Diagnosing fail-to-crank - Craftsman GT-6000

dglambert · Dec 28, 2021

Tractor is a Craftsman GT-6000, 917.257740

Battery reads 14.6v, but the tractor fails to crank by the ignition key.

When I apply battery voltage to the starter solenoid trigger terminal (below), the starter turns the motor over, so I believe starter and solenoid are both ok.

Based on this, I expect the problem is in the ign switch, pto switch, or an interlock switch. The seat switch is jumped - when I bought the tractor, the seat had been replaced, and I don't see a spot to rea-add a seat switch, but the interlock bypass has worked in the past. The schematic (attached) indicates a brake / clutch switch, which I found (really tucked into a difficult-to-reach spot), and it seems to test fine -- open when the brake is off and closed / continuity when the brake is depressed.

Am I missing anything obvious, or am I down to the PTO switch or ignition? Any tips to test either or both of them? On the diagram where it shows circuits (ex: C + G for PTO off), does that mean I should see continuity across the C & G terminals? I guess that's the next step in diagnosing this.

tomplum · Dec 28, 2021

SO your Key switch, PTO and brake switches are in the crank circuit. Seat is not. I assume that your solenoid has only 1 small terminal on it? Commonly I would check for battery power to the key switch to start with. Look for terminals at the fuse and ignition switches especially that may be corroded. Then test from the switch S terminal and follow that if you have to from there.

dglambert · Dec 28, 2021

tomplum said:
SO your Key switch, PTO and brake switches are in the crank circuit. Seat is not. I assume that your solenoid has only 1 small terminal on it? Commonly I would check for battery power to the key switch to start with. Look for terminals at the fuse and ignition switches especially that may be corroded. Then test from the switch S terminal and follow that if you have to from there.

Correct - one small terminal on the solenoid. I checked the fuse itself, and it's fine -- I'll start looking for corrosion next. Thanks.

Kernopelli · Jan 4, 2022

I have the same lawn tractor and had the same issue this spring. Turned out to be corrosion on one of the ignition switch terminals. Cleaned it up as well as possible and problem went away for a month or so. Ended up just replacing the switch with a $10 unit off Ebay.

dglambert · Jan 5, 2022

Kernopelli said:
I have the same lawn tractor and had the same issue this spring. Turned out to be corrosion on one of the ignition switch terminals. Cleaned it up as well as possible and problem went away for a month or so. Ended up just replacing the switch with a $10 unit off Ebay.

I have a feeling I've got the same thing going on. After pulling all the connections apart and testing the ign switch and PTO switch (both tested ok), I re-assembled and it turned over just fine. So, it's working now (good), but I don't know which connection was corroded (bad).