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SS12 ignition issues

6796 Views 24 Replies 6 Participants Last post by  Dennis.Stroba
Yeah, the wife is going to have my head. I bought a 1968 SS12 this weekend.

I was going to weld a Suburban-style receiver on the front of my 10/6, but the mechanicals don't line up nicely. Buying the SS12 seems like the easier solution. Unfortunately, this gal doesn't run (yet.) I've replaced a bunch of suspect wiring from the previous owner. I've got good compression. The carb has been thoroughly cleaned out. I'm unable to get ignition with starting fluid.

If I pull the spark plug, I get a mediocre spark when cranking. I'm not convinced that I'm getting any spark when the plug is reinstalled. I used a spare plug held in-line with the installed plug to give me a visual indication, but I don't see a spark. I'm thinking that the compression load is preventing the coil from firing at the low cranking RPMs.

I've swept through all the ground return connections, and cleaned them thoroughly. It's possible that the timing is wrong - I'll grab my timing light tonight, but I'm unfamiliar with setting timing on this engine (HH120.) I haven't pulled the air shroud yet, so I can't say what kind of ignition system I have. Any suggestions on things to check before I rip out the ignition system and replace it with an automotive type?
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To test the ignition you unhook the kill wire. There should be a little screw with two wire's hooked to it, on the front, lower, engine shroud, flywheel side. One wire goes to the key switch, the other goes under the flywheel to the SSI. The one to the key switch is the kill wire. You can leave them both unhooked but not touching each other. If it starts you will have to choke it to trun it off.

By unhooking the kill wire you are elimitating the tractor wiring from the engine. If you don't have spark then the SSI is bad.
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I pulled the spark plug, and held it's base to the head while cranking. I get a spark, but it's pretty mediocre. I'm thinking that with the plug installed, the compression slows cranking and makes the spark even weaker. As I mentioned, I haven't yanked the cooling shroud yet, so I haven't seen the coil trigger setup. Maybe the gap is too big, or the trigger pickup is out of alignment.

There was some goofy wiring on this tractor when I got it. The main key switch had been replaced with one that can't handle the starter current, so the previous owner installed a solenoid. The battery and starter leads were connected to the solenoid with short pieces of 12AWG and teeny little crimp lugs. That's been rectified, but I'm expecting that there are other "modifications" lurking.

I also dug out my inductive timing light last night, so I should be able to check where the spark is being applied. The book says I need to remove the serial number plate to access the timing marks. I'll just yank the fan shroud (if it ever stops raining here ... sheesh.)
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Nice find!..looks like the clone of the '67 SS-12 I picked up with no engine last week!..If all else fails you could convert it to use a car ignition module..or perhaps borrow the engine off your other tractor to use on it..
If available time becomes an issue, I'm very inclined to rip the 10hp Briggs mill off the Beater 10/6 and drop it onto this frame. The perfectionist in me doesn't like the franken-tractor prospect (future maintenance becomes a major chore,) but I don't want to spend infinite resources trying to resurrect one machine.

Compression is good. The carb has been fully disassembled and looks to be in working order. From a basic operational perspective, all that's left is ignition (suck, squeeze, bang, blow.) I'm bypassing the fuel delivery system, and just using a spray of starting fluid. It doesn't even pop on that, which I find really unusual.

I scrounged a coil and resistor from my car-parts junk box (the "other" junk box ... no not that one, the other "other" one.) I may cobble something together just to see if I can get this thing running. I'd feel better if I can do just that. The timing light may provide some clues as well.
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Page 47 has a couple different set ups. You have one of them. My guess is the one on the left, at the bottom of page 47. This page tells you how to test things.

If power gets put to the frame in any way it can burn the SSI up. With the screwed up wiring and that battery hook up it's possible this has happened.

Sometimes a switch will go bad and put 12v to the kill wire. That is all it takes.

Page 46 is newer then yours, gear starter's.
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It was pouring down rain this morning, and is scheduled to continue doing so for the next three days. Ugh. It'll take a few days before I get a chance to yank the blower cover and look at the electronics.

Speaking of which, here's a shot of the "new and improved" starter solenoid (before I further improved it):

You can see the red 12AWG bridging wires that connect the 6AWG battery cables to the solenoid. It's clear that these were installed because the hole in the battery cables didn't fit on the solenoid studs directly. The starter spins noticeably faster with direct connections to the solenoid. I also like the original battery ground cable hovering dangerously close to the battery-side of the solenoid.
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I dont see how you'll get a car coil to work,without any points,you'll need to devise some way to "trigger" the coil..there are instructions online on pulling tractor sites how to add a auto pick up coil to the HH Tecumsehs ,but I find their method of winding one yourself out of magnet wire and a sewing machine bobbin,and an aluminum trigger wheel made from scratch, a bit too complicated for me,and I'm not a dummy when it comes to ignition systems..

It seems to me there would be an easier way to do it,like use a pick up coil a car uses and adapt that somehow to the flywheel or crank PTO to sense when to "fire" the coil..and use a GM 4 prong HEI ignition module instead of a Chrysler one....too bad you cant just bolt a magneto from a smaller Tecumseh under the flywheel,and use the points..WHY they decided "Solid State" was "better", I dont know..would have been,if they didnt stop making replacement coils and the related parts for it!..its about the only "bummer" the HH engines have,really..
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Robert this is the easy way. There is a few different set ups so it matter's which fix you use.

This is the starter/gen engine fix.

Corse we don't know he needs a fix yet.
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I got the fan shroud off this evening. Looks like I have the "SSI under" ignition. The coil matches the pulse transformer 610760 shown on the lower-left figure on page 47 of the 8to18 document. I checked the connection to the key switch. It's hard grounded when "off", and I see voltage pulses in "run" when I spin the flywheel. Clouds rolled in, so I haven't re-assembled such that I can spin at speed with the starter motor. I'll put the timing light on the coil output and spin the motor with the plug removed, then repeat the test with the plug installed.

I don't see any timing marks on the flywheel. Anyone know if the crank keyway is cut in-line with the connecting rod journal? (i.e. may I infer TDC by placing the keyway in a vertical orientation?)
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Yes the flywheel key is in-line with the connecting rod journal.

The only timimg problem I ever heard of with the set up is a sheared flywheel key.
Good info Small Fry,at least I know there is a "ready made" solution to any SSI woes I might encounter on the Suburban I have equipped with it..
(another way out would be to put a DIESEL in it!)...
I yanked the engine apart today. The previous owner thought there might be a burned exhaust valve, so I was thinking that I didn't have good compression, thus no "bang." Both valves look to be in great shape. They extend above the block enough for external inspection. I shoved a feeler gauge between the lifters and the valves, and there's plenty of clearance, so they're not being held open when they shouldn't be. I put the motor at TDC, and I noticed that the crank keyway is decidely not vertical.

So I'm thinking that I have a bent crank. That would suck. However, before bailing and just swapping out the mill, I went back to basics and brought the engine forward from first principles. I cleaned all the gunge out of the interior of the flywheel. I sanded the rust off the magneto armature and clear-coated the exposed metal. With the flywheel reinstalled, I marked TDC as well as 10- and 20-degrees BTDC (determined by measuring the flywheel circumference and dividing by 36.) Convenient marks were scratched into the flywheel and backplate. I scrounged through my wife's stuff and located some white nail polish to enhance the marks (honest, that's the *only* reason I rifle through her belongings.)

With the head removed and the starter belt put back on, I tie-wrapped a spare spark plug to the carb stud and I cranked away. I observed good spark, and the timing light showed a solid TDC strike before abruptly advancing to 20-degrees BTDC (apparently cranking without backpressure produced enough RPMs to fool the SSI unit into thinking it's running.) Okay, put the head back on and install a spark plug. I've still got good spark on the external plug, and the ignition is happening solidly at TDC. So I moved the spark wire to the proper plug, and confirmed that the timing light is still triggering ... yep, solid TDC still. So I grabbed the starting fluid, and whaddya know? She runs just fine.

I suspect the previous owner had done some work and reassembled it improperly. Possibly the replacement head gasket wasn't seated tight. There was grease and oil everywhere, and I suspect the coil wasn't grounded well. I changed a gazillion variables all at once, so I'll probably never know the actual cause. I'm just glad she runs - the wife was rather upset that I paid good money for a "dead" tractor.

Many thanks for the discussion. It was definitely helpful to have folks willing to kick around ideas and troubleshooting methods.
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I should have included a shot of the timing marks.

The circumference of the flywheel at the block is about 24.5 inches. 10 degrees is approximately 11/16 inch, so marks were made at 11/16 and 1 3/8 (i.e. 22/16) from the TDC mark.
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Glad you have it working. I have a SS12 crank out on the bench and the flywheel key looked to be vertical at TDC.

I'll have to look closer to see, it must be like yours I would think.
Glad you got her going!..

I'd bet it would be near impossible to bend or twist a crank ,the keyway HAS to be in the correct spot...
I have seen cranks BREAK,but not twist or bend,at least not on the flywheel side of an engine..

I hate it when you cant pin down WHAT was the cause of the problem,I run into that myself often--you find several things "wrong",and fix them all,then wonder WHICH "fix" actually "fixed" it!..
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nice find, off topic a bit but a weird space for the battery, but just as a thought, they have those (for you) harbour frieght motors (for me) princess auto. they are called jiondongs or something. Just my 0.02.
Good tip about measuring the circumference and dividing by 360!
I should pay more attenion to what I'm doing. I ran out to look at the crank when you asked about TDC. I was looking at the pully side not the flywheel side. :sorry1:

Pully side of the crank looks to have the key way TDC and the flywheel is like your photo.

Maybe this is so you can see TDC with out pulling the flyweel nut ?


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Right back at you. It never occurred to me that there would be *another* keyway on the other end of the crank (which makes perfect sense now that you've pointed it out.) The top-down photo of the nekkid crank definitely shows the relationships.
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