Lawnmower - No Start

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All,

My parents have an older (about 20 years old) Craftsman lawnmower. This is the info that I got off the tag:

Engine Model: 143.985500
Engine Family: STP185U1G1RA
Model #: 917.387270

The customer's complaint is that the mower does not start. The mower was working fine up until last week; but has had a hard start issue for many years. When the mower worked, it usually took 10-15 pulls to start.

The fuel tank has fresh gas. Engine oil is clean and full (and has always been serviced annually). Spark plug isn't new, but my dad said "it's OK," so I should probably check.

Any tips on where to start? I was planning to check the basics (spark, fuel and throttle cable), but could use some tips since I have 0 experience with repairing mowers. Also, any recommendations on where to purchase parts would be great.

Thanks!
 
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I was going to say carb, but not familiar with this engine. Here is a similar model where cleaning carb solved the problem:

Cleaning Craftsman Carb

Your parents are the Customer? Are they going to pay you?
grin.gif
 
Have you removed the carburetor bowl and checked the insides for rust, etc? If you have spark, and clean fuel that's where I'd be looking next.
 
Try starting fluid to see if it starts quick. I would agree with the carb problem. Is there a starting primer bulb ? Try to drain the float bowl as it may have water in it.
 
Check the spark first, since it's the easiest. Make sure it's good and snappy, not a weak yellow spark. Make sure the plug is clean (personally I'd just replace it to start with). Also check the compression to eliminate low compression as the cause of the hard to start problem-since you have the spark plug out you might as well.
If you have good spark and compression, then the next thing to check is the carb. You can either rebuild it (they are quite simple), or you can purchase a new one.
 
Pull the flywheel and check the Woodruff key. It is non-magnetic [aluminum] and can deform when a rock or root has been struck. It will make the motor very hard to start or not start at all when deformed
 
When I took a small engine class about 3 decades ago, the diagnostic procedure revolved around 4 necessities:
-Spark
-Fuel (mixture)
-Timing
-Compression

Spark - a quick and dirty test is to remove the plug from the engine, with plug wire attached, ground the threads to the engine block and pull the starter rope briskly. You should be able to see a bright blue spark. No spark, then try a new plug. Then diagnose the ignition system....wires, coil, etc.. Make sure the "deadman" cable assembly is not grounding out. Don't get "bitten" (volts).

Fuel - a method that always worked for me was to pour a teaspoon of gas directly into the cylinder, install the plug, give a few starter rope pulls. If the engine fires with this direct gas installation, you've determined that there is a fuel delivery problem. A carb rebuild or replacement is always an option. Make sure the carb attachment bolts are tight....air leakage can impede starting. Check fuel lines. Check that the muffler is not clogged....restricted exhaust can prevent starting. Check the air filter - dirty or oil soaked media can prevent starting.

Timing and Compression are more difficult to determine. Sometimes the flywheel key will get buggered up a bit, throwing the timing off. I forget how to check compression, but remember that it is difficult on a small engine. There should be some pressure resistance when you pull the starter cord with plug installed.

The fact that the mower required 15 pulls to start seems to indicate a fuel problem, but be careful not to ignore everything else.

Lots of You tube videos on this stuff.

The diy spark and fuel test above have helped me at least 80% of times. Make sure to ask your parents if anything else happened....i.e. they hit a big rock which might have caused the flywheel key to shear.
 
by the time you took the time to take out the spark plug you might as well just spend the $5 to replace it.
see if the air element is clogged with dirt and clippinga and worth replacing or at least cleaningbiit.

agree to drain the carb, loosen the bolt until fuel atarta to come out then tighten back ip. finally for a craftsman mower i had issues with i put a splash of redline si1 which helped a poorly starting mower.
 
If the starter rope feels normal, you have compression.

If you take off the air filter, you have air.

Buy a $2 can of starting fluid, you have fuel.

Buy a $2 spark plug, you (almost always) have spark.

happy2.gif
 
Originally Posted By: Ethan1
If the starter rope feels normal, you have compression.

If you take off the air filter, you have air.

Buy a $2 can of starting fluid, you have fuel.

Buy a $2 spark plug, you (almost always) have spark.

happy2.gif



+1

Id say dont overthink it, replace the spark plug first.
 
Originally Posted By: Ethan1
If the starter rope feels normal, you have compression.

If you take off the air filter, you have air.

Buy a $2 can of starting fluid, you have fuel.

Buy a $2 spark plug, you (almost always) have spark.

happy2.gif




Basic 101. Good stuff. The last time I had a hard starting push mower I did all that and it came down to the carb. Since I had taken and reassembled passenger car carbs w/o problem I figured why not here? Carb in hand....and that mower never ran again no matter what I did. Out of a half dozen cheap push mowers over the years, it was the only one that got "hard starting disease".
 
OK, I looked it up. It is a Tecumseh.
Those never start as easily as a Briggs.

Don't overlook the flywheel magnets getting weak -
I have found that over time (wow, 20 years?) those darn Tecumseh magnets get pretty darn weak. Tecumseh's are not known for having a really powerful spark.

I never felt they were very strong, even when new.
They can be remagnetized, but it isn't super easy to do.

All of the ignition guts (points, etc.) are under the flywheel.
 
Originally Posted By: 69GTX
The last time I had a hard starting push mower I did all that and it came down to the carb. Since I had taken and reassembled passenger car carbs w/o problem I figured why not here? Carb in hand....and that mower never ran again no matter what I did. Out of a half dozen cheap push mowers over the years, it was the only one that got "hard starting disease".


I have a 4hp Tecumseh on my little Troy-Bilt tiller, and the factory carb was always a problem... it NEVER stayed in tune. I replaced it with a Chinese one from eBay for $10 and it's been running perfect since. Go figure.
 
Originally Posted By: Linctex
OK, I looked it up. It is a Tecumseh.
Those never start as easily as a Briggs.

Don't overlook the flywheel magnets getting weak -
I have found that over time (wow, 20 years?) those darn Tecumseh magnets get pretty darn weak. Tecumseh's are not known for having a really powerful spark.

I never felt they were very strong, even when new.
They can be remagnetized, but it isn't super easy to do.

All of the ignition guts (points, etc.) are under the flywheel.



Never say never. I have customers with Tecumseh mowers and snowblowers. They all start 1st pull. It's all in how they are tuned.

OP: my bets are on the carburetor, especially if it used to take 10-15 pulls to start. I don't think I've ever pulled on a machine more than 5 times before thinking something is wrong with it.

Being a Tecumseh, you can usually buy a carburetor off eBay or Amazon for $20, bolt it on and it will start right up. Much easier than cleaning the carburetor which has a hit and miss chance of working.
 
I wouldnt run a Tecumseh mower if it was free. I would chuck it in the trash personally and get them a newer mower on Craiglist for $60-125.
 
Thanks for all of the help, folks. I checked the mower tonight and confirmed that there is no spark, so we need to start there. I did check the carb (since I was there anyway) and I did not see any obvious issues (all passages looked clean, no rust or sludge in the bowl).
 
Bring it in to the car shop you work at and I'm sure one of the mechanics there can figure it out quickly.
 
Originally Posted By: bubbatime
I wouldnt run a Tecumseh mower if it was free. I would chuck it in the trash personally and get them a newer mower on Craiglist for $60-125.


I have had many Tecumseh engines and each one has had a long(20+ years), reliable lifespan. The ones who don't like them are usually the ones who cannot solve a problem should one occur with one.
 
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