No Spark

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  #1  
Old 08-01-03, 09:17 PM
KeeperOfTheGood
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No Spark

Hey oh

I have a project engine. It is no longer in production, and the original manufacturer is all but forgotten. I realize and accept that I may need to have parts custom made by the time I am finished (eg. Head Gasket).

It is a Suffolk Iron Foundry (1920) LTD, engine type 75 G 14 Model 1B. It is most likley from the 'Punch' mower that was sold circa 1954-7.

There are several hurdles to getting this UK fellow running, and the first is the absence of spark. (next will be getting the mud from the mud dauber wasps out of the carb.)

I have tested the coil and it is, I believe, good (50k/5k), I have tested the capacitor and it is good (discharges to arround 60k, and builds to about 90k), the points are clean enough to be new, with at leat a 32nd or more of contact surface on them, and they are set to .020, and don't have an oil film on them. All the wires have continuity, and none are shorted or open. The magnet in the flywheel still lifts a spanner.

So, what am I missing? Its been over a decade since I took highschool small engine repair, but I can't believe I have fogotten it that badly.

Any ideas would be appreciated
 
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  #2  
Old 08-02-03, 03:01 AM
mower17's Avatar
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Location: southern louisiana
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I have already had a similar problem with a 30 year old briggs. I e-mailed briggs and they said to test the coil for resistance. They said it should have between 2500 and 5000 ohms. I checked it and it was within spec so I went 3 months thinking it was still good and that I must have missed something. Well, eventually I got an old used coil that still worked and come to find out, the coil on the mower was bad afterall. So your coil might be defective even though it tests out good.
 
  #3  
Old 08-02-03, 09:42 AM
KeeperOfTheGood
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Hey oh

Thank you for the reply mower17. It is feasible that the internal insulation has lost its hi-pot capability. Hence my 1.5v VOM would not show this failure mode, unless the insulation were actually carbonized.

The coil that is in this engine is an open bobbin type. As much as I could wind this coil by hand myself (something I have done some years back) I would rather not. I have found a few places on the web that are offering this service. I live in Canada, would it be easier for me to locate a Canadian company, or is it just as expedient to use one in the US? Baring in mind that most places want the whole assembly and one even the flywheel, and some return the re-built unit with proprietary parts!

For me the bigger criterion would be that it be as visually true to the original as can be.

Ad(Thnx)vance!
 
  #4  
Old 08-02-03, 09:19 PM
cheese's Avatar
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Hello KeeperOfTheGood!

It is still possible that the coil could be shorting under a higher current load, but I would go over everything several times before I went with that theory. Check the systems' timing, watch the magnet pass the magneto, and the relationship of the points and piston to determine whether it is close, or obviously mis-timed. Make sure the kill circuit is not shorting somewhere (I imagine you have already checked this). Make sure the capacitor case is grounded well, use an ohmmeter to be sure. Make sure the insulator for the points contact is good, and check with an ohmmeter to be sure they are not grounded. Sometimes grounds and insulators give trouble on these older engines. I think some used leather and wood for insulators and they may have deteriorated enough for current to find a way through them.

I would like to hear how this goes! Keep us up on the project, and we'll help any way we can.

BTW: I like your "thanks in advance" (ad(thnx)vance). Never saw that one before.
 
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