Safety switch, blade disengaged, shifter in neutral? Interlock?

Walt Conner

Post the full, technical model number of the tractor. The number is found on a decal on the body under the tilting seat.
Once we know the full, technical model number, we can try for a wiring diagram online. The wiring diagram will have the details needed to troubleshoot the problem.

Also tell us what it DOES do when you turn the key.
Does the solenoid click? etc......

Thanks -the model number is: 917.270950 and it doesn't do anything when I turn the key-completely dead. The blade is disengaged and is in neutral. As I said, I can start it if I turn on the key and short across the the cables on the solenoid. Thanks.

I am posting one of my "stock" trouble shooter procedures for Craftsman starter control circuits, along with a wiring schematic to help (I hope). But be advised, the schematic is for model # 917.270951. I could not find an online schematic for 917.270950. But I found the schematics for ...941 and ...951 and they are identical (Craftsman are generally pretty generic within a group of model #s).
Also beware that my trouble shooter was not developed with this specific tractor as the case subject, but should be helpful as the wire colors and positions should be the same.
NOTE: Because you have replaced the starter solenoid and the key switch, tests of those components has not been included, but testing of the White wire at the key switch needs to be done anyway to check for a damaged wire terminal.
You have not mentioned whether you checked/replaced the main electrical system fuse. A blown fuse might result in the condition you are having, provided the engine DOES NOT feature a fuel solenoid on the carb.
Make certain the fuse is good before doing test procedure.
The procedure is for a tractor that has "manually engaged deck blades".
Procedure:
It could be a "bad clutch/brake switch", but it could be a "bad deck interlock switch" just as easy, so let's do some testing first. You have a volt meter and/or 12V test light? Be advised that moving or wiggling wires while doing these tests could result in continuity being accidentally restored AND this might cause the starter to engage when you don't expect it to. To guard against this, unplug the small WHITE wire from the starter solenoid and cover the wire terminal with tape to prevent a short while the tests are done. First off, you will need to access the backside of the key switch.
Step 1. Find the WHITE wire on the back of key switch connector (it is switch terminal S). (leave the connector attached to the switch) While holding the key in the start position, probe the area where the WHITE wire enters the connector body with a test light or a volt meter. You should detect voltage on the test light or the volt meter. If you do not detect voltage, replace the key switch (provided the main fuse is good). If you detect voltage, go to step 2.
Step 2. Locate the clutch/brake interlock switch (should be near the pedal or close by, switch must be attached so pedal linkage can operate the switch. This switch will feature 4 wires, 2 will be WHITE. With the key in the start position, and the pedal locked or held down, probe the WHITE wires of the brake/clutch switch. If you detect voltage on one WHITE wire only, make certain that the switch plunger is actually moving in far enough to operate the switch. If the plunger is moving far enough to operate the switch, but you still detect voltage on just 1 WHITE wire of the switch, replace the clutch/brake switch. If you detect voltage on both WHITE wires on the clutch/brake switch, go to step 3.
Step 3. Locate the Attachment clutch switch interlock switch on the deck. With the deck in the OFF position, probe the WHITE wires while the key is held in the start position. You should detect voltage on both WHITE wires. If you detect voltage on one wire only, examine the mechanism that operates the switch to make sure the switch is being moved by the engaging of the deck. If you find the switch is being operated when the deck is engaged/disengaged, replace the switch. If you detect voltage on BOTH WHITE wires at this switch, go to step 4.
Step 4. Go to the WHITE wire that you took loose from the starter solenoid and probe the wire terminal while the key is held in the start position. If you do not detect voltage here, the WHITE wire leading from the deck switch has a break in it somewhere.
If you do detect voltage here, reconnect the WHITE wire to the solenoid and turn the key to start. If the solenoid still does not operate and engage the starter, the ground path for the solenoid may be inhibited by rust or corrosion. If the solenoid has a small ground wire (4 post solenoids only), the ground wire might be defective.
If the solenoid DOES operate now to engage the starter, you have probably restored continuity at some point in the WHITE wire circuit by the actions of your testing (wiggling wires).

The seat switch does not inhibit cranking on this mower, it only functions to kill the ignition spark.
Malfunctions in the PTO switch or the clutch/brake switch are capable of inhibiting the starter.
I hope this helps in troubleshooting the interlock circuits.

{{gwi:315641}}

This guy probably read the above reply and went running to nearest big box store and financed a new tractor.

You might be right WB.
Troubleshooting is soooooooo expensive and it don't cost nuthin to replace a tractor if it hiccups.

But then again, after guessing at a solenoid and a key switch to no avail, what the heck, let's get a new tractor.

Uhhh, WB, did you delete your helpful contribution to that thread cause I can't find it anymore?

This problem could be all the things mentioned by the others. Here is another idea that was not mentioned. I have experienced the same problem and the solution was very simple.

When the key is turned to the crank position, battery voltage is sent to positive spade on the starter relay. A common wire (ground) is connected to the second spade on the starter relay. On many of the Craftsman riders, this common wire is connected to the frame with a sheet metal bolt located over the right rear tire. I have found secure bolts holding the wire tight, but no connectivity.

If this is the case, find the wire, wiggle the bolt with a wrench and tighten down.

Hasn't anybody noticed that this is a 3 year old thread?

Along that path blue, I had a YTH20K46 last year that would not crank w/o the headlight ground from the harness in front connected.

Yes Bill, I noticed right away it was an oldie.
But I took the bait anyway :^)

Hasn't anybody noticed that this is a 3 year old thread?
==============================
missed that. old eyes don't see very well

Is Walt still around?

Thank you Mownie for the awesome troubleshooting guide! Took me a few minutes to figure out where everything was but in the end it walked me through to a corrupt ground being my problem.

And Thank you Bluemower, I couldn't figure out where my corrupt ground was until I read your post about the ground bolt under the right rear tire. Snugged it up and my tractor is good to go again.

I appreciate all the help! :D

It is always good to learn that someone did find a solution by using the suggestions of the members of the forum.
It is difficult to quantify or explain all the reasons WHY we do this, but for me, it is basically just that I have a big mouth and don't mind helping folks out.
Glad it helped and thanks for letting us know. :^)

Ran good until it got hot. Back fired and stopped running. Turns over but won't start. Has blown clouds of white smoke in the past and quit running. After it cooled down it would start but now it won't. I changed fuel filer and spark plug. Nothing yet