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Fuel supply/vacuum fuel pumps?

15 years ago

My continuing problem with fuel pumps has not been solved!

I installed a borrowed fuel pump from a friend, who said it had worked on his tractor, until the engine went BANG! So, he loaned it to me.

I installed it today. The engine ran for 20 seconds and stopped, never to start again. It must have been running on the gas in the high tank i had temporarily connected to the carb. The friend had the fittings marked as to what went where. NO run!

I thought the vacuum hose from the dip-stick tube might not be correct, so i made up a different vacuum fitting in the breather canister on the block----NOTHING!!

As of this date, my actions consist of closing the shop, going upstairs for supper, and trying to figure out what to do next. I've tried all configurations of hose connections, looked at some other equipment with the identical fuel pump on them, and---NOTHING!! NO RUN!!

Only thing left, in my mind, is the high mounted, gravity flow fuel tank, with no fuel pump, because the engine ran good when i installed a temporary tank, above the carburetor. Good thing that tomorrow is Saturday! I might get in my truck and go away to pick my banjo with like-minded folks, about 50 miles from here!

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Comments (4)

wheelhorse_of_course
15 years ago
Rusty,

As I said before, you need to

1) Verify you have vacuum - with your thumb over the hose or even listening to the end of the hose.

2) Run the machine on the high tank and see if you can get the fuel pump primed. Maybe you have a clogged strainer. In any case, run it for 2-3 minutes and see if you get gas coming out of the vacuum pump.

If still no go check the breather and compression as I mentioned before. If the breather reed valve is stuck open you will never develop a vacuum in the crank case.

Also, check the pug on the dip stick - does it seat solidly.

Good luck buddy, and have a great weekend :)
johninmd
15 years ago
It sint possible the hoses you are using are too soft and all the vac pulse is wasted by the hoses doing this > () O () O ??
Just a thought..
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bill_in_nc
15 years ago
I erroneously thought that some of the fuel pumps worked off pulsed compression, no reason they couldn't, but apparently all used on small gasoline engines operate off pulsed vacuum. Note: If it was a constant vacuum they would not work because the interruption in the vacuum is what makes it pump.

From a B&S service manual we learn the following: "The fuel pump will prime at 30.5 cm (12") maximum lift. Fuel pump pressure is 0.1 kg cm/sq (1.5 psi). The pump is operated by pulsed crankcase vacuum." NOTE: "THE FUEL PUMP PRESSURE MUST NOT EXCEED 1.5 PSI."

On this particular engine the pulsed vacuum line is connected to the valve cover.
rustyj14
Original Author
15 years ago
I doctored up the side crank-case breather cannister, installing a nipple where i connected the vacuum hose, and: VOILA'! It works great! Now all i have to do is clean the carb and it will be ok! I'm getting some back-fire/ popping from the carb, ostensibly from dirt.
Thanks for the replies! I gleaned some great info from them!
Rusty

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