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View Full Version : HELP - 6.5TD Intermittent stumble/stall when cold, now won’t start



TurboDiverArt
04-28-2013, 05:27
Hi all,

After having a relatively trouble free 250,000 miles my 1999 Surburban 6.5TD began to develop a stumble when first started until it warmed up. Would not do it all the time, just sometimes. Sounds like it just doesn’t get fuel for a fraction of a second then it’s fine. Occasionally it would stall but always started right back up. Never happened once it’s warmed up and ran like a champ. Went to start it this morning to tow to the track but it won’t start at all. Just cranks, not even a hint of wanting to start at all. I changed out injectors and glows last year and truck had been running great. I would have thought the PMD but doesn’t that usually fail when hot? I have mine mounted on a remote cooler. I have a spare but the pin outs on the replacement seem to be different than my factory one (have to contact the vendor I bought it from). My brand new spare has all 7 pins in it, my factory wire harness has one pin and 6 holes and mates perfectly with my remote PMD wiring harness. I guess I could try to connect the factory wire harness to the factory PMD that’s still on the pump. It’s difficult to get to my remote PMD harness but I may try that next.

Anyway, I’m wondering if maybe it’s the solenoid on top of the injector pump? I assume this is the mechanical solenoid that the PMD controls? Cylindrical and pointing straight up in the air with what appears to be a nut on the top. I think the rectangular thing sitting on its side next to it is the shut off solenoid? Could that be bad?

After trying and cranking for a while I do not smell any diesel in the exhaust pipe so I’m pretty sure its not getting fuel.

Robyn
04-28-2013, 08:12
The cylindrical gizmo is the fuel shut off, and is controled by the ign key to shut the engine off, and will be activated by the ECM in the event of an overspeed condition.

The PMD has nothing to do with this solenoid.

The PMD controls the metering solenoid inside the IP
The square block (black) just aft of the round tall solenoid is the optical sensor housing connector.

Three things come to mind.
The shutoff solenoid could be failing.
The PMD is going south.
There is air getting in causing a fuel drain back.

Have someone help and turn the key on and off while you listen and feel the solenoid, it shoud click.

Replacing is a simple unplug it, unscrew it and screw in a new one.

Swapping in a fresh PMD is always a standard diagnostic tool.

Never trust a PMD, NEVER

Fuel drainback can be a tougher bug to find.
The addition of a check valve on the inlet side of the lift pump can help.

One other thing to check is to be sure the lift pump is working on startup, and then continues to run with the proper delivery volume and pressure.

In fact, be sure the lift pump is working right before spending any $$$ for anything other than an obviously failed Fuel shutoff Sol.

Keep us posted

Missy