Engine shutting of

[Ed T]

Hi all, here's my scenario. Where would you start troubleshooting this?

1999, K3500.
The engine was rebuilt within the last 5 years. It has less than 20k since rebuild.

I drove 1/2 mile and parked for 3 hours. All is well.
I then drove home when the engine died. I was able to coast to the curb.
The engine never got up to temp so I'm thinking it’s not the PMD. Although the PMD is at least 15 years old.
I tried starting the engine but it did not start.
I tried starting again with success.
I put it in gear and started moving the truck. The engine died again.
I turned the key to start it again but it wouldn't start.
I turned the key a 2nd time with success.
I put it in gear, moving the truck 10 feet and the engine died again.

I'm stumped. Where to start troubleshooting.

The engine was rebuilt within the last 5 years. It has less than 20k since rebuild.

Lift pump? Replaced during engine rebuild. I can hear it click when I turn the key to warm the glo plugs.

I am replacing it today just to be sure.

PMD? I ordered a new PMD from Leroy Diesel and will replace it this week.

Some folks have suggested the ignition switch?
I will check the fuses today too.

Thank you everyone.

[DmaxMaverick]

Welcome aboard!

It sounds like you're headed in the right direction. The PMD and ignition switch are the usual suspects. Low battery voltage and grounds are, as well. When it did restart, did it seem "normal" (until it died again)? If so, not likely the lift pump, its relay, or air in the system. Even when the lift pump fails, they rarely cause stalls if you have successful starts. A used up injection pump can depend on the lift pump for starting and running, but there's almost always other issues with it. This would be an instance of temperature being a factor, but again, once it starts, it won't cause a stall, and it's very unlikely to have random issues.

Is the SES lamp on? If so, can you pull codes? Failing/failed sensors can cause starting and running issues, but the computer won't hesitate to complain about them.

[Robyn]

The PMD is always a prime suspect in sudden stalling.

The PMD FAILS in two distinct variations.

(1) As you are seeing.....start..run and then shut off.
Restart or no restart....cool off a bit and then repeat the same scenario.

(2) Engine goes to full fuel and will not idle down...In neutral the engine will reach RED LINE and the ECM will shut off the fuel solenoid on top of the IP.

This type of failure can be quite exciting and greatly increase the need for a change of shorts after the event is over.

If (2) happens on the road and the vehicle takes off....simply leave the tranny in gear and shut off the ignition...coast off the road safely.

In the parking lot or ??? with the vehicle in park the engine will scream and shut off well before you can do much of anything except gasp and see your heart rate climb off into the ozones.

The ECM will shut it off long before pieces start to fly.....but the area will take a few minutes for the black smoke to clear.....

Replace the PMD first......If the PMD is not relocated to a cool place...do so on a good heat sink....

Extension cables are available.

Always keep the ground wire attached to the IP as it was from the factory.

Good luck
Keep us in the loop

[Ed T]

Thank you both the excellent replies. To shed more light on your comments.

This is my 3rd PMD. Both replaced many moons ago, so I know what happens when it gets hot. In this case the PMD is NOT getting hot. I only drove the truck half a mile. It sat in 50 degree temps and then I drove another half mile back home. My thought was, maybe it's just PMD going bad and it's electronic life is done? I have a new one coming along with the relocation kit.

When I did get it restarted, it sounded perfectly normal. Then just shut itself off.

The SES lamp did NOT come on, so I can't pull a code.

I will keep you posted on my progress.

Thanks again.

[DmaxMaverick]

Recommended PMD test procedure:

1) Locate yourself and the PMD near a large body of water (lake, pond, ocean, Mississippi River, etc.).

2) Throw said PMD as far as you can into said body of water.

3) If it floats, it's good.

NOT recommended for new PMD's.

[JohnC]

NOT recommended for new PMD's.
However, it does have very good predictive value...

[Robyn]

The Failure of the PMD is aggravated by heat.....but once the internal electronic components degrade to "A certain point" they fail, and the heat thing is a moot point.

As mentioned...THE FLOAT TEST.....pretty much it.

A shutoff condition with a restart and NO CODES...OR OTHER ODD BEHAVIOR is nearly always the MO of a failing PMD.

Having a spare in the glove box and a few tools is always a good idea on one of the 6.5 electronics....

Sadly...the PMD internal components are all encased in a "Potting compound" " (Sort of like JB WELD) that conducts heat away from the parts.....or at least that is the idea.

Also the potting compound makes it nearly impossible to really see whats in the little beast and to be able to back engineer it. Some obviously have as the after market has seen replacements.....

[Ed T]

Hello again, Some ideas have also been the ignition switch.

I haven't had the chance to do any work on the truck yet, but my curious mind is trying to grasp how the ignition, and key once rotated to a spot where all the electronics are connected and working, cause the engine to simply shut off? Bumps in the road creating a ground to shut the motor off?

[JohnC]

There are several sets of contacts in the switch. The transmission and instruments are independent of the PCM, so a momentary interruption of the engine circuit, which would likely cause a stall, would not show up in the instrument panel, for example.

[a5150nut]

Its not the key tumbler but it is a small box on the lower steering column. The connector itself can become crisp and be a short.

[DmaxMaverick]

The ignition switch is one of the most common failures among GM vehicles, and likely of most brands. Unlike your lawn tractor, motor vehicle ignition switches don't have only one on/off circuit, as John said. While they most often fail the acc. circuit first, any of the circuits can fail at any time, possibly effecting only one system that you may notice. Many late models don't even have an ignition switch, such as our Volt. It has only a momentary button switch that tells the computer that a start is desired. The computer and an array of relays do the rest. Scary as that may sound, they've proved no less reliable than keyed switches. The relays are much more accessible and easier to replace than most traditional switches.

[More Power]

The PMD (or FSD as it is also sometimes known) was the single-most problematic component on the entire 6.5TD powered vehicle. For a long-long time I recommended every owner install a remote mount kit for the PMD and have a spare "known-good" PMD as a spare... Think of it as no less important than a spare tire. A remote mount kit allows you to swap the PMD on the side of the road with nothing more than one Torx bit tool and a flashlight. A spare known-good PMD also provides you with a valuable troubleshooting aid in times just like what your truck is experiencing now.

Sure, an ignition switch can be a cause of stalling, but I've only ever heard from a tiny number of owners who identified that as a problem... in 25 years and more than 100K emails/phone calls. A simple volt check of the associated IGN/ECM fuses when the truck stalls would be one way to verify that possibility. A wiring problem (pinched or damaged during some other recent service) or a corrosion problem that affects an electrical connector (usually associated with road de-icer) has also produced a few identified causes of intermittent engine running problems... a few.

I recommend only the latest gray colored Stanadyne module. If you buy a new module, be sure to obtain a new calibration resistor to go along with it. I recommend a #5 resistor. If your DS4 injection pump had/has a black module, you'll also need a new pigtail harness for the pump... the connector design is just slightly different. You'll need to remove the intake manifold to replace that pigtail. The Troubleshooting & Repair Guide shows how to properly and safely R&R the intake.

Jim