Isuzu turbo diesel fuel system trouble shooting.
More questions, of course. Plus a few observations.
Looking at reasons this engine might run with the key off.
My execution of Acy76's suggestion to block the intake had a few flaws, now that I look at where I tried to block the intake. I opened the rubber pipe from the air clearer to the junction where the valve cover vents enter the intake. Bad idea on my part. I was only stopping the air coming from the cleaner. With this blocked air can still be sucked in from the top of the engine. This explains why this only slowed the engine down. If the engine was running on blow by from the crankcase this method was still letting that oily air in.

This time I opened the rubber duct directly connected to the turbo. I checked for excessive oil in the tube. There was some, not a lot. The inside of the rubber pipe was clean on top with a dab of oil on the bottom. I don't know if this suggests normal blow by. I will monitor the vents when I start it next time. This engine has 100,000 miles on it with the last few hundred driven at night by a woman who was unaware of the engine troubles the person who sold it to her had.

Another idea about this engine running post ignition (switch shut off) might be attributed to injector pump pushing too much fuel. I went over the fuel cut off solenoid to make sure it was working properly. There are two wires going to the solenoid. On the schematic it shows two wires going in, but only one activates the coil. Which one is it? Other solenoids run one wire to the solenoid case for a ground. Is this the case here? I don't see a ground on either wire, but I will double check this. I would like to remove the fuel shut off solenoid, but it is hard to get to, under the battery bracket. I put a voltmeter on it and with the key in the glow plug on, pre-starter mode, there is no power to either wire. It may be that I am not getting the probes in well enough. I can't reach the plug very well. I can probably get the plug off without removing the air conditioning compressor and test to hear if the solenoid is clicking by applying power to the leads. Is this advisable? Is the solenoid 12 volts? Can I hear it engage?

My train of thought here is, if the fuel cut off is working, oil is not leaking into the intake from the turbo oil seal, and the blow by is not excessive, then I will look at injector pump timing. A friend who owns a sawmill with lots of diesel equipment and experience said that diesel engines sound awful when they are running extremely rich. When this engine begins to run on its own, it sounds great, except for what I can only describe as a rod knock. There I said it. I cringe to think about why a gasoline engine might sound like this. Diesels I have little experience with. Anyway, if I can adjust the injection pump timing to less rich I will. But first I need to get all the other things done which might be causing this engine to run on its own. I still need to figure out a way to check the oil seal in the turbo.

This is the most difficult way to trouble shoot; not knowing what the engine was like before the timing gear came loose from the crankshaft, nor knowing what stuff the last mechanic(s) screwed up, nor knowing what happened to the engine while it sat in the Albuquerque desert sands for half a year.

These are all gray areas which I need to narrow down, if not completely eliminate.
In summary I would like advice on:
1> Turbo oil seal testing.
2> Fuel cut off solenoid testing.
3> Injector pump timing.
I know more than I did this morning. However this is not enough to trouble shoot with. Have I left anything out? What else might cause the engine to rev uncontrollably with the key on or off?
Please help if you can.
Sincerely,
Brian Rodgers <img src="/forums/images/graemlins/baby.gif" alt="" />