Bleeding Yanmar Fuel System
I Ran Out Of Fuel... Now my Yanmar Tractor Won't Start!
Difficulty - Easy
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a) If you tried to start your tractor BEFORE bleeding the system or you ran out of fuel- you will need to follow all of the steps below (because you have now introduced air through the pump into the rest of the system).
b) If you are changing your filter, valve, etc and and have NOT tried to start the tractor yet- you can stop after doing step #3 (because the air has not made it through the pump yet and it is easier to bleed)
1- Fill the tank completely full of fuel. This will help add pressure to the fuel system and flush out the air much faster. Don't skip this step- it makes things much easier!
2- Locate the bleeder screws at the top of the fuel filter valve (the part that the fuel bowl is attached to). Open the left screw at the top (10mm wrench) a few turns and wait for fuel to run out. Once there are no more bubbles coming out tighten screw back up and repeat with the screw on the right. This will indicate that the filter is full of fuel. If you did not fill the tank there will typically not be enough pressure to force the fuel through the filter. Do not over-tighten your bleeder screw! This is a very small screw that has a hole through it. It does not take much to twist it off. Note: Some newer models have a fancy (leak-prone) spring-loaded pushbutton bleeder. The same procedure applies... just push the button instead of loosen a screw).
3- Follow the fuel hose up to the injection pump. There will be a small bleeder screw (10mm wrench) on the pump where the fuel line goes in to the pump. Loosen it and wait for all of the air bubbles to come out then tighten. You should be getting straight fuel to your injectors now.
** If you ran out of fuel completely while running the engine or you tried to start your tractor before bleeding the system you will need to continue on through step 7. If you did not try to start the tractor before bleeding the system you can start the tractor normally and go on with your day :) **.
4- Follow the steel lines going from the injector pump up to the top of the engine. Loosen the fitting on the end of the line. Do this on both lines. No Fuel Coming Out? Click here.
5- While sitting on the seat, crank engine at full throttle until you see no more air bubbles coming out of the lines. Do not crank for longer than 10 seconds
at a time, letting starter cool 1 minute between attempts.
6- 2 cycles and you should be ready to tighten the fittings back up.
7- The tractor should start now. Let idle for a few minutes to get out the remainder of the air.
NEVER operate starter for longer than 10 seconds at a time. Allow several minutes for starter to cool before re-trying.
Check engine oil pressure light and temperature light. They should both be off. If the red light is on after 10-15 seconds of running, or the amber light comes on- SHUT OFF IMEDIATELY. You could be causing permanent damage. Locate the problem before running again.
FYI- Why Is a diesel engine hard to start when it runs out of fuel? Diesel engines rely on extremely high pressure pulses in the injector lines. This high pressure is required to make a fuel spray that is fine enough to burn completely. The pulses cause the fuel injector to "pop" (a point where the pressure in the injector line reaches the required level and the injector opens) and sprays a very fine mist of diesel into the engine during the combustion stroke. When the injector line has even the smallest amount of air in it, the air will compress and the required pressure can not be met. The injector never opens and the air can not be purged from the line.
If you are unsure about any of these steps- ask a qualified mechanic!