The tank is 3/4 full, it has some powerservice in it, and some 2 stroke in it already.

 

That was the same darn problem I was having...Ran great in the city..On the highway different story..

Keep doing your tests..

 

Try what Bill mentioned...install a fuel pressure gauge...in the cab and check what happens when the problem occurs..

I did the same...My results...The pressure dropped to zero when the problem happened..Be curious if yours does the same...

 

I spoke with a guy at Miller's Diesel Service in NJ- a recommendation. He seems to think that because I was getting black smoke when trying to start, that I am getting fuel to the injectors. Therefore, he suggested that I could have a stuck injector, and compression is getting back through that fuel line to the pump. Any thoughts?
I just went and got the truck, after letting it sit about 2 hours. It was hard to start, and while cranking, it blew some black, then white, then black again. It took about 30 seconds of cranking, and it caught, but it then took about 30 seconds to clear out. It drove the mile home, but wasn't running up to snuff. I will get a fuel pressure gauge and see what's going on.

 

his 12v is doing exactly what my old 24V did when the lift pump went out- just starved my VP and made the truck undriveable Wouldn't his symptoms be the same on the P pump?

 

The temp supposition seems to be holding- I can go outside now, hit the key, and the truck fires right up and purrs like a kitten. I can run it all the way out to 2500, no hesitation, miss, or vibration. I will put a fuel pressure gauge on it tomorrow, a new shutoff solenoid, relay, and change the fuel heater screen.

 

It snowed/sleeted last night, and it's cold this morning. So, the truck will have to wait until later today or tomorrow.
I have been mulling over my conversation with JJ at Miller's Diesel Service. He suspects that I have an injector that is sticking, based on the black smoke at startup. What he explained was that when the injector stays open, it allows compression to flow back through the injector and injector line to the pump. This compression/air in the pump is what's shutting it down. It is hard to start back up, similar to having to bleed the system. Any thoughts? If I rule out a delivery problem before the pump, I guess it would be fairly inexpensive to pull the injectors and take them to a shop to be tested. Will an intermitent problem show up on the bench?

 

I always thought the fuel like what you describe followed the path of least resistance (pressure) back though the small return line on the injector to the filter, not back against the high pressure to the pump.

If you have over 150k miles on the injectors it would be a good idea to have them tested anyways.

 

The injectors have about 30,000 miles on them.
I spoke with Tom at Diesel Fuel Injection in Harrisonburg, VA, and, of course, he suggests first that I get a fuel pressure gauge going. He also thinks that my problem could be the overflow valve, and that the fuel pressure gauge will help in determining that. Given that the current valve has been on there for 130,000 miles or so, I may go ahead and replace it. It looks tight there- will it come out without loosening the pump?

 

Sometimes you have to file or grind the notch in the intake a little deeper to get the OFV out. Most come right out with no problem though.
Don't bend the line, it will be hard to get it lined up again.
Stuff a rag between the engine and pump so you don't lose the sealing washer.
The adjustable OFV here is best> http://fostertruck.com/Overflow_valve.htm

 

Ok- what I did today.
1) Replaced the fuel overflow valve with a new Bosch valve.
2) Changed the screen in the fuel heater.
3) Installed a new shutoff solenoid and relay.
4) Installed a fuel pressure gauge.

Once running, it showed about 22 psi on the gauge. Running it up, it would peak at about 35.
I took it out on the road, and it held 25 and up for about 6 miles. I noticed that it dropped down to 20, and power was down some. after about 7 miles, it dropped down to about 11 or 12, and had almost no response. It bottomed out then, and shut off.
Once I could get it to crank back up, it would only read about 15 psi. By the time I got it to the house (about 1/4 mile, it was reading about 10, and would barely run.
So, I guess that I have a delivery issue on the fuel side. I will replace the fuel filter for the sake of it, and look at an issue with the lift pump, fuel lines, or something in the tank. Any thoughts?

 

Didn't see it, when was the last time you cleaned the pre-filter? Also, take it for a run without the fuel cap on, see if it still does it to rule out vacuum for sure. I suppose it could be a lift pump, but I would bet strainer plugged/pre-filter/vacuum first.

 

I replaced the prefilter screen today, but the old one wasn't plugged- there was a little debris, but it probably didn't create a 2% blockage. It was pretty clear.
That's a good idea about the fuel cap- I will check that tomorrow.

 

Low Pressure Fuel System Diagnostic Procedures> http://dodgeram.info/tsb/1996/14-07-96.htm

 

does or has your lift pump made a Tick at idle? sounds like a blown exhaust header gasket- that's the sign of one going out