Case 1850k dozer won’t start with key

[sundanceexp]

I have a 2006 case 1850k, it won’t start with the key, but if you hold the key in the start position you can jump the starter and start it. I had case come look at it and they said it was the starter relay so I replaced that, at $500 and same issue, if I jump the poser going into the starter relay to the wire going to the starter it blowers the operator safety relay fuse in the cab. I have a service manual for it, but the wiring diagram is pretty much useless. I am hoping someone on here has had a similar problem and hopefully knows what’s wrong, or something. Please help, I hate to scab it and put a push button in or something to bypass factory wiring, but maybe that’s my option, as I can’t find anything that stands out as wrong.

 

[Tinkerer]

I cannot help you, but there are 3 different variations of the 1850K.
Tier 1, 2 or 3.
A serial number would help.
What did the mechanic say when the relay didn't fix the problem ?

 

[Travs Thompson]

I have an older case backhoe that the key switch would not trip the relay to engage the starter. I replaced the key switch and it worked again. I figured that the key swtich was worn out and not sending the proper voltage back to the relay to trip it.

 

[sundanceexp]

It’s a tier 2. Mechanic was baffled. The wiring diagrams in the service manual are pretty lacking. We don’t have much for service around here, the case IH dealer bought all the construction stores and didn’t keep anyone that knew anything.

 

[Tinkerer]

Might be a transmission neural start safety switch problem.
Can you scan the electrical schematic and post it here ?

 

[sundanceexp]

 

[sundanceexp]

This is out of the shop manual, only other diagram is of the panel, but it doesn’t show anything. There is power from key switch to the relay, relay should be normally open but is normally closed as long as it’s hooked up, if you unhook wire going to the starter then it becomes normally open, if I try to jump from power coming to relay to starter it blows the fuse. I’m guessing there is a short somewhere. Maybe CNH has a better wiring diagram

 

[sled dog]

Something doesn't sound right with that relay, and where you are trying to jump from. Can you carefully explain again where you are jumping from to the starter?

 

[Tinkerer]

I doubt that Case has anything better than what is in the service manual.
Can you hear or feel the relay opening or closing when give it power or remove the power to it ?
Yes, a short or possibly a loose wire harness plug if there is one in that circuit.
It is not unusual for those connectors to corrode and cause problems- if there is one in the circuit.
Does the tachometer have a digital display that would show fault codes ?
Hopefully one of the HEF Case Pros will read this and offer you some real help.
Like Sled Dog, said something does sound right with the relay.

 

[sundanceexp]

I swapped the relay out for a brand new $500 case relay and it does the same thing, definitely not the relay. There is actually two starter relays and the other one tests good, I even switched it out with another known good relay. I tried to jump from the wire that gets power when you turn the key switch to start over to the wire going to starter solenoid. I can jump the starter if I hold the key to start and make it start as long as I disconnect the wire going to starter solenoid from relay

 

[sundanceexp]

No codes that I can get. The tach is mechanical but has digital hour meter. I can’t believe there isn’t a wiring diagram of the entire machine somewhere

 

[mekanik]

Which posts on the starter are you jumping when it starts? When you turn the key to the start position is the starter solenoid making a fairly loud click?

 

[sundanceexp]

Yes the relay clicks

 

[mekanik]

You are shorting the two big posts on the starter solenoid together to start it?

 

[sundanceexp]

Jumping from hot leg on starter to start wire on solenoid

 

[mekanik]

If you are shorting the two big posts on the solenoid I suspect the solenoid has failed. When you turn the key to the start position the solenoid pulls the pinion into mesh with the ring gear. Once fully engaged there is a plate in the solenoid that connects the Battery post to the start post on the solenoid. It sounds like to solenoid is pulling the gears into mesh but not closing the circuit to send power to the starter motor. The posts and plate erode over time from making and breaking a high amp load. I'm thinking a new solenoid or starter is in order.

 

[Tinkerer]

Jumping from hot leg on starter to start wire on solenoid

Classic example of a defective solenoid.

 

[sundanceexp]

I don’t believe it’s the solenoid, as the start wire going to solenoid has a connection in it, and I can disconnect it there and use that wire to go to the hot leg of the starter and make the engine start as long as I hold the key in the start position. I’m not getting power to the solenoid by turning the key, but if I feed the solenoid 24v from battery it will start. Unless I’m missing something ?

 

[sled dog]

Classic example of a defective solenoid.

Tink, I don't think so. The start signal is not making it from the start relay to the start signal wire on the solenoid. IF, and only IF, the relay is working as it should, it should send power to start terminal on the solenoid

 

[Tinkerer]

For sure Sled Dog.
I was dead wrong about a defective solenoid.
The relay in the circuit is whole different situation from one that doesn't have one in it.

Seems weird the power wire that energizes the solenoid comes from the relay.

It seems odd that shorting the small terminal on the solenoid to the bigger one will start the engine. Evidently good voltage is getting to it from the relay.
Could it be as simple as a bad connection or connector on the that small terminal ?
Or the stud that goes into the solenoid is defective inside the solenoid ?