1999 Suburban 6.5l won't start
 

Truck has 122K. From Florida, truck stuck in Columbus Georgia. Dealer doesn't have experience with the older diesels (WHAT). Back to square 1. Told me to come pick it up. History with truck. About PMD, replaced and relocated on heat sink about two years ago due to truck not starting. Then LP goes bad, replace (ac delco), change fuel filter and truck runs fine. Ran great for several thousand miles then had issue with irractic idle and runaway throttle. Call numerious repair shops and they point to IP ($2300). So I replaced with another PMD based on info from forum. Ran fine for 700 miles. Truck then starts to intermittenly stop with sometimes hard starts. Replaced PMD again due to symptoms just before trip. Ran great all the way to Georgia and we know what happens. Shut down truck in parking lot and won't restart. Same symptoms as those other bad PMD's. Run to parts store replace with a Dorman PMD. To my surprise, doesn't fix the issue. Truck won't start. What can I look at to get my truck running again. Could it have been a faulty PMD I bought when I was there? What can burn out a PMD. Maybe that is where I need to look. Please help with any info.:scare2:

If your heatsink/PMD combo is mounted under the hood on the intake it is the worst location possible.
It should be outside the underhood area,under/behind the frt bumper or behind the grill on a rad support.

Also if the IP harness ground was moved to the heatsink to let the harness reach an intake mounted combo it could be a the main problem.
The IP harness ground can ONLY be mounted on the IP or the drivers side battery ground-no where else.

Some trucks won't start if there is no resistor in the PMD.

Are you using a heat transfer pad or heat transfer paste between the PMD and the heatsink-it is required.

Ignition switches fail and cause no power to the ECM.

Fuel shutoff solenoids on the IP fail and make for hard/no starting.

Please hit enter once in a while so your posts are easier to read.

Thanks for the reply. Sorry for the lack of enters.
PMD is on a heat sink with pad and #9 resistor.
It is mounted in the front bumper with plenty of airflow.
Grounds are good, as for ignition or fuel shut off solenoid I don't know.
Can the solenoid be replaced by it self without replacing IP?
Where is it located exactly?
Truck is being towed back home. Called another mechanic who has already mentioned the IP. How long do these electronic pumps last in the 6.5's?

The FSO can be replaced without replacing the IP,it is at the frt of the IP and looks like a stack of 50 cent pieces with a couple of wires connected,it just screws out of the IP but can be very hard to get out if the O ring is stuck and often wrecks the FSO when you do try to remove it.

If you hold your hand on it and it clicks firmly when the key is turned to run,it is likely working.

Have you checked the fuel/sol fuse?
It powers the PMD,the fuel solenoid and the FSO.

The PMD being mounted on the fender is not ideal,having airflow while good when driving does not help when the the vehicle is shutdown and underhood temps skyrocket from heatsoak.
A sudden temp spike in any direction it what aggravates the internal connections of the PMD,over time the repeated temp swings work the connections and they fail.

Mounting the PMD combo outside the underhood area is best so that it stays at or near ambient temps at all times.
With a quality extension harness and the proper medium between the PMD and heatsink, moisture is of no concern.

Heath Diesel did a test with a PMD/heatsink/resistor combo immersed in a bucket of water and no problems were encountered.

Also while it is good to have all grounds in good shape,the IP harness ground must be fastened to the IP or the drivers side battery ONLY!

The length an IP can last is not something that can be measured,if the truck has run for an extended time with a non working LP-it can damage an IP very quickly.
Or if no lubricity additive is added to the fuel then the IP also wears more quickly.
Likewise some rebuiders re-use old head and rotors while others rebuild with new parts-both affect how long it lasts.

Thanks for the fast response. I will look at these issues when I get my truck back this week. You gave me some great info and areas to investigate. I've seen some of your other posts and responses. Impressive