Took the GPs out because I was advised with a hard starting problem, to routinely remove the GPs and GP controller; I do not like replacing-replacing-replacing when I don't know what's wrong. I ran some new electrical tests today, here are the results. They were all WARM tests, with the block heater on all day. Tomorrow, I will run cold tests, electrically.
Oh! It always started with the heater on, though it took 3 times of long cranking, and when it started, it ran very SLOW RPMs building up gradually. Today, it wouldn't even start with the heater on all day, nor would it start with ether. Formerly, it would not 'fire' (rattle) when I tried to start, just dead/flat cranking. It is rattling like crazy like it wants to start, but no start. I suspect air, but don't know what to do to diagnose? I already ran lines direct from gas can to filter with electric pump in the middle...and from IP return line to a bottle, and kept both lines full of diesel. Same hard start. As for the filters, I replaced the canisters and re-tightened the fittings when soapy water test showed air. The only line I haven't tested is the one from the last filter to the IP intake, most of it is metal and i did the soapy water test on the connector where the rubber attaches with a clamp. But...though I changed the return lines and replaced with 1/4 fuel hose + old spring clamps, I didn't change the plastic caps, and didn't notice any o-rings (it was before I read about them). No change.
OK, the electrical tests from today:
1. chassis to - battery (GND) OK.
2. Battery voltage today is 12.29. Reading with load is 11.5v while glow plugs are supposedly on and 10.9 while cranking (with GP supposedly on).
3. voltage directly to engine coolant temperature switch (red/grey wire) is 12.29v with Key On. With hot engine (block heater) resistance between terminals with key off is 18 ohms
4. With probe on - battery and other probe to GP cap, key on, while clicking, 2v, after clicking stops, 12.29v.
5. Found what I think someone told me was a glow plug connector/harness with 2 yellow wires on the fender and pulled apart. Looks OK, one side has 4 holes the other, 3 pins. The side with the sockets/holes, holding it with the mechanical latch face up, the upper right hole has 5v going to it, the lower left has perfect continuity to the GP cap.
6. With key off, and one probe to + battery, ...
A) other probe to the black wire on GP controller, same 12.29v to BOTH ends of the resistor. (ISN'T THE RESISTOR SUPPOSED TO STEP DOWN TO 10.5V?).
B) with other probe to other large lug on controller, nothing
C) with other probe to Control wires red and red/grey, also 12.29v
D) with other probe to the WHITE wire on controller, 12.5v initially, then 11, then 0, as it cycles.
Thank you for all your help. Any more advice about air, or electrical? (or anything else?). Any thoughts about the battery and starter? I disconnected the older battery and the other one is brand new with 1000 CCA and I still have no difference in attempt to start. The problem seems to be getting worse.
Forgot to mention, went on a 6 month trip and truck was only started once in that period of time, just before we returned, someone tried to start it, but a hole appeared in a rubber fuel line and diesel tank emptied out, they introduced air and couldn't start it for a long time, ether maybe? I don't know all of what they did? Stanadyne additive/lubricant. When we returned, we primed it, started it, and had some stalling, primed again, seemed OK until about a month or two later, with the extreme cold, hard starting, until now, no starting.