Blowing Fuel Out Intake, No Start

R

repperl

Member
Briggs and Stratton 19.5 hp engine. Blows fuel out the intake when trying to start, never starts. Have taken the carb apart 2 times and cleaned, no change. It do believe it has a bad decompression valve (it locks up when trying to start and I have to block off intake with a piece of carboard to "reset" it). My question is if the decompression valve is bad, could it be enough to blow fuel back out the intake valve? Should I start with fixing the decompression valve or new carb? Thanks,
 
You might also remove the valve cover and crank the engine, and watch the action of your rocker arms. Make sure each one travels up and down about the same distance.
 
Fish said:
You might also remove the valve cover and crank the engine, and watch the action of your rocker arms. Make sure each one travels up and down about the same distance.
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What does it mean if the rocker arms are not traveling the same distance? Valve not seating all the way?
 
One of the cam lobes could be wiped out, i.e. the exhaust valve not opening, and the compression blowing back when the intake opens. Just doing simple tests and observing.

If you could take pics or a movie, then we could all see what you see.
 
Pull the carb off the engine. Speay a small amount of starting fluid in the intake port and try to start. If engine fires up for a few seconds you have a carb problem. If it spits back out the intake port and doesn't start you have a valve or ring/cylinder problem.
I really don't know what you mean when you are resetting something putting cardboard over the intake.
 
Hammermechanicman said:
Pull the carb off the engine. Speay a small amount of starting fluid in the intake port and try to start. If engine fires up for a few seconds you have a carb problem. If it spits back out the intake port and doesn't start you have a valve or ring/cylinder problem.
I really don't know what you mean when you are resetting something putting cardboard over the intake.
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Good point. Or rather, disconnect the fuel line and then start the engine. Another possibility is that he has one of those carbs that has a main jet that falls out easily, and he lost it the first time he went through the carb.
Been there and done that.
 
Hammermechanicman said:
Pull the carb off the engine. Speay a small amount of starting fluid in the intake port and try to start. If engine fires up for a few seconds you have a carb problem. If it spits back out the intake port and doesn't start you have a valve or ring/cylinder problem.
I really don't know what you mean when you are resetting something putting cardboard over the intake.
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The engine has a compression release valve on the cam that helps with starting. (I had a problem with the engine appearing to have a slow start, similar to a bad battery, it would turn 1/2 revolution and stop). It has a new battery and starter performed on the bench. I found online that covering the intake doesn't allow the engine to build compression so that the engine can get turning, "bypassing" the broken compression release valve, then take off the cover so that it can attempt to start as normal. (This fixed that issue)

I just didn't know if the compression release being broken could cause issues of fuel going back out the intake. Since it opens the intake valve to bleed off compression at start.

I will give the starting fluid a shot and see what happens.

Fish said:
One of the cam lobes could be wiped out, i.e. the exhaust valve not opening, and the compression blowing back when the intake opens. Just doing simple tests and observing.

If you could take pics or a movie, then we could all see what you see.
Click to expand...

I already adjusted the valves and I think the rockers were traveling the same distance just from turning it over by hand, but I will check this again and get pictures.
 
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