stalling problem appears to be gone(after months/yrs.)I also experience a more brisk start.Robyn what causes this solenoid to fail? The FSD is not remotely mounted.I'm amazed how hot the engine compartment can get.There isn't an area that you can keep your hand on.It would seem that the air intake area in the bumper would be best.Vehicle is '94 3500 6.5L TD crew cab 135000.Guage temp 190.

[Robyn]

There are several things that can cause the solenoid to fail.
An electrical issue in the coil such as a short or a bad connection.
A binding in the armature that either keeps the plunger from moving or ??

This little solenoid has to move everytime the key is turned on and the engine started.

The plunger is pulled upward to remove the little stopper from the fuel passage to allow fuel to flow to the pump.

Its like any other electrical part and therfore can fail in due time.

If fuel leaks into the coil and causes issues with the winding, you can have problems.

Just no really good way to pinpoint the "WHY"

The early ones with the crimped in hex top had issues more so than the later design.

It has not been a chronic issue though on the DS4 pumps.

As far as the best location for the PMD goes ?????????//

I like mounting them on a good heat sink on the top side of the skid plate that is just below the radiator.

Its relatively cool down there and protected from most debris.

Unless your doing deep fording or real sloppy Mud running, this spot is a good one.

The nostril in the bumper is OK too.

The biggy is to get that PMD away from the 250 +++ F heat souce and allow the thing some reasonably cool airflow.

Using a DTECH PMD is a good deal as these units were designed to handle a lot more heat than the OEM ones can take..

Glad you had success with things.

Missy

[alberta]

Robyn Thanks again for your guidance.Even though you don't implicate the PMD as a likely cause in the fuel shutoff solenoid failure,I'm inclined to a remote mount.

[Robyn]

The PMD is not on the same circuit as the Shutoff solenoid.

The power feed to the PMD comes in on a different leg of the 12V.

The solenoid is either on or off.

The PMD has power fed to it and the ECM then controls the PMD.
The PMD basically uprates the power signals coming from ECM to a level that can operate the internal fuel metering solenoid (Not the shut off)

The PMD fails due to the heat load thats placed on it and its inability to shed that heat.

The PMD has two high power transistors and they are potted in the case of the PMD. Under operating conditions, these transistors generate a lot of heat that is supposed to be shed through the case of the IP and then via the cool fuel running inside the IP back to the tank.

All sounds good but in application it failed misserably due mostly to a poor design choices.

The DTECH PMD was designed using components that have a greater heat resistance and therfore far better durability.

I have seen many PMD's go away, but only two Shut off solenoids and one of those was fuel leaking through the case and the other was a failure to actuate.


Best

Missy