Tecumseh 5hp - No Spark

[AdmiralYoda]

1980's Troy-Bilt Horse Rear-Tine Rotor Tiller with the Tecumseh HH50 5hp engine. Two years ago it ran fine. Went to use it last year and halfway through tilling it started running like crap. Didn't want to take throttle and just ran poor. This year I couldn't even get it started with starting fluid! Verified no-spark.

The carb was a rusty mess so I'm putting a new one on there. But I'm a little stumped on the no-spark situation. The kill-switch wire seems grounded all the time, even if I unplug it from the throttle kill switch.

Any obvious things to check on these old engines? I'm planning on taking the front cover off and see how the points contacts look. Anything else to check while I'm in there? Thanks!

 

[martinq]

1980's Troy-Bilt Horse Rear-Tine Rotor Tiller with the Tecumseh HH50 5hp engine. Two years ago it ran fine. Went to use it last year and halfway through tilling it started running like crap. Didn't want to take throttle and just ran poor. This year I couldn't even get it started with starting fluid! Verified no-spark.

The carb was a rusty mess so I'm putting a new one on there. But I'm a little stumped on the no-spark situation. The kill-switch wire seems grounded all the time, even if I unplug it from the throttle kill switch.

Any obvious things to check on these old engines? I'm planning on taking the front cover off and see how the points contacts look. Anything else to check while I'm in there? Thanks!

Do you know if it uses solid-state ignition coil / module or points & condenser? I think it's solid state, if not I would definitely change it out for a modern coil.

I would swap the coil and check your valve gaps.

 

[CleanSump]

Did you follow the kill wire all the way to the source to see if the insulation has worn through and grounding it along the way?

 

[AdmiralYoda]

@martinq Not sure yet on the coil. It is old, early 80's or possibly 70's. I'll be taking off the front cover to look tonight.

@CleanSump Haven't looked yet, front cover comes off tonight and I'll dig in more. I ran out of time last night but I unplugged the kill wire from the throttle stop and put my multi-meter on it. Was a bit hard to do one-handed but when I spun the engine by hand the grounded wire may have opened once per revolution.

 

[mk378]

The kill wire is attached to the coil primary, so it always is going to have a low DC resistance to ground. If it is a points system the resistance will decrease further while the points are closed. That can be tested by turning the engine slowly. The points should open just as the magnet passes the coil. Once you have the cover off, you can tell if it has points by looking for a wire teeing off the kill wire and going under the flywheel.

Oil on the points is a common cause of no spark. The oil causes a high resistance when closed.

 

[Propflux01]

A bit confused here. You say it has no spark, but also that it has a rusty carb and won’t take throttle. Sounds to me like it’s the carb/ fuel tank with the issue, not a no spark condition

 

[AdmiralYoda]

A bit confused here. You say it has no spark, but also that it has a rusty carb and won’t take throttle. Sounds to me like it’s the carb/ fuel tank with the issue, not a no spark condition

Two separate issues. Last year it began running rough, not taking throttle well and just ran poorly. This year I removed the fuel bowl to take a look and it was nasty so I got a replacement carb. I put the new carb on last night and went to start it then nothing, wouldn't even fire with starting fluid.

I took the spark plug out and it looked fine and turned the engine over with the spark plug grounded and didn't see any spark. That's about as far as I got last night other than unplugging the kill wire from the throttle stop and trying again. Still no spark.

 

[jeepman3071]

A Tecumseh in the 70s/80s may or may not still have points, they were experimenting with electronic ignition around that time so some of them had it. Definitely check any kill switches/wires. I had a Tecumseh snow king with no spark and mice had chewed the kill wire to the coil which caused the wire to ground out on the shroud. A new wire fixed it.

 

[AdmiralYoda]

Good news....it runs! Traced the kill wire back to the coil and it was fine.

This model tiller has a factory battery and electric start option. Someone had installed a homemade off-on-start key switch for the electric start at some point.

No matter what position the switch turned to...it was electrically in the off position.

The battery has been dead for years so I just used the pull start. I bypassed the key switch and what do you know....it runs!

I'll need to get a new throttle spring as this one is on its last legs and can barely get off idle. Easy. Back in service, thanks guys!

 

[Propflux01]

Cool. Thanx for the update.