I have a Murray GT garden tractor with a Briggs and Stratton 18 HP apposed twin cylinder engine.
Engine numbers:

Model: 422707
Type : 1525 01
Code : 9311175A

The key will start the engine but will not shut it off. The battery also does not charge. (its a good battery) All the safety switches that I can see are hooked up and there are no loose wires

 

Most likely a connector or ground has stopped making contact. I would start at the connector on the back of the key switch. Remove the plug, look for any dirt and or corrosion and clean. Check to see if any of the terminals inside the plug have pushed out of the lock. Follow the main wire harness and check other connectors for the same.
The engine schematic won't be of much help. If you post the #'s of the tractor, someone might be able to find one for the chassis.

Does the fuel solenoid shut the engine off? I think part of the grounding loop links to the solenoid as well so I would check the connections to and from it also.

 

What is the fuel solenoid? I know about the solenoid through which the battery and starter go through but I never heard of a fuel solenoid.

 

How do you get the engine shut off if the key does not do it?

If your engine has a fuel solenoid it will be threaded into the left side of the carb body and have one or two wires coming from it.
When the key is turned off the solenoid releases a plunger that physically stops fuel flow through the carb.

You can look at an Illustrated Parts List for your engine here
http://shop.briggsandstratton.com/BShopProductListingPage.asp?MecID=100&CatalogID=56B2B9A7-283C-11D4-8886-00B0D0203414&SessionID=43C7B3A0-6A44-4EB2-B2CC-23B437198A68&SMSID=Smart+Search&ViewName=htsDIY&EngineModelNumber=422707&EngineType=1575#

 

I don't think my engine has a fuel solenoid.

Anyway, I've been shutting it off by throttling all the way down, choking it and then engaging the snow blower. Probably not the best thing for the engine

 

According the to the Briggs drawing you should have a carb with a 3 screw fuel pump. The fuel solenoid is just behind the fuel pump on the left side. It looks like a single spade terminal connection. It should be the only wire going to your carburetor.
It could also be in the key switch itself if not the connections I already mentioned.

 

I didn't see any wires going into the carb other than the throttle and choke cables. Even if my engine did have a fuel solenoid, thats not the way an engine should shut off. Could cold weather have anything to do with my problem? All winter the key would not shut off the tractor. When the weather warmed up for a few days, then it did work. But now it doesn't.

I have a few tractors around my yard with key switches. How do I know what kind of Keyswith I need? Does it even matter?

 

Here is a list of components related to the kill circuit: 1- Single black wire running from the ignition coil to a junction block. 2- A wire (color would be unknown without a unit schematic) running from the junction block to the key switch - to the "M" terminal and is likely part of the harness and therefore difficult to pinpoint. 3- Possibly, a third wire running from the "G" terminal of the key switch to a ground point on the chassis (this would be necessary if the key switch is mounted to plastic rather than a steel dash panel. With this circuit known, you may have trouble with one of the two wires not making a connection and completing the needed circuit or at the key switch. It is likely the switch. Pull the switch out of the dash and using a test meter on "continuity test" you should have continuity between the "M" terminal and the switch body (or "G" terminal, if required) with the key in the "OFF" position. You can perform this test with the switch still mounted but it is usually difficult to read the terminals designations without removing it.

 

Come to think of it, I used a lighter on the keyswitch to un-freeze it several times in the winter. The key switch is very hard to access (requires steering wheel and dash-board removal). So I want to replace it. How do I know what switch to replace it with?

All the wires that Puey61 mentioned are in place.

 

I think I would remove the key switch, find a local Murray dealer and take it along with the model # of your mower, which you should find on a label on the rear of the mower.
If you post those #'s here Puey can most likely find you the correct part # for more purchase options.
Just in case your curious, inquire this part # should you contact your dealer...
Briggs part # 397266
Good Luck

 

The tractor is a Murray GT

Model Number: 42170x9a

date: 0614

 

Part number for the switch is 092377MA and can be purchased at a Murray/Briggs & Stratton dealer. Or, I'm sure, online somewhere.

 

Actually, the problem turned out to be the kill wire to the coil. Somehow underneath the shroud it got dis attached. Odd though because I just put that coil in not to long ago. Anyway, thanks for your help.

 

Good news. Does the wire terminal seem to have enough drag so that it stays attached?

 

Yes, I carefully crimped it with pliers so it isn't loose.

 

Enough slack in the wire so that the slightest tug on the exposed kill wire doesn't pull it off?

 

There is plenty of slack. I fixed this at least a month ago and have had no trouble since. I just thought I'd finish this thread.