# What makes an engine stall under load?



## Dave C

Craftsman 22" with Tecumseh 12 cu in engine, series 1 carb.

My brother and I both have identical Craftsman snow blowers with the same problem. They start and run but when engaged to throw snow they die.

Mine is about 15 yrs old with a new carburetor (eBay), adjustable main, and idle jets. I've owned it since new and it's only been the last few years that it has given me trouble. His is newer with the non-adjustable carb.

We've been through the cleaning procedures and both carbs are spotless. We're at the end of the rope here, with major snow headed this way.

What is the likely culprit?

TIA


----------



## UNDERTAKER

some one will be along here to answer that question. I never run or mess around with those engines. so anyways ALOHA from the unfrozen TUNDRA.


----------



## CarlB

Older L-head Tecumseh engines have a bad habit of the exhaust valve recessing in the valve seat and losing valve lash. When the engine gets up to operating temperature the valve lengthens just enough to hold the exhaust valve open causing a loss of power. This among many other things could be an issue. 

Make sure the gas tank is vented, you have a good spark, and you already said the fuel system is working correctly. Make sure you have good fuel delivery to the carb.


----------



## classiccat

are you able to test compression?


----------



## GustoGuy

Yes. Exhaust valves tend to get out of adjustment as well as the carburetor s are really finicky. To fix Exhaust remove head and using a wire brush remove carbon from valves. Pull the door to the valve spring area and using a valve keeper removal tool pull valve keeper clip and the pull valve out. To fix you usually grind off a small amount of stem until clearance is correct when measured from the cam lob tappet to the valve stem. Also you need to lap the valve too to make sure it is seated correctly. If valve is damaged replace valve and grind to right length and lap to cylinder.


----------



## RoyP

Or maybe your machines are just running lean.....try running it with the choke on just a bit.....if this helps.....open your main needle valve just a bit, very small bits at a time. 

His is newer with the non adjustable carb, more likely to gum up....may need to be cleaned by soaking in carb cleaner. 
Good luck


----------



## Big Ed

Something else to check.
Mine was sucking in air through the plastic fitting the goes into the carb. Did they same thing, as soon as I went into the snow it died. 
Funny thing was that the fitting didn't leak gas until I finally wiggled it around, then I saw the crack.
Do you have the plastic fitting on yours?

Check the condition of the fuel line itself too.
Bad venting on the cap as mentioned.


----------



## Big Ed

When you say this, "They start and run but when engaged to throw snow they die."

Does it die, just when you engage the auger?
Or when you engage the auger and go into the snow, then it dies?


----------



## Coby7

dave c said:


> What is the likely culprit?
> 
> Tia


the load!!!


----------



## HJames

Coby7 said:


> the load!!!


I'm fairly certain the OP is looking for a culprit within the spectrum of his snowblower. 

Try pulling the plug and checking to see what the fuel mixture is doing in the chamber.


----------



## suspicionofignorance2

I follow what BigEd is getting at, and is what I was wondering...Does it run OK auger engaged without any snow ?? Assume that's what you meant by load...? Otherwise it could be a faulty safety switch, and it is shutting off the ignition..


----------



## Dave C

Thanks for the replies, guys.



classiccat said:


> are you able to test compression?


I have a compression tester, and the machine has electric start, so yes I could. Never seen a spec for that though. Any idea what it should read?



Big Ed said:


> Something else to check.
> Mine was sucking in air through the plastic fitting the goes into the carb. Did they same thing, as soon as I went into the snow it died.
> Funny thing was that the fitting didn't leak gas until I finally wiggled it around, then I saw the crack.
> Do you have the plastic fitting on yours?
> 
> Check the condition of the fuel line itself too.
> Bad venting on the cap as mentioned.


Yes, they all have plastic fuel inlet fittings. No drips though. I'll double check the gas cap vent.

Fuel line has been replaced. I installed a shutoff valve this year in the fuel line, and I've double checked that fuel flows through it OK. Spark plug is new.



Big Ed said:


> When you say this, "They start and run but when engaged to throw snow they die."
> 
> Does it die, just when you engage the auger?
> Or when you engage the auger and go into the snow, then it dies?


By stalls under load I mean when I push the machine into some snow. I can drive the thing around and engage the auger but as soon as it gets into even a couple inches of snow it wants to stall.


----------



## Ariens1976

To me it sounds like governor not kicking in?


----------



## threeputtpar

It sounds like your auger belt is slipping. Are they both the originals from 15 years ago?

I'll guess that when you pull the auger handle, the auger and impeller spin like they are supposed to but when you drive into the snow it will throw the snow okay at first and slowly throw the snow shorter and shorter until it just stops coming out of the chute and the engine stalls? While this is going on, you never hear the governor kick in and up the rpms? Classic belt slipping symptoms.


----------



## Dave C

threeputtpar said:


> It sounds like your auger belt is slipping. Are they both the originals from 15 years ago?
> 
> I'll guess that when you pull the auger handle, the auger and impeller spin like they are supposed to but when you drive into the snow it will throw the snow okay at first and slowly throw the snow shorter and shorter until it just stops coming out of the chute and the engine stalls? While this is going on, you never hear the governor kick in and up the rpms? Classic belt slipping symptoms.


A couple of things about what you've said ring true. The auger belt has been replaced recently, and the replacement was fairly easy to install. Maybe it's too long? Unfortunately I can't see the auger while operating the machine.

But why would the engine die instead of the governor kicking up the speed?


----------



## classiccat

Dave C said:


> A couple of things about what you've said ring true. The auger belt has been replaced recently, and the replacement was fairly easy to install. Maybe it's too long? Unfortunately I can't see the auger while operating the machine.
> 
> But why would the engine die instead of the governor kicking up the speed?


Another thing to check are the RPMs that you're running. do you have access to a tachometer?


----------



## suspicionofignorance2

If the engine dies under work load, then the belt is fine...Sounds like a gov that's not functioning..


----------



## RoyP

Yup.....check the governor linkage.....something has come undone


----------



## classiccat

you won't know if the governor is failing unless you're looking at the throttle plate while it's stalling.

If the engine is @/near WOT and the RPMS are still dropping like a rock, the governor/linkage is doing it's job...it's trying to deliver more fuel as the spool retracts.

What are the RPMs before the load is applied?...if they're too-low (3600RPM is max) then adjust to give your machine a fighting chance.

As mentioned earlier, you want to check compression. Gustoguy and CarlB mentioned the valve issue...bad valve seats and/or valve lash lead to low compression. There's not really a spec that I'm aware of mainly due to the compression release mechanism....as well as variation in testing. I'd say questionable compression when pull starting is anything below 50 psi...below 40 I'd say you definitely have a problem. On my HM80, with a new head gasket and valves lapped, I'm getting 135psi on the starter cold. My H35 that I also put a new head gasket and lapped the valves, I'm pulling around 80psi cold. Others recommend leak-down testing...I've never done this on an l-head.

Anyways, you're getting a lot of good suggestions thrown your way. One more is to find the L-head service manual and browse the troubleshooting guide. I'll see if I can find the link on here for ya! Good luck!

EDIT: Link for the service manual.


----------



## GustoGuy

It sounds Iike it could be a carburetor problem. Try adding a small amount of choke to the engine and if that prevents stalling the clean then clean the main jet and emulsion tube. You may want to try an aftermarket replacement carburetor too to see if that fixes the problem. Then again it could be due to exhaust valve not closing fully and this can really reduce power.


----------



## Dave C

Thanks again for the input fellas. Really glad I found this forum. I did a few tests yesterday and I have a bit more info to share -

Gas cap looks fine. I ran the machine with the cap on loosely and it made no difference.

Compression comes up to 45 PSI with the electric start. I also have a leak down tester and I think I'll give that a shot too.

Here's the scenario when using the machine -

Prime and start the motor using electric start (yanking the recoil is futile). Engine runs for about 10 seconds and dies. Wait half a minute and repeat. After 2-3 attempts it'll eventually stay running. Both machines behave exactly the same way.

To me, this sounds like the carb is running dry. I tried pushing the primer bulb as it was stalling and it didn't matter. Adding choke doesn't help either. Gas will spew if I push the bowl drain.

Once it's warmed up it stays running. Governor is definitely working - I can tap the lever and RPM will increase. I have the high speed set to specs (contactless tachometers are wonderful). Engage the auger and attempt to clear snow - if I advance really slowly the machine throws snow. But any more than a crawl pace and the motor just bogs down and stalls.

I'm thinkin' that the old girl has just reached end of life. For me it's no big deal since I've acquired a new blower, but my brother's machine behaves exactly the same way and he wants to put a Harbor Freight engine on it... that'd be a different thread.

Thanks for the insights.


----------



## classiccat

I bet it will run like a new machine if you address the low compression…it would be a nice project that can be done in an afternoon as long as it isn’t the rings and/or cylinder bore. You do need to purchase a few things in advance…I added price estimates.

Personally I would start by pulling the head & valve-cover (breather) off of the engine. It’s actually quite easy.


Clean of the carbon (_seafoam & a nylon brush works really well_)
Get feeler gauges to check the clearance between the bottom of the valve & the lifter.If clearance is below spec (_usually around 0.008_”), then you file/sand-away the end of the valve as CarlB/Gustoguy described; I use emery cloth & some cutting oil.
Remove the valve springs (_trickiest part of the operation without a valve spring compressor…I started by using 2 screwdrivers or an open-end wrench_) & pull the valves…then lap them (lapping compound is < 5 bucks and the suction cup tool is ~ 7 bucks)…there are videos up on youtube how to do this…very simple.Just be careful where that compound goes…try to keep it contained to the valve seat and away from the valve guide & cylinder!Clean-up really well with solvent/rags.
Buy a new metal head gasket (8 bucks) and spray it down with permatex copper gasket spray (< 5 bucks).
Bolt down the new head and torque to 200in-lbs (in ~ 60in-lb increments) in the correct order (service manual has this info)
Install the valves/springs & breather…probably need 2 new breather gaskets (7 bucks). I lube the valve stems (_where they go into the guides_) with moly lube.
Re-check your compression...hopefully you're smiling by now J
I re-torque the head bolts after a few heating/cooling cycles.Recently on my HM80, the torque dropped by 30inlbs after a few cycles.
 
If you go this route, there are a lot of good guys on here to help. If you go the predator route, a lot of guys have successfully done this repower as well. Good luck!


----------



## threeputtpar

Has the fuel line on either machine ever been replaced? Maybe a coincidence, but it sounds like they are both partially collapsed or blocked. Get the good stuff from an OPE shop if you do replace them. Also, run the line without the shut off valve and/or filter to get maximum flow and if that makes any difference replace them both, too.


----------



## Dave C

Fuel lines have been replaced, fuel flows OK.

Where's the best place to source head gaskets and such?


----------



## classiccat

Dave C said:


> Fuel lines have been replaced, fuel flows OK.
> 
> Where's the best place to source head gaskets and such?


I'm lucky enough to have an awesome small engine supply shop nearby (Newburgh Power Equipment). They're right off of I-84 Exit 5A if you're in the area. If you don't have anything local, gaskets can found at numerous places online (partstree, ebay, amazon, etc.). I'll usually get the part numbers off of partstree before stopping by...even better if you can bring in the old part.

The valve lapping tool/compound as well as the Cu gasket sealer can be purchased at your local autoparts store (autozone, advanced, etc.). You'll want a lapping tool with the small suction cup for your Tecumseh; the wooden-dowel version is plenty.


----------



## Dave C

Unfortunately the Tecumseh dealers in my area have disappeared. Searspartsdirect is showing the head and breather gaskets in stock, and I've dealt with them before. PartsTree has them too but I have no experience with them.

I've been down this road before on other motors, and I have lapping compounds and a suction cup tool. Never had much luck doing that though, for whatever reason I dunno.

From the exploded views it looks like just the carb, muffler and gas tank gotta come off to access the valve cover. I think I'll grab a wrench and see where it leads me.

Thanks again.


----------



## classiccat

Dave C said:


> Unfortunately the Tecumseh dealers in my area have disappeared. Searspartsdirect is showing the head and breather gaskets in stock, and I've dealt with them before. PartsTree has them too but I have no experience with them.
> 
> I've been down this road before on other motors, and I have lapping compounds and a suction cup tool. Never had much luck doing that though, for whatever reason I dunno.
> 
> From the exploded views it looks like just the carb, muffler and gas tank gotta come off to access the valve cover. I think I'll grab a wrench and see where it leads me.
> 
> Thanks again.


 Correct, it needs to be taken down to the block. Don't forget to take pictures of the linkages. 

I did a little surgery on my HM80 in my Toro thread if you want to see lapping...more important I believe in your case, is checking the valve clearance. This machine was an old-dog when I got it....now it's pulling me around the block!


----------



## GustoGuy

> I'm thinkin' that the old girl has just reached end of life. For me it's no big deal since I've acquired a new blower, but my brother's machine behaves exactly the same way and he wants to put a Harbor Freight engine on it... that'd be a different thread.
> 
> Thanks for the insights.


 Yeah. I would not dump too much money into that old Flathead engine either. 

Harbor Frieght Predator 212cc OHV engines can be bought for $99.00 with the coupon. They are excellent runners and have lots of torque and are very comparable to an 8hp flat head engine in power. I own 3 of them. Two of them are on snowblowers and one is on a minibike. Both you and your Brother most likely have a 5hp Tecumseh on the 22 inch wide Craftsman. Since it is a Craftsman it is most likely a 2 shaft engine with the chassis by MTD and they are not too bad to flip the transmission on and convert to a single shaft engine. Here is my thread on how to do it. Good luck and let us know if you have any questions if you should decide to do an engine swap. I bought this friction disk it works awesome for the swap
Mark
http://www.snowblowerforum.com/foru...chine-5-22-harbor-freight-predator-212cc.html


----------



## suspicionofignorance2

If you want to keep time and $$ at minimum -- check clearance of exhaust valve --if zero, remove and file the stem to gain clearance---have even heard of the filing being done in place [clean away all filings]---cement the valve cover back on...re-use the head gasket...Recheck the compression...Now 90psi or more..??? Run the eng...verify problem solved for now...Do a valve job latter--to do it right..


----------



## Dave C

I have gaskets and a proper spring compressor on order. Will report back when I get the motor opened up.


----------



## Dave C

*Update*

I found a parts source locally and replaced the exhaust valve on my 2/22 machine. Lapped it in best I could, trimmed the stem for .006 clearance which is in the middle of the 4-8 spec. Compression came up to 90 PSI and the machine runs and throws snow. Thanks muchly for the help and guidance on SBF.

Now I'm reminded again of why I hate this blower - the impeller chute clogs so easily with any kind of wet snow. But it runs again.

My brother's machine is a bit bigger and newer than mine. His is 5.5 hp 24" but I can't find a cross reference to Craftsman 143.025501 in the Tecumseh list.

We expected to find the same low compression as with mine, but on the starter it comes up to 130 PSI. Not a valve issue, I'd say.

The motor will start, run for 15 seconds, then stall. Choke doesn't matter. Spark plug was wet and fouled from repeated attempts at starting. I'm not sure how to proceed with this one. What would you guys look for next?

TIA


----------



## Shryp

For yours, get an impeller kit.

For his, maybe check for spark? Try a new spark plug?


----------



## classiccat

Dave C said:


> ...*Thanks muchly* for the help and guidance on SBF. ...
> The motor will start, run for 15 seconds, then stall. Choke doesn't matter. Spark plug was wet and fouled from repeated attempts at starting. I'm not sure how to proceed with this one. What would you guys look for next?
> 
> TIA


That's what it's all about Dave!!!!! Thanks for reporting back!!!

When the chamber is flooded. 


shut off the fuel & drain the carb bowl.
Remove the plug from the head, keep the plug disconnected from the plug lead as you don't want spark while you do this (_I go 1 step further and ground the plug connector but that's mostly carryover from working on outboards to prevent spark & protect your ignition coils_.).
away from any other ignition sources, crank the engine over a few times to blow-out all of the fuel...you'll quickly see why you don't want spark.
Either clean the plug in seafoam or carb cleaner...or replace it (_I'd just replace it since it could be the cause of the problem_).
The cause of the fouled plug could be a number of things: intermittent spark (_bad ignition coil, coil too far from flywheel magnet, bad plug_), carb running too rich. Assuming it's a Tecumseh, I would reset the carb (_1 1/4 turns-out on the idle jet {side of carb} & 1 1/2 turns-out on the main jet {bottom of the carb}_) then tune it once the engine gets back to temperature...if it lets you get back to temperature.

+1 on the impeller kit


----------



## Dave C

We replaced the fouled plug and managed to get the motor to start, but as I said it stalls after a short time. Given that the plug was wet, it appears to be getting fuel. Even so, I'm ordering a new carb for it (only 18 bucks on Amazon).

These motors have electronic ignition. How much of the motor has to come apart to check the sensor gap?

Thanks again. This place is awesome.


----------



## Normex

Dave C said:


> These motors have electronic ignition. How much of the motor has to come apart to check the sensor gap?


 
To access your coil you have to remove your pull cord casing and then remove the flywheel. Sometimes the flywheel may need some coaxing with a puller so report if it is too hard to remove. Good Luck


----------



## Shryp

Normex said:


> To access your coil you have to remove your pull cord casing and then remove the flywheel. Sometimes the flywheel may need some coaxing with a puller so report if it is too hard to remove. Good Luck


I believe all the electronic ignition ones have the coil outside of the flywheel so don't have to do that.


----------



## Grunt

Dave C said:


> These motors have electronic ignition. How much of the motor has to come apart to check the sensor gap?


The recoil shroud has to be removed to access the ignition coil and the coil to flywheel gap is .012 to .015 thousandths. Most people use a business card as a feeler gauge.


----------



## suspicionofignorance2

Unless you suspect work has been done before on the ign coil...I would not bother it now...Install the new $18 carb...prob find the eng runs fine.,.,!


----------

