Priming A Lawn mower Engine: What Does Pushing On The Bulb Actually Do ?

[Robert11]

Hello:

When one pumps the bulb the few times that is required when starting the typical lawnmower, etc., exactly what is one doing ?

a. e.g., does the pumping action just draw gas into the bulb, and then the next push on the bulb squirts it into the carb, or... ?

b. If there is gas in the bulb, can one consider the engine "primed" ?

If someone might explain this bulb pumping routine a bit, and exactly what happens, would be appreciative. Realize I really don't understand what is happening

Thanks, Bob

[raven]

I don't know how far along the gas is pushed, but what you're doing is flooding the fuel line (which drains when the engine isn't running) so that you don't have to pull-start the engine or run the starter for a real long time while eating up the air in the line.

John

[Jeff Wisnia]

You are correct John, it pulls fuel up from the tank, but it does actually push fuel into the "carb" bore. If you push it too many times you can "flood" the engine.

Jeff

[Gideon]

Robert,

It has always been my impression that there are 2 types of primers for small gasoline engines:

1) One type primes the combustion chamber by squirting raw gasoline into the fuel intake. 2) The second type primes the carb by pumping gasoline into the fuel bowl.

One crude method of determining the type of primer is by observing the priming instructions. If you are priming the combustion chamber, then you'll be instructed to pump the primer just a few times. If you are priming the carb fuel bowl, then you are probably instructed to pump more times.

A better method is to test the primer while the engine is running. Have another person rapidly pump the primer while the engine is running. Ten very rapid pumps should work fine. If the engine operation is not changed with all of that priming, then the primer delivers gas to the fuel bowl and not to the combustion chamber. But if the engine sputters or stalls, then the primer is delivering fuel to the combustion chamber and the rapid primer while running is flooding the engine with too much gasoline. Often this will cause the engine to sputter and stall.

I've never read any of this anywhere and it is just what I've picked up over the years. I have small gasoline engines which display both sets of behaviors, so I'm a believer that there are 2 priming methods.

Good luck, Gideon

[Rolling Thunder]

Pull off the air cleaner and take a look down the carb while pressing the primer bulb and see what happens. You'll see the gas squiring towards the engine intake.

Thunder

[Bob G.]

=============== I believe all you are doing is pumping air (adding pressure) to the fule tank thus "pushing" fuel towards the carb.... I used to trim my lawn woith a lawnboy walk behind mower and the "bulb" was dryrotted...and did not work....I just disconnected it and when I need to start the engine I just blew a little air into the line and the engine started right up... plugged the line with a golf tee when not in use for years... Got smart years ago and now what my lawn tractor will not cut just does not get cut...

Bob G

[John Frick]

replying to Gideon, John Frick wrote: Awesome measure of accumulated knowledge Gideon, Thank You!

-John