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Problem starting B&S engine on a craftsman mower

#1

V

Vintshave

I have the mower shown below. It’s been sitting for awhile. The throttle control cable is broken and the cable that attaches to the front drive wheel control is slack. I keep pulling the rope with gas in the tank and it won’t start. If I spray starter fluid into the air intake it starts and then quickly shuts off. Any advice would be welcome.
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#2

B

bertsmobile1

Pull the rocker cover off and rotate the engine, check that both the inlet ( lower ) & Exhaust ( upper ) valves are moving in & out
Go to outdoor power Equipment site and find the instructions for cleaning your carb then follow the instructions


#3

V

Vintshave

bertsmobile1 said:
Pull the rocker cover off and rotate the engine, check that both the inlet ( lower ) & Exhaust ( upper ) valves are moving in & out
Go to outdoor power Equipment site and find the instructions for cleaning your carb then follow the instructions
Click to expand...

If it was a valve problem, wouldn't it fail to start with starting fluid as well as gasoline?


#4

B

bertsmobile1

Depends upon how much of a problem it is .
A sticky exhaust in particular will run if you shoot starting fluid down the carb
An inlet valve stuck partially open may also run a few seconds .
You can start with the carb then go to the valves next if a carb clean does not do the trick.


#5

V

Vintshave

I'll try that. Also, can you tell me what cable I would need to replace the twist tie I'm currently using for the throttle? I'm also curious why there is slack in the cable that controls the power drive. Could the fact that I can't pull back on the bar (since the cable is not attached to it) be triggering some kind of auto engine cutoff?


#6

V

Vintshave

OK, I replaced the following parts:

Drive cable
Throttle Cable
Filter
Springs
Carburetor
Spark plug

After I replaced the carb (which was very corroded), the mower started on one pull and I was able to mow for about a minute before it cut out. I couldn't restart it. Damn.
Since the mower was sitting for some time, I replaced the spark plug. Started right up. Ran for about 30 seconds and then cut out. Couldn't restart it. Damn again.
In both instances, I shot starter fluid into the carb after it died. Nothing at all. Didn't even restart for a few seconds.

At this point, I'm at a loss - mentally and financially. I can't imagine what else it could be. It ran - albeit for a short time. What should I be checking next?


#7

S

seattlepioneer

Vintshave said:
OK, I replaced the following parts:

Drive cable
Throttle Cable
Filter
Springs
Carburetor
Spark plug

After I replaced the carb (which was very corroded), the mower started on one pull and I was able to mow for about a minute before it cut out. I couldn't restart it. Damn.
Since the mower was sitting for some time, I replaced the spark plug. Started right up. Ran for about 30 seconds and then cut out. Couldn't restart it. Damn again.
In both instances, I shot starter fluid into the carb after it died. Nothing at all. Didn't even restart for a few seconds.

At this point, I'm at a loss - mentally and financially. I can't imagine what else it could be. It ran - albeit for a short time. What should I be checking next?
Click to expand...


I'm currently experiencing the problem you describe with a similar engine and the same carburetor.

I replaced the carburetor with a $14 Chinese knockoff, and the same problem continues. If I prime the engine, it starts fine but then quits running after a few seconds.

Sounds like no fuel to me.

With a new carburetor on it, my next step will be to replace the fuel line, which has a fuel filter in it which could be plugged up or otherwise defective. In any case, it's an old mower and replacing the fuel line is worth while maintenance in any case.

If that doesn't work, I'm going to suppose that the new carb is no good. I bought two $14 carbs, so I have another one to try out.

Those are my best ideas so far.

Oil, fuel, air filter and such seem OK, and the mower starts fine when primed. So my operating assumption is that the engine is not getting fuel.


#8

Scrubcadet10

Scrubcadet10

Run it with the gas cap loose...May not be venting properly.


#9

K

keakar

check the valves and test the spark plug is working since a plug can just go bad like that sometimes

if it does start with starter fluid 99% of time you have no spark

also i think the fresh gas could have loosened up varnish in the gas tank from sitting all that time and that may have sludge gummed up your new carburetor in the short time it ran, but it should still have started with the starter fluid


#10

S

seattlepioneer

keakar said:
check the valves and test the spark plug is working since a plug can just go bad like that sometimes

if it does start with starter fluid 99% of time you have no spark

also i think the fresh gas could have loosened up varnish in the gas tank from sitting all that time and that may have sludge gummed up your new carburetor in the short time it ran, but it should still have started with the starter fluid
Click to expand...

Thanks for your comments.

The fuel line had a filter in it, but I've supposed that a partially plugged filter might impair fuel flow, and in any case the fuel line was old. so I replaced it.

I then inspected the fuel tank, which I found to be contaminated with crud. I removed the fuel tank and repeatedly added gas to the tank and shook the fuel around to entrain the crud and empty it out until the fuel ran clear.

I tried to clean the new carb, which was a $14 knock off. When I took the fuel bowl off, I noted a couple of areas which were ALREADY corroded through the plating on the bowl. Furthermore, the gasket to seal the bowl to the carb body wouldn't fit once it was removed, having stretched and being notably too large to get it back to fit.

At least now I'm satisfied that I have good fuel to the end of the fuel line.

I guess I'm going to buy a B&S carb and try again.

I've assumed that since the mower will start when it has fuel dumped into the carb that the spark plug and spark must be OK. Is that wrong?

It starts reliably when fuel is dumped into the carb, but after 15 seconds or so that fuel is consumed and the engine stops. Even if I manually open the throttle on the carb, the engine still quits. I've presumed that has been happening because of no fuel.

B&S
12F 802-2021-E1
Code 99062966

Briggs and Stratton carburetor part number 799868


#11

K

keakar

seattlepioneer said:
Thanks for your comments.

The fuel line had a filter in it, but I've supposed that a partially plugged filter might impair fuel flow, and in any case the fuel line was old. so I replaced it.

I then inspected the fuel tank, which I found to be contaminated with crud. I removed the fuel tank and repeatedly added gas to the tank and shook the fuel around to entrain the crud and empty it out until the fuel ran clear.

I tried to clean the new carb, which was a $14 knock off. When I took the fuel bowl off, I noted a couple of areas which were ALREADY corroded through the plating on the bowl. Furthermore, the gasket to seal the bowl to the carb body wouldn't fit once it was removed, having stretched and being notably too large to get it back to fit.

At least now I'm satisfied that I have good fuel to the end of the fuel line.

I guess I'm going to buy a B&S carb and try again.

I've assumed that since the mower will start when it has fuel dumped into the carb that the spark plug and spark must be OK. Is that wrong?

It starts reliably when fuel is dumped into the carb, but after 15 seconds or so that fuel is consumed and the engine stops. Even if I manually open the throttle on the carb, the engine still quits. I've presumed that has been happening because of no fuel.

B&S
12F 802-2021-E1
Code 99062966

Briggs and Stratton carburetor part number 799868
Click to expand...
have you watched the fuel solenoid function with the key before reassembling it? if its not puilling itself down when the key is on no gas will be sucked up through the carb

you can take it off and make sure its working correctly without removing the carb, just be sure to shut off the fuel supply first

most fit 1/2" wrench size but some of the newer carbs use a metric size im guessing is 12mm


#12

S

seattlepioneer

<<
have you watched the fuel solenoid function with the key before reassembling it? if its not puilling itself down when the key is on no gas will be sucked up through the carb

you can take it off and make sure its working correctly without removing the carb, just be sure to shut off the fuel supply first >>

Sorry, I'm not understanding this advice at all.

This mower has a B&S Magnum type engine using a gravity fed fuel supply from the fuel tank to the carb. No solenoid. No key either. (carb part #799868)

I'm guessing that you are referring to a more complex engine with this advice than is the case.


#13

K

keakar

seattlepioneer said:
I'm guessing that you are referring to a more complex engine with this advice than is the case.
Click to expand...
ya, i was thinking you had a riding mower

problem still sounds like restricted or insufficient fuel supply anytime it requires choke to stay running

if you can confirm a good gas stream coming from tank to carb, then trash got in the new carb or its defective and needs replacing


#14

T

Telesis

I would take a moment to pull the flywheel cover and make sure the autochoke components are there and working properly (air vane, thermostat, return spring). I just had a unit like yours in my shop and it had a thick mouse nest under the cover causing the engine to remain in full choke all the time. Without the nest, it ran like a top. [Taryl has a nice YouTube vid on the autochoke system if you aren't familiar with it]


#15

Scrubcadet10

Scrubcadet10

Telesis said:
I would take a moment to pull the flywheel cover and make sure the autochoke components are there and working properly (air vane, thermostat, return spring). I just had a unit like yours in my shop and it had a thick mouse nest under the cover causing the engine to remain in full choke all the time. Without the nest, it ran like a top. [Taryl has a nice YouTube vid on the autochoke system if you aren't familiar with it]
Click to expand...


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