Engine won't crank... Sometimes.

[chawkins99]

Well, this is just weird!!!!
I needed to get my RV registered this morning...
The license office is about a mile from the storage facility so I fired her up (no problem), drove the mile to the license center. They needed to verify VIN and mileage and the guy was wowed by the RV and asked if he could hear the engine. Fired right up again.
Back inside, completed registration. Back outside. Again, fired right up.
Drove back to the storage and shut down while I unlocked the gate.
Got back in and it refused to start...
All the dash lights look normal. No alarms. Turn the key and NOTHING. It's not even trying to crank.
Batteries all OK. Cranked up the genset just in case it needed more juice. Still nothing.
Tried the battery boost switch. Tightened battery connections. Shut off all battery switches and left it for a few minutes. Nothing seems to work.
By now, the storage manager is taking notice. Brings out a battery booster. Nada!
Found the ignition relay in the electrical compartment. Was identical to another in there so swapped them around.
He then suggests hot-wiring the starter motor. Fired right up.
Now I'm running late for work, so just parked up. Shut down, dumped air and leveled. Then figured I'd try again....
Fired right up!!!!
My suspicion is the engine or transmission is detecting a problem and refusing to crank but how do I find out what?
My Scangauge doesn't show any trouble codes.
Any ideas????
Cummins ISC 330 (2003).

[GreaTOne65]

Start with something simple, check all the grounds, take them off, clean them, put them back together and spray them with battery protectant.

[johnzuki]

More than likely a neutral safety switch was not quite making contact. Toy with those next time, might do the trick.

[chawkins99]

Originally Posted by johnzuki

More than likely a neutral safety switch was not quite making contact. Toy with those next time, might do the trick.

That sounds feasible. A couple of occasions in the past I have had the alarm chiming just as I pull away which quit a few seconds later. My thought on that was the parking brake sensor.

Where do I find the neutral switch. It's an Allison 3000 (I think). I have tried selecting/deselecting a gear and then back to neutral.

[dennis45]

Originally Posted by GreaTOne65

Start with something simple, check all the grounds, take them off, clean them, put them back together and spray them with battery protectant.

#1, loose connection at the starter
#2, faulty slave solenoid. Follow the pos cable back from the starter to find this smaller solenoid. You will see two small terminals which are energized when you turn the key to start. You should feel this solenoid click when you turn the key. If not, chances are it's gone south. You can test it by removing the Pos wire to the starter and energizing the small terminal to hear it click. If no click, you have an interlock problem and the solenoid is not being energized. Rare.

[deandec]

I had similar episode last summer. After switching out the ignition solenoid, I discovered accidentally that the solenoid ground was gone. Created a new ground all was well.

The clue was that the ignition fuses did not power up when the key was on. The ignition solenoid ground was the fix.