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Hi, I've got a Briggs & Stratton lawnmower which I'm repairing for a project. It's a 4 stroke, QUANTUMXM 3.5 HP (an L-Head). It was very dirty when I got it and was full of oil but I cleaned it out by hand and tried to drain the oil as best I could. I think the spark isn't working as I have tried to pull the flywheel with the spark plug removed but there is no visible spark, though you can feel a static electrical shock. I've been using several new spark plugs so it can't be that. Any ideas?
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I rarely find bad coils. Set the air gap, the gap between the coil and flywheel magnets to .010 of an inch and check for spark again.
The bet tool to check for spark is a .166 gap inlike spark tester. Most inline spark testers are set to this gap. If you have spark using the inline spark tester, then the coil is fine.
Another method to check the coil is too remove/dis-connect the small ground wire on the coil. The connector should be a spade type terminal. Dis-connecting the small wire isolates the coil and if you have spark then you know for sure the coil is fine. If there is no spark with the ground wire dis-connected then the coil is defective.
Let me know what you find.
Eric
I've tired what you said about disconnecting the ground wire and I changed the armature gap to .010 but there was still no spark. Does this mean as you said that I ahve to get a coil? I also don't think I can get a inline spark tester in the UK as one of the dealers said they haven't heard of it. I also spoke to a Briggs & Stratton dealer over the phone and he said that I had to put a mower blade on, otherwise it will give a sharp kick back but I'm not sure whether this is right. He also spoke about ignition points but I don't know what they look like and I'm not sure whether my engine has them as they aren't labelled in the illustarted parts list.
Regards Guy
Answer -
In-line spark testers should be easy to find...every auto parts store here in the US sell them for less than $10.00.
As for the blade, you should have one on the engine. The blade actually acts as part of the flywheel weight/rotating mass.
For the points, check the last 2 digits of the code number. If the first 2 digits are 81 or higher you should have electronic ignition.
You can use the spark plug to test the spark. The inline spark tester simulates spark during the compression test. I have only found one coil that would jump the spark plug but not the inline tester. If the only part connected to the coil is the spark plug wire and spark plug you should have spark when you touch the spark plug to the engine metal and pull the string. Pull the string as if you are starting the engine, above 350 RMP.
Let me know what you find on the code number. If you think you may have points, you should have 2 small wires connected the coil and one of the wires will run under the flywheel to the points and condenser.
Let me know what you find.
Eric
My code number is 92082458. I don't think I have points as there aren't any wires going under the flywheel and connecting to points and I only have one wire coming from the coil which I think is a ground wire, as you said.
I have tried touching the spark plug (while it was connected) to metal at the top of the engine and screwing it in, then pulling the wire but there is still no spark.
I'm also going to try and get a blade for the engine so it acts as part of the flywheel and I will also inquire further into an inline spark tester.
Answer -
You should definitely have electronic ignition. Like I said, I rarely find bad coils but it does happen.
Does the coil have any markings on it like "This Side Up"?
Let me know.
Eric
The coil does have several markings on it. It does have "This Side Out"-which faces up, and beneath the coil it has "Cyl Side"-which I think stands for cycle side. It also has the number "12" on the top left side of the coil. It also has a number, "9223P", and this faces the flywheel. I don't think, if it were a possibility, that the coil could be the wrong way round as the ground wire isn't long enough to reach the other side of the coil.
Regards Guy
AnswerSounds like you have the coil installed correctly. If you have no spark with the ground wire dis-connected then the coil is bad.
Do you have a friend with a similar engine? Most Briggs coils are about the same size; in fact I think there are only 3 different coils for the single cylinder L head series.
Anyhow, see if you can borrow/test your friends coil.
Let me know what you find.
Eric
