I have a Toro ride on mower (riding mower in North America) which I ran out of fuel when it was quite new (<1y) and having put 5l of fuel in the tank, it would not start after quite a bit of cranking.
In this instance, the battery failed. Prolonged cranking can buckle battery plates, or open intercell connecting links, and although this was prolonged cranking, it was not ridiculously long. Perhaps the battery was the real cause of the failure?
Nevertheless, I asked what I could do to prevent this recurring.
Well, with best intentions of never allowing the fuel to get low, it has run out of fuel a few times over 10y and has not restarted quickly, so was primed by injecting fuel into the carburettor hose.
Time for diagnostics
A note, the engine has been run on Ethanol free ULP, no Ethanol, ever.
Is the pump faulty?
This should not be the first question, but after market impulse fuel pumps are inexpensive and it is an easy test.
So, the pump was replaced and the old one dismantled and inspected. It was 2y old, and I was surprised that the valves were not as flexible as I expected… so maybe this is the problem.
Time showed the new pump was susceptible, time to do some logical analysis of the problem.
Is there an air leak that compromises pump performance when it is dry?
It is not easy to access the fuel tank end of the fuel hose, so as a shortcut, the hose was crimped off about 300mm from the fuel tank, the outlet hose removed from the fuel pump and a vacuum test conducted to check hoses, fuel filter, fuel pump.
That revealed a tendency for leaks at hose ends if the hose clamps were not applied over the barb or bulge in the nipple. Otherwise everything was good.
Note that air leaks are insidious, small air leaks may result in the engine running too lean at times, and that can cause expensive damage.
Perhaps that fixed the problem?
No.
A primer bulb
A primer bulb was inserted in the fuel line near to the tank. This allows for manually priming the carburettor after a fuel run-out… minimising long cranking and the risk of battery damage.
A 6mm primer bulb was purchased on Aliexpress for about $5.
Above, the primer was cut into the fuel line and the fuel line length adjusted so the primer bulb in suspended in air to avoid abrasion. The fuel line is zip tied to the wiring harness between filter and primer (not seen here due to the cross member).
The fuel line appears to be 6mm bore or perhaps 1/4″. 13.3mm (3/8 PEX) One-ear hose clamps were used to secure the hose.
The primer works fine, even with just a small amount of fuel in the tank, it takes quite a few squeezes to reach pressure.
One thing it will show is leaks upstream due to ineffective clamps… though note pressure tests the hose fitting in a more demanding way than the normal vacuum mode.