Greetings Lawn World,
I have an old Craftsman lawn mower with Briggs and Stratton 5.5 engine (Model # 128802-1519-23, yes, very old). I was having problems starting so upon examination, found that the primer bulb was cracked. I replaced that and while I was at it, changed the oil and spark plug. It started and ran great for one time only. The next time I could not start it. I have fuel and air so I fell upon the spark as an issue. I tested the ignition coil as per directions on YouTube (With the kill switch connected and unconnected) and found no spark. I bought a new induction coil but still no spark. I should say there is a very weak to non-existent spark, if I hold the plug in my hand I get a very weak jolt sometimes. I set the air gap on the coil with a business card that measured .010" with a caliper and also bumped it down to .006" with a feeler gauge. No luck.
I am grasping at straws to find a solution as there seem to be no other electrical components evident.
Could I really have Two bad induction coils?
Do I need to insulate the coil on the bottom where it mounts to the engine?
Attachments
#2
davbell22602
Have you checked the flywheel key? How much compression does it have? Is the engine stop cable stretched? Air gap is .010 on a Briggs coil.
davbell22602,
I have not checked the fly wheel key as the fly wheel turns easily with the spark plug out and the piston moves and the valves open and close as I turn the crank. The stop cable does not seem to be stretched, it pushes rather than pulls, the brake is completely off the fly. When I get a chance I will check the compression. It's an old engine so,,,
As stated before I'm grasping for an answer but it seems that logically, either there is little spark generated or the spark is running straight to ground. Induction is induction, I should be able to pass a strong magnet over the coil and generate a spark via magnetic flux. I'm wondering, I've been turning the fly by hand, if I could turn it faster would this make a difference in the strength of the spark, i.e. a sharper spike so to speak? Or am I thinking too much? The air gap is set to .010". Thanks for the reply.
Could you have install the coil upside down, the kill terminal should be down close to the block? It has happened. Also, do not insulate the coil, the two mounting bolts provide you ground. I doubt you have shear a flywheel key, as you would still get a hot spark, but at the wrong time.
Rivets,
No, the coil is right side up. If you look closely at the picture you can read "This side out" or something and the kill connect is on the bottom. Although it would be easy to install it upside down. My tools will stick to the magnito but I wonder, do they lose their magnetic strength over time? Seems unlikely.
#6
EngineMan
Can you re gap to .015" and see if you get spark.
#7
reynoldston
you keep saying its a old mower just how old? if that is so it will have ignition points and condenser. They would be under the flywheel and if so either clean and re gap the points or replace them.
you keep saying its a old mower just how old? if that is so it will have ignition points and condenser. They would be under the flywheel and if so either clean and re gap the points or replace them.
But its fun to watch people dance around after somebody cranks the engine, and they have good spark.
Years ago owned a wisconsin 7 hp engine with the old style magneto ignition. You could turn the flywheel by hand and it would click when it energized the mag and sparked. My brother wrapped the starter rope around the starter pulley, and had me crank the engine slowly. It got him three times before he could let go.
Greetings Lawn World,
I do refer to mower as being "old", it is 20 years old and to me seems old for a mower but what do I know, jus' sayin'. I bumped the air gap to .015" but no luck. There have been some comments about testing for spark correctly, could I have been doing it incorrectly? I have the plug connected and I ground it on a freshly cleaned (1000 grit emery) part of the engine and trun the fly, with the kill wire connected and disconnected. I held it in my hand just as a last resort and felt a mild, very mild, jolt from time to time, not consistant-and not a good way to test-You'll only make that mistake once. As for points and condenser, I looked under the fly wheel and see nothing, also there were no such parts listed in the exploded diagrams I've seen. I haven't taken the fly wheel off though. I've had a lot of cars in the past with points etc. but the ignition system on this thing seems dead simple, if there were points and a condenser they would have to be in line somewhere. I'm leaning toward the original idea that B&S may have sent me a defective part. There have been some good ideas here and I am greatful for the help.
#12
Fish
No, these ignitions are pretty much straightforward. If you spin the flywheel with a coil bolted on, and get no spark, and the kill
wire disconnected, then the coil is bad. Well the flywheel may have lost it's magnetism, but I have never seen it.
So if you have correctly checked the spark, as stated above, then the coil/coils are bad.
Fish and Rivets,
Thanks I was getting a little worried there. The part number I have from Briggs and Strattons confirmation email is: 590454 -ARMATURE-MAGNETO. Which, obviously does not match the one posted by Rivets. I don't remember the part number from when I ordered it but I used the B&S web site and the model and type number (see first post) that was stamped on the metal cowling of the mower to order the part. It sure looks like my original coil, which is why I thought I had a good match. The original has a factory stamp 9508P which was useless in searching. I'm going to have to search part #802574 and see what turns out. Thanks folks, could be on to something...
PS. Like the Gonzo icon by the way, I'm a big HST fan.
Hello again,
Lord, how did I screw that up? I have my notes from from my search of the B&S web site and they gave me the choice of #793353 or #590454...this is why I don't like ordering on line.
Anyhow, I'm getting part# 802574 and I'll post back when it arrives. Thanks for all the help with this puzzel.
