Major help needed.. Mercruiser 140 hp 1986

B

biggjimm

Chief Petty Officer
Joined
Jul 15, 2015
Messages
403
Check the coil like flipbro said. You may have to get a hold of the tech dept at flamethrower though as I found out different coils have different specs. I had a coil that tested "bad" as per the generally accepted guidelines however, upon contacting the manufacturer, it was actually just fine. Jim.
 
Motodox

Motodox

Seaman Apprentice
Joined
Sep 7, 2015
Messages
42
Thank you everyone for the advice and direction on tracking this problem. I have like 7.9 v at the coil with the key on. I have around 3.2 ohms between the post on the coil. I will check resistance on the coil wire after work.

Maybe I should call flame thrower and double check what they call for.

What's weird is I can have my volt meter out one end in the + post on coil and ground to the engine I have 12v. I can also have the black wire off the - post of coil which runs to the ignition module under cap and get 12v but soon as I bring that wire and my test lead to the - post of coil it drops back down to like 8v ... Is this because the coil is sucking up the power? Is that ignition module actually grounded cause I don't understand why I'm getting a good ground from the black wire coming out , idk maybe that right. Is that where the coil gets its ground? I have two wires coming from - post on coil one great which gots to shift interrupt and one black that goes to ignition control module.

I want to pull my hair out !!

How big of a gap should that spark jump to tell if it's sufficient, I have a spark plug tester with a adjustable gap
 
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biggjimm

Chief Petty Officer
Joined
Jul 15, 2015
Messages
403
The module grounds the coil - terminal which causes it to spark. When testing the resistance of the coil, remove all the wires from it. I think there's something in the stickies that tells you which setting to have your ohm meter set to. I don't recall but it's a different setting for each test. You want to check both the primary & secondary sides. Pos coil term to neg coil term & then move the black lead from the neg term to the center & measure resistance from the pos term to the center tower.

Temporarily unhook the wires going to your shift interrupt & the tachometer, only have the wires going to the distributor on the coil - & the wires from the ignition switch to the coil + & see what it does. Try jumpering directly from the battery + to the coil + & see what it does with full voltage to the coil +.

I think it should jump at least a 3/8" gap. I can't remember & I'm not home to look at my tester.
 
Motodox

Motodox

Seaman Apprentice
Joined
Sep 7, 2015
Messages
42
biggjimm said:
The module grounds the coil - terminal which causes it to spark. When testing the resistance of the coil, remove all the wires from it. I think there's something in the stickies that tells you which setting to have your ohm meter set to. I don't recall but it's a different setting for each test. You want to check both the primary & secondary sides. Pos coil term to neg coil term & then move the black lead from the neg term to the center & measure resistance from the pos term to the center tower.

Temporarily unhook the wires going to your shift interrupt & the tachometer, only have the wires going to the distributor on the coil - & the wires from the ignition switch to the coil + & see what it does. Try jumpering directly from the battery + to the coil + & see what it does with full voltage to the coil +.

I think it should jump at least a 3/8" gap. I can't remember & I'm not home to look at my tester.
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Ok thanks man, really appreciate all this. I'm going to try all this when I get off work today. I'll be back with what happens.

I know I have tried connecting battery jumper straight to + on coil and didn't get much.

All I know is this is driving me crazy, I wish I could find out if my module was bad or the coil. I'll be back with more details after work
 
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