Picked up a lawn edger last week for $5 and because it was so cheap, thought it worth the gamble.
But before I start repairs to the frame and fit new wheels I want to get the engine to run.
It is a Red Briggs and Stratton 3.5 hp unit.
Is it OK to run a wire from the electronic ignition unit, through a momentary switch and to ground to stop the unit.
The old setup on the motor has been butchered and it appears to have gone through what looks to be a diode. Anyway with this all removed the engine has spark, but you need to choke it or pull the ignition lead off to get it to stop.
You need to post the information from the cooling air cowl - the long series of numbers divided into Model, Type and Code - before we can deal with your questions with certainty. The Briggs ignition system uses a "kill wire" which is always black, coming from the system. Whenever the kill wire is grounded, the engine will not fire. However in very old Briggs engines (prior to 1982) the kill wire comes from the breaker points, inside the flywheel. In 1982 and later engines the ignition is electronic and the kill wire comes from the Magnetron unit, a modified form of the coil unit found on the earlier engines, located outside the flywheel.
So, you need to locate the kill wire. We can help you do that if you post the series of numbers, plus you remove the cooling air cowl and post pictures of the ignition module. You have said that you have an electronic ignition - we need to verify that, and find the kill wire coming out of it.
Will get the numbers. It is not an old engine and by that I mean it does not have points. The kill wire attached to the magnetron unit via a spade connector.
Just confirming that if I take this wire to ground via a momentary switch, to create a kill switch that this will not hurt the magnetron.
Where the wire went to on the carby and there are two points have been butchered by the previous owner
It was manufactured on 13 October, 1988, so of course it has Magnetron ignition, as you said. The Magnetron has only two wires coming out of it: the thick high tension lead to the spark plug, and a longer, thin black wire with a spade connector on the end of it. This is the kill wire. Usually the kill wire is also connected to the Magnetron by a spade connector, but it may be hard-wired at that end. The kill wire normally runs to a contact on the governor plate above the carburetor. On most models, this contact touches the speed control lever on the governor plate when the speed control is set to minimum. This shorts the kill wire to ground, which stops the spark.
The kill wire works by grounding the internal part of the Magnetron that corresponds to the moving point in a points system. That makes the module function as if the points are not opening and closing, so there can be no spark. Hence, running the kill wire to either a momentary switch or a normal on/off switch, the other side of which is grounded, is a safe and effective way to stop the engine. I would not recommend the use of a momentary contact switch, since that would leave you with no way to disable the engine except disconnecting the spark plug. This creates a risk that at some time, someone will accidentally start the engine while working on or around it. However a toggle-type switch, that will remain in the ground position once set there, is suitable.
Remember, the kill wire must not be connected to a non-zero voltage. There have been many reports of Magnetrons being destroyed by ride-on mower tenants who connected the kill wire to the +12 Volt terminal on the starter switch, instead of the switchable ground terminal.
Last edited by grumpy; 14/01/1302:36 AM. Reason: Add detail
Hi Nev, Welcome here, I don't know anything regarding the kill switch on that model number but all the Briggs kill switches are a very basic design. What is this motor on so we can get a better idea of what it is
Hi Nev, I'm guessing, but from where the wire comes out through the crankcase it will be points/condenser ignition so the lack of spark can be any of those or the coil. Not sure but you may be able to fit an electronic coil from any of the thousands of Briggs rotary mower motors. If you can give me the coil mounting bolt centers and a measurement from center of one of the coil mounting bolts to the flywheel I can check to see if the later coils will fit, pretty sure it should, if so then you will have spark.
According to the IPL it has a Magnetron ignition. Also according the switch was on the control panel but it looks this one has been modify for an external kill switch.
Ok AVB, if it has a magnetron coil then all Nev needs to do is disconnect the wire wherever he can, then if he still has no spark then the coil is the problem.
Ok AVB, if it has a magnetron coil then all Nev needs to do is disconnect the wire wherever he can, then if he still has no spark then the coil is the problem.
Now is of course that is based on the model and type numbers given. If it is like it is here people swap these shrouds without even thinking about the important of the numbers. But I am fairly certain with the wire being a thin black wire it is the magneto kill wire.
Hi again - pulled recoil starter off - twin black wires from Magatron one comes out the front and one goes somewhere near carbie (haven't pulled) aircleaner off yet to check. Cleaned Flywheel (rust) and Magnatron and now have a good spark.
Sorry to bother you again would this be active ie stopping the motor starting? If so how can I disable. I have a good spark but motor won't fire. Depending on your response next step will be carbie over haul.
Now have you try injecting fuel directly via spark hole to see if it hits? It does then its carburetor problems; otherwise, there are several other things to check.
