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Discussion Starter #1 (Edited)
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!
 

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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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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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Discussion Starter #6
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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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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Discussion Starter #8
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??:tango_face_plain:


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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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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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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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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Discussion Starter #12
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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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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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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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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Discussion Starter #17 (Edited)
OK, thank you 38Racine! you have confirmed everything I'm seeing, re the two green kill wires going into the sleeve and coming out as only one green wire, and that each has a diode more or less hidden by the sleeve!

At this point I have replaced the coil on the weak cylinder, thought I was home free - not so. Not sure I set the gap exactly right: used a standard flat feeler guage and combined the .0120 and the .004 to get the .0124, placed it in the center of the coil between it and the magnet. It does run, but the intermittent issue is still there and now there's an occasional backfire, which I attribute probably to me not getting the air gap measured just right and so affecting the timing on that cylinder - not sure - maybe I should have measured the air gap on the outside ends of the coil instead of the middle. ??

Intermittent still, even with the green leads disconnected from the coil and taped off.

So, I removed the front cover from the carbs, checked the fuel flow to that cylinder - seems to flow ok, no obstructions, no obstructions visible from the inlet fitting.

I removed the bowl cover - looked ok, and I put it back on.

Since it still runs intermittently even with the green leads off the coil I'm thinking it has to be an intake system problem. I'm especially suspicious of those electrical devices - I think you or someone called them "anti-backfire solenoids": I know nothing about these things so I don't know how to troubleshoot them, and apparently you have to totally remove the carb to get to it.

Was it you who mentioned removing them and replacing them with bolts: do you think that would help in this case? And, what do you do with those electrical leads?

One observation I've had is that even with the green wires disconnected from the coil, and while its running, turning off the key does in fact kill the engine! Is this because those electrical things are killing the fuel flow? If so, and if one of them is defective could it be causing that cylinder to fire intermittently?

I'm attaching a video so you can hear and see - the weak cylinder is on the r/h side in the video, (l/h side from the seat looking forward).
So, here's how it sounds. I'm thinking fuel flow. both kill wires are disconnected and taped off.
Maybe those electrical things on the carbs?
Note the surging as it runs at a high idle.

I don't think fuel pump as that would affect both cylinders.

OK - I can't seem to add the video since it's an MP4 taken on my Android Samsung Galaxy Note9 and it's too big even converted to a .zip - So I've copied in the file/link name below but I doubt that it will work for you.

20190713_162706_512163665688869.mp4

I have been able to email this file to myself, so I know it can be emailed. It's 17mb btw.

Thanks again for your time and advice, let me know how it's going with your machine!
 

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Yes. When you turn key off power to the carb solenoids with stop the fuel going into main jet and engine stops. I just taped the solenoid hot red leads and left hanging. You might try a 50-50 mix of seafoam in the tank. Run for short runs. May miss a bit and smoke. Let sit and then repeat a bunch of times. That might clean any small blockage in the carbs.
 

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If you don't mind the mess, you can remove the ABF solenoids, and check them with a 9V transistor radio battery. When power is applied, installed or not, you should hear the solenoid click as it withdraws the jet blocker. It should also click when power is removed as the spring pushes the pintle back into place to block the main jet feed. You should be able to feel/hear the click as you move the ignition switch from OFF to ON.
tom
 

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Might need to pull the carbs to remove the abs as they are on the engine side sideways into the carb bowl. Not below the bowl like briggs.
 
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