# '81 MTD lawn flight won't start



## RoadRanger (Dec 5, 2011)

hey guys, figured i would hop on the forum and see if anyone can help me out. 

i've been trying to figure out why my old MTD lawn flight won't start. the tractor is roughly from 1981, has a 11 HP briggs single cylinder engine. 

i was thinking something fried in the ignition system, as the tractor was running well then after being shut off would not even try to crank over. not even a "click" when the key was turned, just dead. i replaced the ignition switch figuring the corroded terminals were the cause but no luck. 

i also tried to jump from the battery (which is charged) directly to the starter with a peice of wire, and the tractor cranks over great but won't attempt to start, which leads me to beleive there is a short somewhere in the ignition on / off circut.

problem is i've got no real idea on how to figure out where the problem would be, the wireing has got me a little bit stumpped.

can anyone help clue me in?


----------



## Country Boy (Mar 18, 2010)

If the engine is a Briggs, then the engine numbers will help determine what ignition system you have and how old the engine is. Briggs uses Model, Type, and Code numbers that are usually stamped into the metal shroud over the flywheel. Locations can vary, but if you find them, please post them. The Code is the date and manufacturing code of the engine. The first two digits are the last two digits of the year of production. The next two are the month, and the last two are the day. There may be two more digits at the end, but those are plant codes that aren't relevant.

As for the starting problem, first see if there is a fuse in the system anywhere and check it. Next, locate your starter solenoid. It can be found by tracing the Positive battery cable from the battery to the engine. Its usually a small metal or plastic box or cylinder that has two large wires attached to it and one or two small wires on smaller terminals. The large terminals are your load terminals. The small terminals are the control terminals that activate the solenoid switch. If you have two small terminals, then one is ground and the other is power. If you only have one, then it is power and the solenoid grounds through the chassis. Try jumping power to one of the terminals and see if the solenoid activates and cranks the engine. If not, try the other terminal. If neither one does anything, then the solenoid is probably bad. They are pretty cheap and usually not too hard to replace. Just hook up the wires the same way they came off.

If the solenoid works, then you need to trace the problem further. The key switch generally gets its power from the battery side connection on the solenoid. There usually is a small wire on one of the large terminals that goes to the key switch to provide power to the switch. Use a test light or multimeter to see if you have power to this terminal. Next, one terminal is the starter terminal. It may be labeled with an S stamped into the terminal on the switch. That terminal provides power to the safety system and then to the starter solenoid. If there is power there when you turn the switch to "START" then the problem probably lies in one of your safety circuits. Most mowers have a starting safety circuit that includes the clutch switch and the PTO switch or lever. The PTO must be off and the clutch depressed to start the unit. Try bypassing each switch in turn to see if one is bad. If that doesn't help, then there may be a broken wire somewhere in the system.

As for your engine kill system, there is usually a black or green wire coming out from under the engine shroud and going to a plug or terminal on the engine. Grounding that wire to the engine block will kill the engine. You can unplug that wire and see if the engine has spark then. Worst case scenario is that power backfed down the magneto kill wire and shorted out the magneto. I've seen that a few times when a ground wire breaks or falls off. Current wants to go somewhere, and it finds the path of least resistance.


----------



## steffler93 (Oct 30, 2013)

Did you get this problem sorted out? Haha ive just stumbled upon this problem myself and have no idea what it could be. Ive spent what feels like a lifetime going through every wire from everything and it wont crank over. Ive just replaced the starter, solenoid, battery, plug, battery cables, fixed head studs, new oil. Basically everything and anything. The motor has been apart for about a month and we got it to fire and run 2 days ago, but now its back to not firing. Solenoid and starter were changed tonight.


----------

