MAX IV - Engine won't turn off with the key

[tyson72]

I'm very new to all this, but am hoping to get some help figuring this out.

I have a MAX IV (year unknown...all the plates are spray painted over). It runs with a Briggs & Stratton 18HP v-twin. Starts great on the first turn of the key...doesn't seem to need much choke to start up and runs/idles/etc just fine.

The wiring was ok...but there was some splices/taps for a radio (long gone). I cleaned up the wiring and am pretty sure all the wiring up front by the ignition switch/hour meter/voltmeter is clean and pretty much back to "stock".

The issue is not being able to turn off/kill the engine with the key. The issue existed before I cleaned up the wiring...and persisted afterwards. Completely possible/likely I've missed something.

When I turn off the key, the engine keeps idling along as if nothings happened. If I play with the choke/throttle on the engine itself I can, most times, starve out the engine until it quits. Reading as many posts as I could...I did try to turn the key slowly, wiggle it as I turned it off, etc... to no effect

What should I look at next? I'm not an engine guy...so I'm not sure where to look/test. When the key is turned off...what circuit is interrupted (ground...+ve current, etc..)?

Is it as simple as these switches get worn out (the key/slot seems so worn that using a key might be optional...LOL) and just replacing it would do the trick? Could have sworn that it only had 6 pins on the back of it in a little triangle arrangement...but most references refer to a 7 pin..

Any help or pointers are much appreciated!

https://6x6parts.com/11004-ignition-...ls-max-iv.html

********EDIT*******
Found this post... http://www.6x6world.com/forums/argo-...-turn-off.html
I'll check that out tonight and see if I can find a loose/bad connection. Nervous to poke around randomly not really knowing what I'm looking for...LOL

[dirtdobber]

Welcome to the site Tyson. The way the kill circuit works on many of these small engines is by grounding the coil. I don't know exactly what engine/wiring you have, but generally, on older engines with no pressure switches and such, there are three wires that come from behind the flywheel and exit through the sheet metal housing somewhere. Two of these wires should plug into the regulator/rectifier. The third should be the ground wire for the coil.

When the key is in the "off" position, it completes a ground circuit to the coil. So, the switch will have a wire that goes to ground somewhere, and it will also have the kill wire coming from the engine. Either the switch is bad, the ground is bad, one of the wires/connectors is bad, or I'm completely wrong on how your engine is wired!

Good luck. A multimeter is your friend in these cases. Continuity tests are very handy.

[tyson72]

Thank you! It'll be headlamp, multimeter, scrap paper and pencil time this weekend. I'll check the engine kill wire first, then the switch, then rip everything out and climb in to chase the wiring loom if that doesn't work. Tys

[ARGOJIM]

Vanguard engines have a post on the upper front side of the tin, either a stud or a spade, most Max have a white bullet connector. Check that either style of that is connected, it so try to ground that directly and engine should shut down. If so in wiring, it not internal.

[tyson72]

Thank you both for the pointers! For a "never messed with this stuff newbie" the straightforward help is much appreciated!!
(Should have taken pictures...)
So I found the stud on the engine (it already had a black wire connected to it...tight...that went back into the wiring loom and eventually back to the ignition switch)..while the engine was running, I took a length of wire...wrapped it around the little stud on the the engine and touched it to the chassis...that killed the engine right away.

I used my multimeter and did a continuity test from the ground pin (black wire on the ignition switch....I do have a 7pin switch, the little one off to the side isn't used) and it confirmed continuity from the wire at the ignition all the way back to the stud on the engine that I used to ground it out. Checked both the end of the black wire that goes into the plug that attaches to the ignition switch and the terminal on the back of the switch itself...both ok. If I'm figuring things right...since there's continuity in the wiring, I don't need to take the wiring loom apart.

I tried to jiggle/wiggle the key as I was turning it off...but no luck killing the engine with turning off the with the key.

So.....best I can figure it's an issue inside the ignition switch itself where it's not completing the ground circuit? I found one on Amazon.ca (I'm in Ontario Canada) and it looks just like the one on 6X6 Parts. I'll order it eventually and swap it in. I was tempted to take the ignition switch apart to see what's going on inside of it...but didn't want to do that unless I had a spare to swap in in case I couldn't get it back together.

But for now I wired in a kill switch that sits with the gauge cluster/etc, so now at least I can start the engine and kill it on demand. I used a racing car/fighter jet kill switch with bright red cap that flips the switch to kill the engine when it's swatted down. The kids think it's funny...one can't wait to drive it...the other said that she's not getting into it but will take a video when I drive it into the pond and start sinking...LOL.

[Millar]

Hi had same trouble with response you may have to put a couple of diodes in the wires that run from the coils hope this helps

[tyson72]

Since the old switch looked...really old (it was so wore out that I'm surprised that the key actually stayed in...LOL) I bought a new one and swapped that out. No change shutting it off by key. So for now I'll leave it with the kill switch in the dash and wires routed around to the little ground stud on the engine. Some of the gauges weren't working either (or suspect) so I swapped those out too. Now I have a little switch to turn on/off a voltmeter and hour-meter, and a kill switch that will stop the engine. I'll bash around with it in the spring before I redo anything else.