Tecumseh 22hp One cylinder intermittently - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information
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post #1 of 34 Old 06-30-2019, 02:32 PM Thread Starter
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Help Tecumseh 22hp One cylinder cuts out/in intermittently

This is my first post, very glad to be here!

I have a 22hp Stanley tractor which is actually made by Murray and has a Tecumseh engine.

It has worked great til I ran it completely out of gas. So I refilled the tank (93Octane) and resumed. Soon, if not imediately, it began cutting one cylinder out, intermittently.

Out/In/Out/In/Out/In, you get it.

Thought maybe fuel filter, replaced that with new, no change.
Thought maybe spark plugs, replaced both with new, no change.

Disassembled fuel pump to check for damage or debris -looked ok.
Replaced two of the fuel supply lines, and the vacuum line that apparently powers the fuel pump (never seen that kind of arrangement). no change.

Gas is clean, no water, etc.

When running it sounds like a switch is opening and closing turning one cylinder off, and then back on, over and over.

And, when it's running on both cylinders, it sounds perfect, no backfires, no mechanical noises, it just sounds normal.

I've read on a different post that there are two coils that share a common kill wire involving a diode, and that this may be contributing to intermittent operation. If so, would it be that one coil is bad (suddenly, just when I happen to run dry on gas???), or, would it be that the diode is the problem?? I have yet to uncover the coils/diode as I'm hesitant to believe that's the issue.

Would greatly appreciate any guidance on this! It has otherwise been a very dependable engine and I am hoping this is a simple matter.

Many thanks for your consideration!

Last edited by mikeshoop; 06-30-2019 at 04:27 PM. Reason: Better Title
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post #2 of 34 Old 06-30-2019, 04:03 PM
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Re: Tecumseh 22hp One cylinder intermittently

Are you sure its a Tecumseh? Ive seen Kawasaki’s with diodes in the harness but not any Tecumseh’s. Either way I would check the coil gaps first.
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post #3 of 34 Old 06-30-2019, 04:29 PM Thread Starter
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Re: Tecumseh 22hp One cylinder intermittently

Yes, no doubt, I think the model is TVT691, definitely Tecumseh, approx 2006 model.
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post #4 of 34 Old 06-30-2019, 04:31 PM Thread Starter
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Re: Tecumseh 22hp One cylinder intermittently

Tecumseh engine model is TVT691 600803A, displacement 691cc, 2 cyinder V-twin.
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post #5 of 34 Old 06-30-2019, 06:13 PM
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Re: Tecumseh 22hp One cylinder intermittently

I got a free zt from my neighbour burnt in fire with that engine. I'm rebuilding it. Carb bowls were burnt off but I had some others. Had issue as it would only run on 1 cylinder. I have temp gauge to check exhaust temps. I found if I switched carb positions then dead cylinder switched. Eventually I got bowl kit for bad carb and solved. In process I replaced the AntiBackfireSolenoids on both with just bolts as I thought maybe one of them was failing. That might be your issue. The connection wires are in behind.
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post #6 of 34 Old 07-01-2019, 08:36 PM Thread Starter
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Re: Tecumseh 22hp One cylinder intermittently

Many thanks for your reply and your expertise - (never heard of an anti-backfire solenoid btw). I'm open to replacing the carb bowl.

Note that somehow this started right after running it out of gas - do you think that could have affected the carbs or the bowls??

And, did you just literally screw in bolts in place of the anti-backfire solenoids? Runs ok without them??

I'll be looking into identifying the cold cylinder and doing what you suggested, reversing the carbs and see if the problem follows the bad carb.

Again, many thanks for your response, I'm really unfamiliar with this engine.
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post #7 of 34 Old 07-02-2019, 09:31 AM
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Re: Tecumseh 22hp One cylinder intermittently

I just used bolts that were same diameter and thread pitch as the solenoid and cut to exact thread amount as solenoid. I also had a similar tec carb that just had bolt. I just let it idle a bit before shut down and no backfire.
Best price I got on bowl kit was repairclinic.com. look up part number using your carb number as there may be two . your carb will have 4 digit manufacturing number that can be crossed to 6 digit model number.
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post #8 of 34 Old 07-07-2019, 04:24 PM Thread Starter
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Re: Tecumseh 22hp One cylinder intermittently

Thanks, I really do appreciate the input and I really need to get this engine back to running right.

If I understand correctly, the anti-backfire solenoids are those things on each carb with electrical connections, red and green; and I'm assuming I could just remove those, replace with bolts with same thread, but then do what with the wires? just tape them off??


Also, I've ordered a replacement diode assembly just in case that's the problem but I can't tell where in the engine area its located, unless it's positioned below the intake system out of site? Any ideas on where this thing is located??

thanks again, Mike Shoop
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post #9 of 34 Old 07-07-2019, 08:15 PM
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Re: Tecumseh 22hp One cylinder intermittently

Looks like I'm in the boat with you. Mine seemed to be running ok so i got the deck belt and it was running and cutting but engine went south and was missing. I found exhaust temp higher on right side so swapped a carb top to original one. Now I got backfire on left side. I can see flame inside left carb intake. Since i was rebuilding a burnt engine i used coils and kill off a donor engine . I'll see if i have pics of wiring i used.
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post #10 of 34 Old 07-07-2019, 08:29 PM
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Re: Tecumseh 22hp One cylinder intermittently

It started giving problems immediately after running dry, sounds to me like debris in the carburetor. To check the ignition system put an inline spark tester on the lead and watch it as the engine falters.
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post #11 of 34 Old 07-10-2019, 12:40 AM
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Re: Tecumseh 22hp One cylinder intermittently

Run it at medium speed and pull one plug wire at a time( use a glove and towel or it will shock you.) It should run on both. Pull both plugs and hold to block and crank to check spark to see if it is nice and strong on both sides and consistent pattern.
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post #12 of 34 Old 07-10-2019, 07:51 PM Thread Starter
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Re: Tecumseh 22hp One cylinder intermittently

Did that. Spark looks weak on driver side (front left viewed from the seat) cylinder. That is with both kill wires disconnected from the coils. I have ordered a replacement coil ($36). Will update this post once it arrives and I test that. Many thanks for all your help!!
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post #13 of 34 Old 07-11-2019, 10:35 PM
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Re: Tecumseh 22hp One cylinder intermittently

Quote:
Originally Posted by mikeshoop View Post
Did that. Spark looks weak on driver side (front left viewed from the seat) cylinder. That is with both kill wires disconnected from the coils. I have ordered a replacement coil ($36). Will update this post once it arrives and I test that. Many thanks for all your help!!
where are you getting the coil? My unit has coils from a engine that had been running fine until the guy seized it from poor oil maintenance.
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post #14 of 34 Old 07-12-2019, 08:37 PM
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Re: Tecumseh 22hp One cylinder intermittently

I was just working on mine again. Left cylinder as I face the heads is definitely messed up. It was ok when I fixed carb on right side. Had hi on temp gauge on exhaust before my test cut run. I removed the kill wires from the coils and it was still bad. I added my own wires for testing. I could kill left side and right ran fine. Adding back left it ran bad and killing right only the engine stopped. I swapped the coils side to side but nothing changed. I did locate the diode in kill. The right wire comes across into a heat sleeve. The left one also goes into that heat sleeve. I found the diode just inside the top of the sleeve for the right lead. Since only one lead comes out the other end of the sleeve I assume they are spliced in the sleeve. I will have to pull sleeve off to see diode in the left lead. For now I have the left carb including the bowl in the ultrasonic cleaner.
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post #15 of 34 Old 07-12-2019, 11:02 PM
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Re: Tecumseh 22hp One cylinder intermittently

Quote:
Originally Posted by 38racing View Post
I was just working on mine again. Left cylinder as I face the heads is definitely messed up. It was ok when I fixed carb on right side. Had hi on temp gauge on exhaust before my test cut run. I removed the kill wires from the coils and it was still bad. I added my own wires for testing. I could kill left side and right ran fine. Adding back left it ran bad and killing right only the engine stopped. I swapped the coils side to side but nothing changed. I did locate the diode in kill. The right wire comes across into a heat sleeve. The left one also goes into that heat sleeve. I found the diode just inside the top of the sleeve for the right lead. Since only one lead comes out the other end of the sleeve I assume they are spliced in the sleeve. I will have to pull sleeve off to see diode in the left lead. For now I have the left carb including the bowl in the ultrasonic cleaner.
Update
Found the diode on second wire so each had diode before they join together. If new coil doesn't solve your problem you could make separate coil kill leads that don't join together. Run with them both ungrounded. That would eliminate the diodes as source of misfire. If it turns out to be a diode you could keep separate leads and run to a dpdt switch that would keep them isolated but allow you to ground both at the same time.
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