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Briggs 28M707 no spark


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04-20-13, 05:53 AM   #1  
Briggs 28M707 no spark

Hey guys I have a Briggs and Strattton 28M707 on my ride on mower. All was fine last time I used it and next time I went to start it, it refuses to fire up. It turns over and there is fuel going into carb. I took the HT lead off and I am not getting a spark. I disconnected what I think is the kill wire and still no spark. To give a little background the ignition switch does not work, I have to bypass the switch and have done for a long time, it is also kept outside under a tarp as I have no room to store it inside. Growing season is here and I have nearly an acre of grass to cut very soon and am desperate to get this running again.
I am suspecting it is something to do with an ignition module or coil or something similar?
There is a square aluminium box mounted on the engine with two wires coming out of it, it is filled with a clear/yellow epoxy. Would I be correct in assuming this is what give the spark?
It is on a Westwood T1300 ride on mower if that helps.
To let you know my skill level I am fairly capable with my hands as I am an electrical engineer to trade and have been repairing machinery all my life in factories. Everything from compressors to vacuum pumps to cnc machines to refrigeration and air-con.

Any help in getting this engine going would be very much appreciated

thanks in advance

 
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04-20-13, 06:15 AM   #2  
Hello dazdidge,

If you disconnected the kill wire from the coil and still have no spark the issue is the ignition module (coil), The coil is located under the flywheel cover. The module you described with two wires is the voltage regulator for the charging system.

Remove the top cover then disconnect the kill wire from the coil body and check for spark again, If still no spark replace the coil, If spark regains check the kill lead wire for shorts.

If you have to replace the coil adjust as below;


Rotate the flywheel magnet away from the coil. loosen the two mounting screws then pull the coil away from the flywheel and just snug the two screws.

Rotate the flywheel magnet in front of the coil and insert any business card between the coil and magnet (0.010-0.014). Loosen the two screws and let the magnet pull the coil to the flywheel, Hold a slight pressure on the coil pushing it against the flywheel then tighten the screws. Rotate the flywheel to remove the business card......

Good Luck

 
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04-20-13, 06:31 AM   #3  
Thanks for the reply, as you can tell I don't know much about small engines! But the regulator you mention sheds light on the battery not charging, I have to take the battery out after every use and recharge it as the cutting deck relies purely on the battery if I remember right. It kept failing to engage the magnetic clutch.
I went back outside just now and removed the kill wire from the coil and still no spark. I removed the coil and a few of the laminations are starting to split so I would imagine the coil is gone, I wish I had checked this sooner! To check for shorts on the kill wire am I just using a multimetre or ohm-meter to check between the wire and ground? Also, is there any way of testing the coil or is it just a case of replacing it?
I really need to keep this mower limping along for a wee while as we just had to replace the wife's car due to faulty control module. It was going to cost over 1000 pounds to repair as the job could only be done by the manufacturer and as it was over ten years old it wasn't economical to repair, we have already spent 1400 pounds on it in the last year! No pennies left in the bank :-(

Thanks again for your reply, most helpful. I found this place just the other day as I was having problems with a couple of small honda generators not putting out voltage, needles to say that thanks to this place they are both now working :-) Wish I had found it years ago

darren

 
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04-20-13, 07:09 AM   #4  
Hello Darren,

Yes, Check the kill wire with a multimeter as it shouldn't show a closed circuit to ground. Yes, Replace the coil....

As for the charging system, It may not be functioning due to your faulty ignition switch. One of these wires coming out of the regulator should travel behind the starter up under the flywheel, The other should travel to and connect to the tractor wire harness.

With use of your multimeter, Do you have battery voltage on this harness wire going to the regulator ?

 
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04-21-13, 01:12 AM   #5  
Checked the kill wire with a meter and it appears to be ok. Not had a chance to check the charging system yet but will hopefully get it done today if we get a break in the rain. Found ignition coils on ebay and they are pretty cheap, just need to make sure I order the correct one. Now to see if I can find the ignition switch as well.

thanks again for your help.

 
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04-21-13, 06:03 AM   #6  
Does anyone know what the measurements would be when testing the magneto with a multimeter?
Between the plug wire and the metal body I am just short of 5 k ohm
Between the plug wire and kill wire terminal I am just short of 5k ohm
Between the kill wire terminal and the metal body it is 0.5 ohm. I would assume the last reading is bad as it will direct the spark down to earth/negative and not let it go to the plug?

 
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04-21-13, 07:04 AM   #7  
Hello Darren,

Briggs doesn't list any test specs for their ignition modules, With the kill lead disconnected they either work or don't work. That's the only test I've used over 30 yrs, So I've never put a meter on a new one (waste of time)......

 
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04-21-13, 10:07 AM   #8  
Also, be careful of the coils on ebay. Make sure you buy an original coil made by briggs. Aftermarket coils do not last long... sometimes days, sometimes hours, sometimes minutes. Original coils last years, usually decades.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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