Lawn mower starts, but that's all it does.

[Racer X]

and neither were DOHC motors.

[lafinfil]

Ok - start with the very basics

The fact that it ran and quit would seem to rule out spark for now - loose plug was a red herring.
The exception would be if the spark was intermittent but that is less likely cause (back shelf that one)

Next up - fuel supply. First thing I would do would be to is to loosen the fuel cap and try that
If the tiny vent is plugged then the fuel will not flow to the carb, If it runs with the cap loosened then
tape a straight pin or paperclip and clean the vent hole.

Next thing to check if that doesn't work is to see if there is fuel actually flowing to the carb. Take a pair of
pliers and squeeze the clip holding the fuel line open and work it back off of the carb. Then remove fuel line
(have something handy to catch fuel) if there is no fuel flowing out the line then
there is a blockage - either a blocked fuel filter or debris in the bottom of the tank. There should be a catch screen in there.

I seriously doubt air filter. I have seen engines that would run on a filter that was blocked solid
(not run well - but run no the less)

Checking the choke operation a good suggestion too.

[Greg]

Okay, it's not the spark plug, as 'fil said. Not the air filter, not the gas cap. I will try checking the fuel line, next.

This is looking like a good, inexpensive investment at this point:

[cbelt3]

My similar mower had the same symptomology. It turned out that the engine valve had gotten loose and basically didn't work properly. But I traded it to a guy for a riding lawn mover (adding $$ of course), so I'm happier.


Alternatively it refuses to work for a guy in a kilt that isn't plaid.

[lafinfil]

cbelt3 wrote:
My similar mower had the same symptomology. It turned out that the engine valve had gotten loose and basically didn't work properly. But I traded it to a guy for a riding lawn mover (adding $$ of course), so I'm happier.


Alternatively it refuses to work for a guy in a kilt that isn't plaid.

Could possible be an intake valve stuck open (especially if it is a Briggs & Stratton) but I'm guessing
a dirty fuel line / tank / filter / tank screen - or possibly a stuck float in cracked diaphragm (depending on carb type)


Greg - what is the make & model number on the engine ?

[Greg]

The label doesn't say what make; it does say:
Model 149.986004
Family STP185U1G1RA

Some Googling points to this manual for Tecumseh motors, but I don't see that family in the pdf..

[testcase]

Stale gas is the most common cause of DOA small engines.

The fuel passages in small engine carbs are very tiny. They easily gum up. Once gummed up, you're not getting any use from that equipment until the problem is corrected.

I'd bet that you left gas in the tank (and therefore in the carb) and, the gas turned stale thus gumming up the carb. Is there a primer bulb on this mower? If so, immediately after starting, press the primer bulb repeatedly; especially as the engine starts to falter. If the priming gets the engine to surge, a gummed carb is the culprit. Sometimes, if you keep the engine running this way (with fresh gas in the tank), after a few minutes as the engine heats up, the gum residue might be dissolved & pulled through the carb by the fresh gas. If you're lucky you'll be back in business without having to rebuild / replace the carb.

Another trick for a gummed carb is to use WD-40. With the air filter off, spray WD-40 directly into the carb and try starting. If it runs that would also confirm a fuel system problem. WD-40 is highly combustible so, be careful.

At the end of the season, change the oil and then, run the equipment until it dies from fuel starvation. Pull the starter cord another dozen times to pull air through the carb thus purging all of the gas. Now, remove the spark plug and pour about a tablespoon of oil down the spark plug hole. With the plug out, gently pull the cord three or four times to allow this oil to coat the valves, piston, side walls etc. Replace spark plug but do not connect the spark plug wire yet. Again, gently pull starter cord until you feel the greatest resistance. You now have the piston at Top Dead Center and, both valves are closed. You have the smallest volume of air in a now lubricated chamber. Now you can re-connect the spark plug wire. Blow some compressed air into the gas tank to purge that of gas vapor. When you next use this equipment, you'll start by putting fresh gas in a clean gas tank. It should start on the first or second pull and, you'll get some extra smoke for 15~30 seconds as the oil burns out from the combustion chamber.

I learned this procedure in a small engine repair class I took almost 20 years ago. Since following this procedure, I haven't had a problem any small engine I used it on

[Greg]

testcase wrote:
If so, immediately after starting, press the primer bulb repeatedly; especially as the engine starts to falter.

BINGO.

Thank you; we'll do everything else you said, too. :-)

[wowzer]

testcase wrote:
Stale gas is the most common cause of DOA small engines.

The fuel passages in small engine carbs are very tiny. They easily gum up. Once gummed up, you're not getting any use from that equipment until the problem is corrected.

I'd bet that you left gas in the tank (and therefore in the carb) and, the gas turned stale thus gumming up the carb. Is there a primer bulb on this mower? If so, immediately after starting, press the primer bulb repeatedly; especially as the engine starts to falter. If the priming gets the engine to surge, a gummed carb is the culprit. Sometimes, if you keep the engine running this way (with fresh gas in the tank), after a few minutes as the engine heats up, the gum residue might be dissolved & pulled through the carb by the fresh gas. If you're lucky you'll be back in business without having to rebuild / replace the carb.

Another trick for a gummed carb is to use WD-40. With the air filter off, spray WD-40 directly into the carb and try starting. If it runs that would also confirm a fuel system problem. WD-40 is highly combustible so, be careful.

At the end of the season, change the oil and then, run the equipment until it dies from fuel starvation. Pull the starter cord another dozen times to pull air through the carb thus purging all of the gas. Now, remove the spark plug and pour about a tablespoon of oil down the spark plug hole. With the plug out, gently pull the cord three or four times to allow this oil to coat the valves, piston, side walls etc. Replace spark plug but do not connect the spark plug wire yet. Again, gently pull starter cord until you feel the greatest resistance. You now have the piston at Top Dead Center and, both valves are closed. You have the smallest volume of air in a now lubricated chamber. Now you can re-connect the spark plug wire. Blow some compressed air into the gas tank to purge that of gas vapor. When you next use this equipment, you'll start by putting fresh gas in a clean gas tank. It should start on the first or second pull and, you'll get some extra smoke for 15~30 seconds as the oil burns out from the combustion chamber.

I learned this procedure in a small engine repair class I took almost 20 years ago. Since following this procedure, I haven't had a problem any small engine I used it on

Use stabil to avoid this problem...I think....

[Racer X]

or run it out of gas every fall.