my one buddy has a cub cadet tractor that has a 3 cylinder diesel engine. [i can't see anything on any tags who made this engine]
the problem is the starter will not crank over. battery is good, and all wiring from the key to starter/glow plug relay checks good, plus all grounds, starter, and starter battery cables check out as well with no voltage drop.
attached, is a diagram showing the glow plug timer preheat module. it has 12v on the outer top row terminals in run and start.
the center terminal shows zero volts in run, but only 5.22v in the start position. if 12 volts is applied to the center terminal, which goes to the starter solenoid [almost identical to a mini-starter], the starter spins over as it should, and the engine starts.
is this module bad ?
the wire going to the glow plugs [from the relay] has 12v when key is turned on, and after xx seconds, the relay kicks, voltage to the plugs turns to zero, and the dash light for the plugs goes out [as it should ?].
i know nothing about diesel starting systems. TIA !

See if you can jump the starter to get it to crank.. you could have a bad ign switch

Does it have any safety switches like a riding lawnmower?

There are forums for most brands of tractors out there, they might be able to give you more detailed info.
https://www.mytractorforum.com/threads/cub-cadet-diesels.97148/

I've used them for info when working on my 1954 Ford NAA tractor.
Lots of good useful info on the tractor forums.

When I bought my ford diesel tractor I bought all the manuals for it at that time.. same thing
when I bought my crawler loader

Not knowing what model your tractor is I can only tell you what I know about my Kubota. Most small tractors under 40 hp. have a system called OPC. Operator presence control. I had issues and it was all related to a seat switch. The kubota has several switches mainly on the seat, pto, and hydro pedal. They all can cause no start and shutting down. I would do some checking to see what system his tractor has. Also check the fuses as when mine was acting up I accidentally blew the OPC fuse and then it would not crank. Replaced the fuse and then diagnosed it to the one seat switch that was not registering some one in the seat. Mine also had a second seat switch so if you flipped the seat up over the wheel the switch would allow the pto to run with out an operator in the cab. Rear pto implements like a rear 3 point log splitter or chipper. Do some research on that system.

On my Cub, not a diesel, if the brake pedal isn't pushed all the way down it won't crank, if the PTO switch is "ON" it won't crank, if you're not sitting in the seat it won't crank.

Thats the way my zero turn is... I jumped 1 of those switches

thanks for the responses guys !
i forgot to mention, when the key is turned to start, the solenoid clicks and you can see the starter gear jump toward the ring gear, but the solenoid wire at the starter is only receiving 5.22v, thus acting like a dead battery, just enough volts to excite the starter, but not enough voltage to turn the starter motor over,
when a full 12v is applied to the solenoid wire, either by jumping the hot lead at the starter connection to the solenoid, or applying 12v to the solenoid wire at the timer module [where the 5.22v originates], the starter works as it should.
that leads me to believe the tractor battery is good and the safety switch[es] are working. i would think if any of the safety switches were bad, when the key switch is turned to start, there would not be any voltage [no matter how low] sent to the starter ? i have the starter switch hanging, and it puts out 12v in both the run AND start positions, while in the run position, the start position has NO voltage present.
i did a quick check of all the fuses at the beginning of this ordeal, but i will go back over them to see if dumazz me missed something.
i also have jumper wires made up to bypass the safety switches.
as i have said, this is my first go at a diesel tractor, so i know nothing about it.
i hate to spend anything on a factory FSM to never use it again. if it were my tractor, i would have bought one as soon, or shortly after, i bought the tractor.

thanks again for the suggestions guys ! please keep 'em coming !

What model is it?

Forget what you think you know when it comes to these tractors with computers.

A place I used to work at had Kubota tractors that used to do the same thing. On them it was corrosion in the clutch pedal switch.

You need to go upstream with a voltmeter until you find your issue. It will either be a corroded switch or section of wire.

How does this little controller interact with the glow plugs? It sounds like the glow plug relay/light are completely separate from it? Is this box supposed to prevent cranking unless the glow plugs are warm?

Is this box big enough to hold a relay? If you're only getting 5v out, I would assume that it's bad...

7264

the box only measures 1 1/4" wide x 1 1/2" long x 1/2" thick [not counting the area for the plug. it also has some kind of potting material on the back, sort of rubbery consistency, or i would have taken it apart by now to see what's inside.
the tractor has no computer that i know of, looking at the wiring diagrams i have.
as to how it interacts with the glow plug relay, that relay supplies the two outer [top row] terminals with battery voltage at all times [in both run and start].
in the start position, at anytime, the center terminal [going to the starter solenoid] you can get a voltage reading regardless if the glow plugs are warmed up or not. this voltage is enough to kick the starter drive gear toward the flywheel, but not enough to get the starter motor operating. yet when you apply battery voltage to the center terminal, the starter motor works as it should !
there are no other wiring sources connected to either the glow plug relay or the timer gizmo that i can see from the diagrams.

i'll have to look closely at the clutch/brake switch the next time i get out there.

this gotta be something simple. i just have to find it.

It sounds like the glow plug sensor is bad.. I think if it doesnt read a certain temp it wont let
the engine to crank and fire up

I'm begging to think there's something bad in that box you pictured

I'm just curious why it would have two pins that take the same Run/Start signal

me too, but they are from the glow plug relay, which "seems" to be functioning correctly.
i'm almost ready to just install a pushbutton starter switch run through a relay.
that box was quoted by the local cub cadet dealer at $165.80 !!
i did a quick search on line [the bag] and couldn't find anything remotely close to that box at all.

A pushbutton is starting to sound pretty good

My tractor has a box to trigger a solenoid to cut off the fuel and turn it off when you turn the key off. It died, and a tractor junkyard wanted ~$250. So now I have a string that goes to the injector pump to pull a lever to cut the fuel off

The small wire you are applying 12 volts to make the starter crank is it Orange with a white tracer.

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.

it has been a couple of weeks since i have been able to get back to this tractor.

as i thought i had the "no-crank" problem traced finally to the ignition switch, i concentrated on seeing what i could find out what exactly was wrong with it.
after many times taking it apart and watching it go through it's motions, i discovered the plastic housing was distorting just enough to lift the internal contactor from the 12v feed strip in the start position.
one $8.99 universal three position metal ignition switch later, and it's ALIVE !

a GIANT Tip O the Hat to member Nitrousn for walking me through the myriad of safety switches involved with this tractor and their function, which prevented me from spending big bucks for things i didn't need !
THANK YOU SIR ! MOST GREATLY APPRECIATED !

Glad to hear you got it running and a cheap fix

No problem at all. Once we took your blinders off, I was able to help you because you were willing to listen and look as instructed. Really not a complicated system just mis-understood. I owed you anyway for helping me on my car questions with your helpful photos.