hard starting??worn impulse coupler?

My hard staring 0-320 problem might be solved. Guessing here and would like any help. Reading back on some of the past posted ideas some one suggested the impulse coupler. I had thought that the impulse coupler would be good because when I pull the engine through by hand I could here the coupler snap. So I thought it would not be the problem, but... When I first attempt to start my engine it has a fast rotation, (hot battery) but does not fire up. After the battery gets low and after I have messed with the starting for 30 minutes letting the starter cool down between starts and by then the ENGINE WILL STILL TURN... BUT VERY SLOWLY that's when the engine starts. Just like you have turned on the ignition. I think that the impulse coupler is worn and when the engine is cranking fast the couple can not engage so it can't wind up and produce the spark I need. I will know for sure when my mechanic pulls the mags (slicks) Anyone been through this? thanks teeweed

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teeweed, I agree with TJ. I think we must be the only two guys on this site that are supporters of the old Bendix magnetos. I have to agree there are advantages to the Bendix mags, #one in my opinion is they tend to have a stronger spark, and the best reason I see is they are very easy to overhaul, with parts readily available.
Good luck with your hard starting engine, and it sounds like you'll have it fixed directly...
Champdriver

I like Bendix, run them till the engine TBO's with no problems especially after they dropped the impulse coupling AD on the four cylinders.

Mark, How much time is on your Slicks?

Hard starting

I've seen this problem numerous times with Slick mags - If you pull the mag off and spin the mag quickly the pawl on the impulse hits the pin and makes a snapping sound but doesn't "catch" on the pin to wind the impulse. If you spin it slowly they'll catch almost every time. Just pulled a 700 hour Slick mag last week for the same problem - found the impulse assembly rusted and gummed up.
I've seen Slicks worn out with 1000 hours on them and several of them on 0-360 Lyc. that sheered the main shaft internally.
I'll stick with Bendix - We have one set of Bendix that have ran 20+ years, thousands of hours and several engines. I take them apart about every 1000 hours, repack the bearings, replace the seal and change any other worn parts as needed - seems to work well.

Champdriver said:

.....there are advantages to the Bendix mags, #one in my opinion is they tend to have a stronger spark.......Champdriver

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I agree, I've run plugs with my old Bendix mags til the electrodes were eroded way down & the engine still ran fine. Seems like about 500 hours is all plugs are good for with the new Slicks I put on about 7 years ago, even though the electrodes still look good they don't want to fire properly. I'm convinced that the smaller coil in the Slick throws less of a spark than the big Bendix. However, I do like Slicks for their compact size & clean looks and the flexibility in mounting due to using clamps instead of bolting through ears on the mag case.

Eric

Steve I have logged 291 hours on them. Looks like they have a TOTAL of 965. They were installed with a re-manufactured engine in 1997. They still look shiny and nice. I hope they look that way on the inside. I might as well get ready to ORDER a new impulse coupler..... ..unless for some reason it's just gummed up and can be cleaned. Also hooking up the primer system at this time. Hope to get it done, the Brazos river is starting to show some good landing spots. ... teeweed

Have the e-gap been adjusted in the past 965 hrs? If not I would do that while you are at it. I haven't found any problems with Slick impulse couplings. Found several messed up Bendix ones because the people complying with the 500 hr. AD screwed them up. Probably why they recended it on the 4 cylinder engines.

I don't think the mags have ever been off. I thought it was odd at the last annual that one of the mags was off 10 degrees. teeweed

Check and set the e-gap. As the points wear the internal timing of the magneto changes which really effects starting. Seen it many, many times. If your mechanic doesn't know how or doesn't have the tools send me the mags and I will do it. I'll bet it fixes your problem.

Steve I will do that if I can't get the problem solved here. Other than a buzz box and feeler gages, are there any other tools to set the e-gap and point gap? The more I have studied about magnetos the more this 40 plus year old technology impresses me. Thanks teeweed

There is a special tool that is used to hold everything in the right position. It is inexpensive and I have the instructions I could post.

I would like to see it. Thanks teeweed

Pulled the mags and it turns out that the impulse coupler was not catching and doing it's job while cranking. As suggested the mechanic will also check the e-gap and point gap. Thanks for all the help. I think I have had a weak impulse coupler for over a year...shame on me! teeweed