Ok, I've been driving the truck as my daily for the last 2 years and it has carted me all over the country. So it's been reliable.

I have replaced and relocated behind the grille a new PMD. Have not had a problem with it since I did it.

OPS was replaced before the PMD, though it was not bad.

Fuel filter was replaced a few weeks ago.

Inline/ frame mounted pump is working, I can hear it. There has been a small leak around the pump for as long as I've owned the truck. It doesn't leak enough to drip on the ground, but enough to leave a mark on the rail.the truck still gets 20+ mpg, and its all high pressure steel lines that seem like a pain to replace so I have just never done it.

Here is what happened.
I bought a car but have been doing some work on it, so I have been commuting in my truck every day the past 2 weeks with no issue. I got up to go to work today, the truck barley fired (right away) and died. Then it cranked, but no fire.

I took another car I have to work, then when I got home, tried it again, nothing.

So I crack the T-valve to test the injection pump and other fuel pumps, or at least see if it was getting fuel to the motor.

Stuck a water bottle under the drain hose, hit the key, truck fired right up, diesel was draining into the bottle off the T-valve.

Ok, so I closed the T-valve, let it idle a little bit, shut it off, start it and it fires back up. Go get rid of the wasted diesel, come back, try to start the truck again after it sat for a few minutes, and nothing. Just cranks away

So, does anyone have any idea why the truck suddenly only wants to start with the T-valve open? Could the fuel line leak have gotten worse and caused a bleed back problem? I am at a loss as to what this could be.

Thanks for any and all help
J

 

Sounds more like a failing PMD or an extension harness problem.

Did you use heat transfer paste/pad between the PMD and the heatsink?
PMD resistor installed?
Any corrosion on the resistor or extension harness?

When you get a no start,crack a fuel injection line loose from an injector and check for fuel at the injectors while cranking.

 

I haven't checked the PMD again yet. I plan on plugging I one of my old PMDs to see if it will start on that. My current PMD is a XDP aftermarket one I bough brand new a little over a year ago. It is bolted to a heat sync with the paste between it. I believe it is the #9 resistor (whichever one was the highest flow).

Now the truck won't start at all, even with the t-valve open. However fuel still flows out if the t-valve is open. Also, it is not smoking when I am tring to start it (which I remember it. Doing when my PMD went bad the last time).

I will try to diagnose if its a PMD issue tomorrow or Friday.
However, all the PMD issues I had in the past were hot start problems, this is a cold start problem. And it was sudden, truck was driving fine daily, woke up to go to work after it had been parked all night and it wouldn't start.

I'll also crack a line and check the injector as well. Thanks for the suggestion

 

PMD's can fail hot or cold so don't go by that.

 

Ok, so I tested the PMD with an old one that I had sitting around, still didnt work. Inspected all wiring for corrosion and wear, it all looked good. Still wouldn't start. Cracked an injector to see if there was fuel to the motor, truck started. Then I drove it probably 15 miles round trip with no problem. Got home, shut it off, let it sit for 45 mins, tried it again, fired right back up. So the PMD is fine, there is fuel at the injectors, and the truck runs fine once started.

 

I would not say the PMD is fine yet-perhaps you fixed a bad connection during your tests but it still smells like a PMD problem.

 

Problem is getting more confusing. Truck drove fine the other day after sitting for about 10 days. Sat 1 more day after driving it, started hard, died after roughly idling for 15 seconds like it has in the past when it first starts after sitting but smoothed out in 30 secs. Now it won't start, no fuel at the injectors any more. Double check PMD again and its not the culprit. Still have fuel at the t-valve

 

Have you eliminated the ignition switch as the culprit?
It is a muti contact switch that can burn out ECM power contacts but the radio and blower motor works fine,can also be intermittant problem.

 

Hmm, no I have not? The motor still turns over like it should, would this be affected? How do I test it? Also, ive read that the fuel shut off solenoid can cause this problem. The spring can become sticky, and occasionally stat shut when it should be open. How would I diagnose the solenoid?

 

The engine cranking on the starter would not be affected by a bad ignition switch in most cases.

Often what happens is the truck will stall or not start but radio and blower motor work but instrument cluster dies along with engine.

To test you could add a small light under the dash wired into the power side of the FSO,if the light goes out or does not light and all fuses are good then the ignition switch is suspect.

To test the FSO you can remove it from the IP,remove the snap ring from the bottom and extract the pintel and spring,then re-install the FSO body in the IP to prevent leaks-this is for testing purposes only since the FSO is the last safety measure to shut down the engine in case of an emergency.

If the gutted FSO solves the problem replace it.