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Trying to dignose an OHV v-twin. Bench tested the coils with an old analog ohmmeter, but not certain how much resistance indicates a good coil.

Unless you are using a $ 45,000 signal generating testing machine your results are wothless.
The coils have an embedded trigger chip and can not be tested with an OHM meter.
Even worse if it is one that sends a heavy signal down to measure the voltage loss in order to determine the resistance, that signal can fry the new chips.
Some publish figures for the secondary resistance but as you can not test the primary , testing the secondary gets you no where.

IF you suspect a coil problem, I suggest you disconnect the "Kill Wire" from the base of *both* coils and try the engine. There are more problems with this kill wire harness than with the coils which are very reliable.

Walt Conner

Tinkerer200 said:

IF you suspect a coil problem, I suggest you disconnect the "Kill Wire" from the base of *both* coils and try the engine. There are more problems with this kill wire harness than with the coils which are very reliable.

Walt Conner

Click to expand...

Thank you! It fired right up. I was concerned that I wouldn't be able to turn it off, but after a few seconds it shut off by itself. Maybe that seat shut off kicked in.
As far as replacing the part, I'm not seeing a part number for it on the Murray electrical diagram, nor on the B&S diagram available from Jack's Small Engines.

You are not likely to find any help here without a model and type number for the engine. However, you local B&S Dealer will know what you need taking the old part in.

Walt Conner

All of the safety switches that shut down your engine are connected to that kill wire.
So what ever shut down the engine was not related to the safety switches.
Get some sort of spark tester , hook it up and try again.
If the sparks stop before the engine stops then that coil is faulty.
A lot of them will work fine when cold then crap out when they get hot.
Test them first, as Walt says most that get replaced are quite fine .
Do that and get back to us

Tinkerer200 said:

You are not likely to find any help here without a model and type number for the engine. However, you local B&S Dealer will know what you need taking the old part in.

Walt Conner

Click to expand...

bertsmobile1 said:

All of the safety switches that shut down your engine are connected to that kill wire.
So what ever shut down the engine was not related to the safety switches.
Get some sort of spark tester , hook it up and try again.
If the sparks stop before the engine stops then that coil is faulty.
A lot of them will work fine when cold then crap out when they get hot.
Test them first, as Walt says most that get replaced are quite fine .
Do that and get back to us

Click to expand...

Tinkerer200 said:

IF you suspect a coil problem, I suggest you disconnect the "Kill Wire" from the base of *both* coils and try the engine. There are more problems with this kill wire harness than with the coils which are very reliable.

Walt Conner

Click to expand...

Mower and engine model numbers have been added to my profile on the left.

I performed the spark test as bert suggested using a tester with a large visible gap. During the test, both kill wires to the coils were disconnected, the other plug wire was connected to the plug. A spark jumped the gap during both tests and engine ran until shortly after I removed my foot from clutch/brake pedal. Spark was visible on both until engine shut down. (I don't yet understand what killed the engine, but that's a lesson for another day.) Correct me if I'm wrong, but I believe that I can conclude that the coils are fine. (I'm wondering if I should also do the spark test with the coil wire attached in different combinations.)

My next step is to look for shorts in the kill wires and re-test the safety switches with an ohmmeter. My test method involves removing the switch and simply attaching the probes to each terminal on the switch and noting whether a resistance is present when it's supposed to be. This is one of the first things I did when trying to start the mower and all switches were passed, but I"ll do it again because I don't know what else to do.

It's good to hear the engine running.

Yep , coils are fine
it wont hurt to try again with the kill wires attached.
the wire between the two coils has a diode in it to prevent them interfearing with each other and sparking out of time .
If the engine dies when you move the pedal, check the wire to the fuel solenoid, it could be grouning out on the pedal or one of the multitude of stuff attached to it and stopping the fuel to the main jet.

bertsmobile1 said:

Yep , coils are fine
it wont hurt to try again with the kill wires attached.
the wire between the two coils has a diode in it to prevent them interfearing with each other and sparking out of time .
If the engine dies when you move the pedal, check the wire to the fuel solenoid, it could be grouning out on the pedal or one of the multitude of stuff attached to it and stopping the fuel to the main jet.

Click to expand...

In checking the kill wires for shorts I found a couple of places where it, and the gray wire, had been smashed behind the starter exposing some of the bare wire. I taped them up, connected the kill wires, engaged the safety switches and tried it again, but it would not fire.
The gray fuel solenoid wire looks good other than what I described above. Is it time to replace that front harness.

Having sound wiring will not hurt.
Having a few scotches before you order the loom also helps.
I finally got some terminal tools so I can make my own looms while retaining all of the original plugs.
The prices are silly.
The wires from the plug near the starter motor are Briggs engine parts and from there on it is a Murray part.
With the wires to the coils disconnected then only electrical thing that can kill the engine is the solenoid which is spring loaded off and held open by the grey wire.
The solenoid should also have ground wire as well and these give problems.

bertsmobile1 said:

Having sound wiring will not hurt.
Having a few scotches before you order the loom also helps.
I finally got some terminal tools so I can make my own looms while retaining all of the original plugs.
The prices are silly.
The wires from the plug near the starter motor are Briggs engine parts and from there on it is a Murray part.
With the wires to the coils disconnected then only electrical thing that can kill the engine is the solenoid which is spring loaded off and held open by the grey wire.
The solenoid should also have ground wire as well and these give problems.

Click to expand...

Yeah, I'm going to hold off on ordering a new harness for a bit.
I took the mower for a short ride. After shutting it down I noticed that the kill wires and gray fuel solenoid wire are routed directly on top of the cooling fins making it very easy for the insulation to melt off. Where can I get a diagram showing how these wire should be routed around the starter and to the coils, and to the fuel solenoid. There was little slack in them to route them elsewhere.

Never seen one.
A lot of the lower covers have a loom clip to hold the solenoid wire and I usually cable tie to the dip stick tube.
there is a bit of a grove behind the starter where the wires usually run.
Nothing in the shop at the moment with your motor in it.

I think the JD technical manuals have some wire routing photos but they are the only ones I can remember.