Home › Forum › Ask A Member › 15 Evinrude 1975 no Spark Driver coil ?
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fleetwin.
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May 31, 2015 at 3:15 pm #1646
I’m working on a 15 hp 1975 Evinrude it started out 1 cyl spark only now none. I’ve checked points gap cleaned, all grounds cleaned tried different external coil no fire . CDI doesn’t go that far back to find out DVA or testing . I suspect Driver coil (charge coil ) but want to make sure . I tested the brass ring in mag plate to make sure no movement very snug so ruled that out . Anybody familiar with this system ??
May 31, 2015 at 4:30 pm #17283The majority of no spark conditions are due to breaker points not making good contact, or improperly adjusted. I know you said you checked them, but are you sure?
May 31, 2015 at 5:54 pm #17289Yes, I even removed them cleaned mag plate cleaned points several times carb cleaner ,Emory paper ,electric cleaner ,paper bag , set with your tool and ohm meter both sets . So I know its important to this type ignition so I think w can rule that out .
May 31, 2015 at 6:43 pm #17293Did you check the resistance of the driver coil and be sure it is NOT shorted go ground? Typical resistance is several hundred ohms. A bad driver coil would surely kill both cylinders, but the driver coils are a fairly rugged part only damaged by being rubbed by the flywheel or perhaps chafed leads. True, the driver coils have been updated/improved over the years, but I’m thinking the driver coil is NOT causing your no spark condition unless the resistance is way off or it is physically damaged. As all have stated, both sets of points have to be in good shape, one bad set could kill spark to both cylinders. Be sure to disconnect the stop switch to rule that out. The harness in the mag plate has been known to get pinched, cracked, or split causing problems. Be SURE the mag plate is properly grounded, it has an actually ground strap lead from the mag plate to the block. Check the resistance between the mag plate and a good block ground using the low ohms scale, any readings over a few tenths of an ohm is NG.
CORRECTION: Driver coil resistance is only a few ohms, not several hundred! Different models and years of production resistances vary a bit. I know there was a service bulletin years ago advising a different resistance spec for newer/updated driver coils, but don’t have access to that bulletin.
May 31, 2015 at 7:22 pm #17295I did clean ground on block and mag plate .I can run those tests as u indicated I took d-coil off cleaned the ground mag plate under and coil bar. Other than physically looking and checking timing mark opening closing I cant see them as bad not pitted etc. My Merctronics says condensers are good and external coils testing good . but will get back to u . I wonder is there any test on the driver coil to see if its within spec. etc. ?? Thanks for input
May 31, 2015 at 7:26 pm #17296To check the driver coils resistance in your low tension magneto, undo the leads at the points and hook them up to an ohmmeter set at it’s lowest ohm scale. The resistance should be 1.45 +/- 0.4 ohms.
May 31, 2015 at 9:59 pm #17312quote Mumbles:To check the driver coils resistance in your low tension magneto, undo the leads at the points and hook them up to an ohmmeter set at it’s lowest ohm scale. The resistance should be 1.45 +/- 0.4 ohms.Sorry for the wrong info, the driver coil resistance is indeed only a few ohms, not several hundred ohms like I advised earlier.
May 31, 2015 at 10:09 pm #17313quote cannuck:I did clean ground on block and mag plate .I can run those tests as u indicated I took d-coil off cleaned the ground mag plate under and coil bar. Other than physically looking and checking timing mark opening closing I cant see them as bad not pitted etc. My Merctronics says condensers are good and external coils testing good . but will get back to u . I wonder is there any test on the driver coil to see if its within spec. etc. ?? Thanks for inputCheck that ground strap connection with an ohm meter, don’t just clean the connection. Be sure to rotate the mag plate while resistance testing as well. You can check those mag plate primary leads/harness with the low ohms scale as well, again be sure to rotate the mag plate while testing to help show split/intermittent connections. Check for shorts to ground/mag plate using the high ohms scale, readings less than infinity indicate the lead is pinched/shorted to the mag plate somewhere. Are you using the coil locating tool to ensure correct driver coil air gap?
June 1, 2015 at 4:41 am #17330I did not check air gap do not have a tool for that. Anyway to go about this without it . I did check resistance on both blue wires from coil it reads 2.56 higher than 1.4 ohms don’t know if this will create the no spark
June 1, 2015 at 8:45 am #17335Driver coil’s laminated core ends should be flush with the machined edges of the posts it sits on. Tool is not a necessity, just a convenience. If it is set too close, it will drag on the magnets, too far away, will cause weak or no spark depending on how much too far.
I hesitate to comment on the resistance reading. Not enough experience with keeping up with the possible changes.
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