Merc 500- No spark on #3 cylinder

S

squamlake

Cadet
Joined
Aug 5, 2002
Messages
6
I've got a Merc 500, 1977, Serial #4578711. Not getting any spark on #3 cylinder. Could the switch box be bad? I swapped out the coils on #2 and #3 but the same cylinder still has no spark. This tells me that the coils are fine. If it is the switch box, how much money are these things?
 
S

squamlake

Cadet
Joined
Aug 5, 2002
Messages
6
Re: Merc 500- No spark on #3 cylinder

Trigger wires being the wires that come from the switch box to the coils? Someone also told me that the contacts underneath the fly wheel may also be causing this problem. Something to do with these contacts under the fly wheel telling the engine when to fire.
 
12Footer

12Footer

Fleet Admiral
Joined
Mar 25, 2001
Messages
8,217
Re: Merc 500- No spark on #3 cylinder

The trigger is a ring with 2 coils of wire in it.<br />It is located under the flywheel,so check it with an ohm meter 1K scale, you should get between 40 and 900 ohms (depending on the engine model, and I can't look it up now.<br />But at any rate, it should have resistance less than 1000ohms on iether,and on both coils....Disconnected at the switchbox,of course.<br />BTW, if you find a scource for this trigger for less than 78buks,letme know, ok? I got one in the front yard,and the grass underneath it is dead.
 
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