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Hi all!

I'm helping a friend that was given an old Simplicity snow thrower with a Tecumseh engine that we have no info about.

I did the usual primary checks: spark, fuel directly into cylinder and got it to cough off. I then dunked the carb in the ultra sonic cleaner and we tried to start the thing. When spraying fuel directly into the carb it runs with good power but as soon as I stop feeding it it dies. I found an old carb that is the same with a little smaller throttle throat diameter and tested...same behavior, it starts and runs as long as I squirt fuel directly into the carb and dies as soon as I stop. I tried to cup the carb to force fuel to be drawn from the float bowl (which gets filled) but nothing.

I'm totally at a loss here. We know it has spark, we know that there is compression and obviously it has air. The only thing missing is the fuel...but why doesn't it draw it from the bowl with either of the two carbs? I have tried to see if there is any intake leaks but I can't see anything that indicates any cracks or bad gaskets. Also, when I cupped the carb there was pretty good suction.

We have ordered a new carb (Chinese from Amazon for about $10) but to me that's a shot in the dark since we tested two different carbs and there was no difference.

Any one with any idea what can be the issue?

Kind regards
Fred

Model spec and serial no of engine so we can look at what you have. Throwing a carb in an ultrasonic cleaner doesn't necessarly clean all the passages in the carb. Sometimes you have to run something through the orfices to clean them out. Honda has a good set of orfice cleaner but pricey.

What I know is that it is a Tecumseh hm80. Don't think I have seen any information plate.

I did use compressed air through all the passages and even some carb cleaner through the pick up pipe (don't know the name of it...is it emulsion tube maybe?) and it looked to be good flow thorough it.

Also, since the behavior is identical with two different carbs it seems unlikely that they would have the same restriction of fuel...but hey, you never know. The new carb will be delivered in a few days so then we will get the answer if it's carb related or something else. The latter is why I started this thread. What other reason can this engine behavior be if it's not carb related? I've been racking my brain but I can't really think of anything else.

Fuel pump or gravity feed?
take the line off at the carburetor and see if you have fuel present there.

Gravity feed. There is good flow in the fuel line before the carb and the bowl does fill up. It has the needle screw in the middle of the nut that fastens the bowl to the carb so I have been checking that there is in fact fuel in the bowl.

Two things to check. First the needle is the high speed fuel mixture screw. Intial adjustment from lightly seared is 1 1/2 turns out. Second on the side of the carb you will see a small plastic cap. Under this cap you will find the idle mixture jet. Remove this jet and make sure that both orifaces, horizontal and vertical, are open. They like to plug causing your problem. Here is a service manual which may help you out. https://www.mymowerparts.com/pdf/Te...P-4-CYCLE-L-HEAD-FLAT-HEAD-ENGINES-692509.pdf

Rivets said:

First the needle is the high speed fuel mixture screw.

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REALLY?!! That would explain EVERYTHING!

Now that you told me this it's 100% logical. Why would a drain screw have a needle? *face palm*

This is the first carb I have messed with with that kind of bowl screw so I just assumed that the knurled screw was for draining the bowl. It's a snow blower and I know that they run a higher risk of getting water in the tank and float bowl. The needle part did confuse me but I didn't think of that the main jet always being in the bottom of the bowl.

Wow...I feel a little stupid now. I'll have to check with my friend to see if he has ordered the new carb...

Thank you so much Rivets! I'll report back when I get the machine running...which probably will be next time I can get my hands on it.

Ps And thank you for the service manual! Ds

Rivets had the correct diagnosis! I turned the screw 1 1/2 turns out and my friend pulled the cord...the machine started on the first try. I did some tweaking of the high and low screws and the engine ran really good!

Unfortunately either the drive for the auger or the wheels worked as they should, and I think that spare parts for this machine is almost impossible to get here in Sweden.

This machine shows heavy signs of having been ran hard and put away wet so I really don't think it worth the time and money to fix it...but I'll let my friend decide. He got it for free and in my opinion he should sell it for a few bucks and buy another one. It's way to big for his yard anyway.

Thank you all for your help! I will never mistake the main jet adjustment screw for a drain screw again.

Before scrapping out this unit please make one more check. Auger and wheels not preforming properly are normally caused by one of three things. Bad belts, bad tensioner pulleys, or bad tensioner arm. With these old mules I would be trying to repair before buying 90% of the new pieces of crap on the market today.

Rivets said:

Before scrapping out this unit please make one more check. Auger and wheels not preforming properly are normally caused by one of three things. Bad belts, bad tensioner pulleys, or bad tensioner arm. With these old mules I would be trying to repair before buying 90% of the new pieces of crap on the market today.

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I hear you and I agree. But my initial fault finding is that the auger woodruff keys are gone. I can rotate the impeller without the input shaft spinning, and I haven't found a source for keys here in Sweden.

And, as I wrote, I think there are a bunch of things that need attention so I feel that this might be a can of worms waiting to be opened. If it was mine, and I had the space for it, I would definitely give it a go...but since my friend is not that technically inclined I feel that it might be a little too much for him to tackle. The machine is mechanically worn out with everything sloppy and some parts missing, so I think that it would be best to sell it as a parts machine or for someone else to restore.

Ok, I wish I was there to take it off your hands.

Rivets said:

Ok, I wish I was there to take it off your hands.

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I can check the shipping costs over the Atlantic!

Id stay away from anything simplicity. They are owned buy Briggs and stratton and from what i heard they are either selling the line or eliminating it. they are doin the same with snapper too.

Nick, first I wish you would read and understand the entire thread before making a comment like that. We’re talking about an old Simplicity blower, old mule was my name for it. Second, I’ll agree Briggs purchased Simplicity but even the new Simplicity units are better than most of the crap built today. I’m not saying they have the same past quality. Finally, can you name one of today’s snowblowers that was built with the same quality of a 10 year old Smplicity?

Yeah...and this machine was built when Simplicity was a part of Allis Chalmers which means it from 1983 or earlier. Back in the days when stuff was made to last...but it's over 40 years old so it's no wonder it's worn.

Paxman said:

Yeah...and this machine was built when Simplicity was a part of Allis Chalmers which means it from 1983 or earlier. Back in the days when stuff was made to last...but it's over 40 years old so it's no wonder it's worn.

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I have a 1976 Ariens snowblower that is built like a tank.

You can make a woodruff key yourself with some patience. Maybe take a little time and go through the snowblower and see what it needs. Maybe it is too worn out, but typically snowblowers have very little hours on them.

Tiger Small Engine said:

I have a 1976 Ariens snowblower that is built like a tank.

You can make a woodruff key yourself with some patience. Maybe take a little time and go through the snowblower and see what it needs. Maybe it is too worn out, but typically snowblowers have very little hours on them.

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I want to thank all of you again for your suggestions, but due to circumstances this machine will not be fixed by me or my friend. It's just not worth the effort and money for us. Maybe some one else have the time, money, energy and space to get it running again.

Read your post & thought you may reconsider purchasing carburetor overhaul kit for original carburetor.

Paxman said:

Hi all!

I'm helping a friend that was given an old Simplicity snow thrower with a Tecumseh engine that we have no info about.

I did the usual primary checks: spark, fuel directly into cylinder and got it to cough off. I then dunked the carb in the ultra sonic cleaner and we tried to start the thing. When spraying fuel directly into the carb it runs with good power but as soon as I stop feeding it it dies. I found an old carb that is the same with a little smaller throttle throat diameter and tested...same behavior, it starts and runs as long as I squirt fuel directly into the carb and dies as soon as I stop. I tried to cup the carb to force fuel to be drawn from the float bowl (which gets filled) but nothing.

I'm totally at a loss here. We know it has spark, we know that there is compression and obviously it has air. The only thing missing is the fuel...but why doesn't it draw it from the bowl with either of the two carbs? I have tried to see if there is any intake leaks but I can't see anything that indicates any cracks or bad gaskets. Also, when I cupped the carb there was pretty good suction.

We have ordered a new carb (Chinese from Amazon for about $10) but to me that's a shot in the dark since we tested two different carbs and there was no difference.

Any one with any idea what can be the issue?

Kind regards
Fred

Click to expand...

Replace the gas line. blow tank out from drain or gas line.

Tiger Small Engine said:

You can make a woodruff key yourself with some patience. Maybe take a little time and go through the snowblower and see what it needs. Maybe it is too worn out, but typically snowblowers have very little hours on them.

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Plan A: If you don't feel like shaping a new key, hardware stores often have a good selection of woodruff (and straight) keys. Measure slot length and depth at center, plus measure width to select the new key.

Plan B: Metric & SAE woodruff keys are on line at places like Grainger, McMaster Carr, Zoro (Grainger's lower priced child) & Drill Spot (Grainger's higher priced child).

Plan C: (Fast Repair - Not Sanctioned) Drill through the shaft and piece. Insert a shear pin or weak bolt with a cotter pin retainer instead of the woodruff key. Shear pins are at most hardware stores and all lawn equipment/small engine stores.

Mine's like that because the shaft's slot was bent & mushroomed when the auger hit a chunk of ice. The shaft metal is softer than the key's. It was an outdoors, (-) 17-C day in January temporary fix that I never went back & fixed correctly.

If you absolutely decide that you don't want the machine, I'm sure it will be easy to sell whole "as-is" or parted out on Bonanza or eBay. In the listing, you can make it so the buyer arranges for a shipping company to pick it up so you don't have to mess it.

Snälla njut idag!
Paul

There’s a lot of great information here, thanks, Alan

Paxman said:

Gravity feed. There is good flow in the fuel line before the carb and the bowl does fill up. It has the needle screw in the middle of the nut that fastens the bowl to the carb so I have been checking that there is in fact fuel in the bowl.

Click to expand...

Here is something I recently learned from experience working/restoring a vintage 2002 sam's club troybilt "gardenway" riding mower with the B&S 16.5 HP single banger OHV engine. Here was the first things I noticed and replaced/repaired

1. the fuel tank was absolutely filthy and blocked.
2. All the line, and filter was collapsed and blocked, including the shut off valve
3. I cleaned the carb PROPERLY and replaced all the seals and o rings. I even bought a cheap 18 dollar after market nikki carb so I would have extra spare parts and another carb to troubleshoot with.

I still have a rough idling engine, that was far too high in rpm and the choke made no difference. From this I reasoned the engine was running lean...not enough fuel OR a air leaks somewhere after the carb to the engine. I checked all the gaskets after the carb.

I then did a leak down test...that passed...the compression test also passed...(old iron sleeved cylinders still holding great pressure.) Out of abundance and just preventative, I did a complete head cylinder recondition, valve lapping and cleanup and piston cleanup and then proper torque and sequence with a new OEM gasket and then a proper valve clearance/lash.

engine still was idling too high. and choke still made no difference. swapped with the extra carb...no change.

then I removed the exhaust muffler...slight improvement. there was a massive wasp nest inside the muffler blocking it...cleaned that up and reinstalled. stills running hot and idle too high, but at least the exhaust isn't cherry red, just red hot. Not good.

then finally, after all these things, I decide to take the fuel shut off and the fuel filter OUT of the line and run it straight. Voila'...normal operating fuel mixture.

this is a gravity fed fuel system. There is no vacuum or pump to provide fuel pressure. The fuel filter was one of those 150 micron large clear filters. WRONG! the proper and correct filter is a 40 micron red disk filter..this allows proper fuel flow in a gravity fuel system...the wrong fuel filter was causing fuel starvation and running lean. the fuel shutoff was slightly restricted internally due to some weird sort of fuel related "melting" of the plastic materials. It would not fully open when in the fully opened position. So that got replaced also.

engine purrs like a kitten.

also noting: I inspected the flywheel woodruff and keyway to make sure timing key was not borked and I unloaded the drive belts just to make sure there was no hangups. I also checked to make sure the decomp valve was operating normally and that the governor was operating normally. I mentioned these things because it was necessary to go over EVERYTHING. And yes, I changed the oil and the plugs. I set the gap every so slightly just a bit more than oem spec. After 10-20 hours, I plan to reset this back to oem spec. (in older engines that have set for long periods, my thinking it is better to have a rich condition to do another breakin period. and yes, I added a little bit of marvel mystery, but really any 2 cycle engine oil in the fuel will accomplish the same.

I write these things down, not to shotgun a do to list, but to provide an overall idea of what I did to restore and old machine. Finding the root cause of a frustrating lean and rough idling conditions is more or less detective work. You will find the problem if you continue to look for it and test for it. And don't overlook the most simple things, like I did. it was the wrong kind of fuel filter and blockage/damage/defect in the fuel shutoff valve.

the other things I would have done anyway...because that is just preventative maintenance. This engine should last another 20 plus years if I do all the TLC things to maintain it. The body and chassis and deck...well that's a different story. a project to repair rust damage and do some welding and replace spindles, tires, bearings and both sets of transaxle seals and snap rings. A winter project for raining days. Add this one to the other 19 I have in the lineup. To be repaired and resold as restored. good times.