The timer is working correctly and has nothing to do with engaging the starter. Testing this control plugged in can confuse you. Your wire colors and functions should be this. Green goes to a coolant sensor. It is a ground circuit and applies a ground to the timer.This tells the glow plug timer control the engine temperature. If it is warm enough the controller wont activate the glow plugs. Red with a black tracer is a 12 volt keyed power source. The solid Red applies a ground to the glow plug relay. The Orange with a white tracer goes to the starter solenoid activation wiring. I am pretty sure when the tractor is normally starting when voltage is applied it cancels the glow plug timer function. The way you describe it right now I believe the timer is working correctly. If the colors I told you here are correct I can coach you the rest of the way. I think. [lol].

YES !

Lets do it this way. As far as I can tell the Orange with the white tracer goes from the solenoid to the brake switch. At the brake switch it changes to a Orange with a black tracer. From the brake switch the Orange with a black tracer goes to the PTO switch. At the PTO switch it changes to Orange and goes to the Ignition switch. So for it to crank the ignition switch in crank mode applies 12 volts to the Orange which then goes to the PTO switch. The PTO switch tells it the PTO is disengaged and now sends 12 volts on the Orange with a black tracer to the brake switch. The brake needs to be applied to then switch the 12 volts on the Orange with the white to the starter solenoid. I would start at the switch and verify it is sending 12 volts on the orange and go from there. The safety system shuts off the fuel supply so it may crank and not start. Remember these switches brake and PTO are multi function. You will see more that 2 wires at each switch as these switches are also part of the operator presence system and will cause the tractor to crank and not fire up or stall because the fuel solenoid gets turned off. Like I said start at the ignition locate the other switches and walk your way through it. Let me know know it works out.

i just printed out your reply.
thank you greatly !
i will now compare what you said to the diagrams i have, and run to the various safety switches in order, verifying a 12v presence.
the only thing i can add, is that by applying 12 volts at the timer wire, i have had the tractor running, so that "should" indicate the fuel solenoid is not being shut off.

and not to fear, when i figure this thing out, all will know what it turned out to be !

isn't edjumakashun fun ?
Thanks Again !

Right. That's why I was saying there are several functions going on through these switches and controls. The diesel only needs two functions to happen for it to start. Crank and fuel. One part of this system will shut off fuel if the parameters are not met and the other wont allow it to crank unless its parameters are met. In your case fuel is met and crank is not. Making it crank by applying 12 volts to the Orange with a white tracer was bypassing the safety switches. A hack will by pass the system and then allow it to become a death machine. Here is a story for you. Years back a friend had a 64 Plymouth Belvedere automatic with a healthy 440. I was in his garage and he started the car and it lurched forward as he quickly shifted it to neutral. I asked him what that was all about and he said he never wired in the neutral safety switch. I said man you need to fix that. He laughed. Story ends when I saw him months later and he tells me he was working on it and needed to bump the motor over. Well it fired off in gear and took the work bench out as it smashed it into the wall. Good thing he was hanging over the fender and not in front. Point is try to fix the tractor right.

I don't know if anyone covered this or not but most of these safety switches will control ground to the primary side of the control relay so you might not see what you are looking for when poking around with a meter or test light.

Kevin

how true. i have been looking at grounds, especially for corrosion or broken/chafed wiring.
what still gets me though, is while in the CRANK position, that timer module has 12 volts going INTO it on both the outer wires, while the center orange/white tracer has only 5.22 volts coming OUT of the module with the wire popped out of the connector [not attached to the timer module].

i'll figure this out if it kills me !

i certainly want to fix this thing RIGHT ! i have seen things that happen when a person gets caught in a PTO by accidental start up when the PTO is engaged, and it AIN'T PRETTY !

.
This is why I explained this to you. Forget about what you think you are seeing with the timer module. It is not a part of the cranking circuit. If you keep thinking the problem is there you will be like a horse with blinders on and missing the actual problem. Reason I say that is I have done exactly what you are doing.

ah HA ! your response finally sank into my feeble dumb mind !
i THANK YOU a LOT ! i believe the saying goes : "can't see the trees because of the forest". quite a lot of times, i fixate on a particular subject or object, then can't think of, or see, the whole picture.
i have hospital appointments later today, and "food gathering" for tomorrow, so saturday will be the earliest i will be able to apply your suggestions.
Thank You again for prodding my old mind into [somewhat] working again like it should !
as they used to say : "film at eleven !"
i'm not sure if there will be a film, and maybe not even at "eleven", but this problem will be found and the results will be told.

Let me know when you get back on it.

yesterday was a fun day, not because i didn't learn how the safety switches and associated wiring intermix with each other, but because i found [i think, or at least hope] what appears to be the problem.
i started by locating all the switches and removing them from their mounting positions to allow access for testing purposes, both in action, as well as to confirm the wiring colors and the voltage and ground functions.
if you think laying on your head under your car's dash looking at wires is a treat, this tractor is for you !
i started at the brake switch. the first thing tested was the switch itself. it tested ok in it's function, so i next had my buddy run the key so i could check what was coming through the plug for the switch. the first thing that became apparent, was the starter tried to engage without the switch being plugged in !
there are two brake switches in this system, and i removed the wrong one. oops ! removed the correct one, the switch itself tested ok as to function, but was not seeing any voltage flow from the PTO switch.
next, the PTO switch was checked for function, and appeared to be operating as it should. a 12v jumper was used to send power to the brake switch, and when the brake switch was depressed, the starter kicked to life ! this is starting to look promising ! the wiring to the PTO switch was checked at the plug. the finding was battery voltage was MISSING in the crank position. with a 12v jumper on the switch, the brake switch was depressed, and the starter operated.
so on to the ignition switch. it has four wires, two red with white tracers [being hot at all times], the wire next to them [not sure of the color] being the run wire showing 12v in the run position as it should, and the orange wire [going to the PTO switch] being the battery voltage source in the start position.
with the ignition switch plugged in, the start position showed intermittent battery voltage, but i wasn't quite sure i was getting a good reading. at times, i was getting 2.3v, and at others, i was getting 11.8. so jumping the battery voltage at the plug to the orange start wire in the plug caused 12v to be sent to the PTO switch, which in turn, supplied 12v to the brake switch, when depressed, spun the starter !
so possibly the trouble all along could have been the ignition switch ?
this switch had previously been replaced before i got involved, and luckily, my buddy kept the old switch. it is plastic, so i popped it apart and discovered it was kind of melty, then i remembered i had done this previously. i grabbed the switch that was being used on the tractor [plastic as well] and checked for continuity. it had a reading at every time i jumped the hots and the key was turned to run, but the start position was not consistent, sometimes continuity, sometimes not. i tore it apart. it seemed a little dirty, so i cleaned the contacts up and applied a little white grease. i rechecked the switch in all positions numerous times, and it seemed to operate as it should. wow ! success at last !
i plugged it back in, and it cranked ! ...... for about a couple of revolutions, then quit ! i checked the wiring at the plug, and was getting battery voltage at three of the four terminals in start, with the orange wire going to the PTO switch reading 2.2v.
when jiggling the switch while trying to get a reading, occasionally, i could get the starter to kick, but not function.

so now, i'm ALMOST convinced the starter switch is, and has always been, the culprit. with the switch being plastic, i'm thinking i should obtain a universal type made of metal and make up a new plug to fit it.

NITROUSN, your wiring colors were spot on, so that helped me tremendously !
what do you think about my ignition switch idea ?
it feels like i'm SO close...........

It sounds like you are on the right track. The ignition switch has 4 wires. Orange is the 12 volt crank wire sent to the starter via the pto and brake switch. The Red with the White tracer is your battery feed wire it should be on two terminals at the switch. It also should be protected by a 30 amp fuse. The Red with the black is your 12 volt key on function that should power most everything that is key power activated on the machine. What I would do if possible when it wont crank make sure the Red with the White is powered up in the crank position. If it is and the Orange is absent of power the switch is bad. Reason I say make sure the Red with the White stays powered as there is a splice were both of the Red with the White are tied together as they both feed the ignition switch. Sometimes a bad wire splice or terminal connection could loose power when a draw is applied. A lot of times you will get errant voltage enough to read on a meter or light a test light but disappear when loaded. One simple thing to check are the female spade connectors at the switch. Some times if multiple wires are in a molded plug they can be held rigid and not be pinching the male spade on the switch. Just maybe the other switch was replaced for that reason. Let me know if I can help you out further.

One other thing if you decide to get a universal switch you only need to use three wires as the Red with White will be the battery feed, Red with Black will be ignition and Orange will be start.

This is another clue to a connection issue at the switch. Over heated and melted is a sign of a poor connection. Like I said double check the spade connections. If possible remove them and squeeze them tighter and see what happens. Also watch the white grease best to use dielectric.

when the ignition switch is plugged in, every time it's operated the two red/white tracer wires have voltage, as well as the run/accessory red/black tracer wire.
the orange start wire is hit and miss.
the reason i used white grease inside the ignition switch is because that was what was in it when it was taken apart. i thought that was kind of odd because i expected di-electric grease.

as to the ignition switch connector, it is in perfect condition. the old switch was melted inside [luckily] and not the connector.
i think i might have an ignition switch around here to try. if so, i'll make up some jumper wires and plug into the switch connector to try it first before i cut the wires and wire it permanently.

It sure sounds like the switch. Just check the female spade to be sure. The old white lube still could of been dielectric.

i have never seen white di-electric, so i just assumed it to be white grease.
i'll take the switch back apart, clean it up again, and put in di-electric. i'll test it again, plus pinch the female terminals and retest, then see what transpires.

you have been a HUGE help ! i can't thank you enough !

No problem. You helped me with some of my car rebuilding questions, so I need to help you out. At least you are willing to look and listen to advice , where others don't give a rats behind.

i have repaired many, many wiring problems in the past, plus wired from scratch probably a dozen or so vehicles, but this is my first foray into a diesel tractor and it's many safety switches.
when this FINALLY gets fixed, i will report back. it might be a few days though.