Bleeding Air Out Of Yanmar Tractor Fuel System

If you run out of fuel or try to start your tractor without bleeding the fuel valve- you probably have introduced air into the fuel system and are having trouble getting the tractor to start again. DO NOT USE STARTING FLUID! You just need to bleed the air out and that is a pretty simple task. 

• Be sure tractor and PTO are in neutral. 
• Fill the fuel tank completely full of fuel. This will help add pressure to help push the fuel along. 
• Loosen the bleeder screws on your fuel filter valve and wait for the fuel bowl to fill completely and all of the bubbles to leave.
• Tighten those back up and then loosen the bleeder screw on your injection pump and do the same thing. Wait for all of the bubbles to leave.
• Now, with any luck, your tractor should start. If it doesn't then the air has pushed into the steel injection lines and we need to get it out. 
• Loosen the nut on one of the steel injection lines where it screws onto the fuel injector. Just pick one. No specific order needed. Just loose- not off.  
• Move the throttle to 'full throttle' position. Crank the engine over and watch the tiny spurts of fuel. It might only be a teaspoon or less per squirt. Crank over until there are no more bubbles (usually 10 seconds or so). Do not crank the starter more than 10 seconds without a nice break to cool. Using the decompression can help the starter out. 
• Tighten the nut (do not overtighten) and move on to the next injector. 
• Repeat this process for each injector. 
• Restart the tractor. 

If the tractor still will not start then it is possible that you had water in your fuel and the tiny pump pistons have flash rusted and are stuck in the pump's cylinders. This happens when you run out of fuel and there is no diesel to keep them lubricated. It can happen very quickly. To remedy, try tapping on the side of the pump while you are cranking over the engine. Just light taps with a small hammer... you are not trying to teach it a lesson. This should knock the pistons free and allow the pump to start working again. 

"So why is air such a problem? I run my push mower out of gas all the time and it starts right up".  Air compresses, fuel does not. The diesel engine in your Yanmar depends on non-compressible liquid in order to squirt the fuel at incredibly high pressures. The injectors are calibrated to only open at a fixed pressure (around 2,600psi). If the fuel is allowed to compress then that pressure is never reached and the injector does not open and the air can not be purged. The only way to fix the situation is to manually let out the air.  

If you continue to have problems feel free to contact us.