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Discussion Starter · #1 ·
I've got two YT16 machines, both with Briggs 16hp twins. Both have driven me crazy now over losing their fuel supply. Both have fresh rebuilt carbs and fuel pumps, both have new hoses to the crankcase. Both run fine with a gravity feed fuel supply. What I find is that if I let them sit for a few weeks, they won't restart, the fuel pump won't prime and draw fuel from the tank. Both fuel lines are new, both have new inline filters.
Both have perfect compression and no oil leaks. When they run, they're 100% all day.

Both will crank a brand new battery to death before gas is drawn up to the carb, both are fine if run day to day, even week to week, but let them sit a month, and your playing games getting them to prime. For a long time, I was putting some air pressure into the tank to force the fuel down the fuel line, but that requires having an air compressor handy.

What I was thinking of doing is to add a primer bulb from an outboard inline just before the motor, where I can reach down and prime the carb before trying to start it? What amazes me is that even with a full tank of fuel, fuel won't run from the line at carb level, I have to lower the fuel line to below the front wheel axle level to get fuel to run freely. The tanks, fuel lines, and carbs are all fresh and clean, yet I still have fuel issues.
Are my two the only ones with this problem?

Keep in mind that these also don't get parked with a full tank, their usually down to about 1/8 tank or so when they get parked, I do this partly because of the ethanol fuel concerns and if by chance they're not used for a few months, I don't have 3 or 4 gallons of stale gas to deal with.
 

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1981 Ford 1100 4WD
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880 Posts
I thought the fuel pumps had a built in check valve that is supposed to prevent this, no?
 

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Discussion Starter · #3 ·
I've had three of these carbs apart, I don't see anything that would act as a check valve? Plus, if it were a check valve issue, I'd expect it to drain back faster than over the course of a few weeks. Both of these are fine if I run them every few days or so.
Another point I forgot to mention is that if I forget to choke the engine and it don't fire up right away, I have to also reprime the fuel system. If it starts right away, all is fine. It starts normal so long as I use the choke when cold, if i forget, it loses the fuel prime.

I went round and round with the first one a year ago, I finally found a used carb from a running tractor, replaced the fuel lines and tank, and replaced the pump vacuum hose. But nothing changed. I've got a lesser brand machine that uses the same motor, its tank is mounted similarly, and I've swapped the carbs from the Ford with that tractor and they work fine with no issues, yet it's carb does the same on the Ford.

Is there a way to test the crankcase pulse signal to the pump? It must be there since it runs fine once it's primed?

One thing that concerned me was that I nearly have to lower the fuel hose to the ground to get fuel to flow from the tank, yet the tank is above the transaxle/below the seat. I'd have figured that fuel would flow out as soon as the line is lower than the fuel level in the tank? I've even put a clear fuel hose on the one, I can see gas about 6 inches from the carb, yet the pump won't pull it in unless I lift the rear of the tractor or put some pressure in the tank.

Also, the fuel cap in new, and is vented, and removing the cap makes no difference.

Something that really gets me is that I had another YT16, which came to me with a blown engine, I stuck a Briggs 12hp single cylinder on it, no fuel pump, just hooked up the hose and it ran fine, a neighbor still uses it till this day to pull a cart around his yard. That machine, other than being a bit abused, is the same as both of these I have now. Both of the one's I have now are really clean, well kept, fairly low hours tractors but both sat for many years unused.
 

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1981 Ford 1100 4WD
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880 Posts
I have a Kohler powered LGT. The fuel pump on the Kohler is mechanically driven off the cam. The pump itself contains the check valve.

The fuel line on my LGT run down the frame and up and over some braces before it exits the frame near the engine. Check the routing of the fuel line to see if it has a large loop in it that goes up high in the frame. Maybe you can re-route the line toward the bottom of the frame. This might account for the fuel not flowing when you disconnect the line from the pump.

You could always add a small electric pump, one made for a garden tractor. I've seen them for sale on ebay.
 
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