How Do I Bleed My Yanmar Tractor Fuel System?

We want to help you bleed your tractor fuel system safely and effectively.

If you do not feel that you understand these steps, or can perform them safely, consult your tractor dealer or local mechanic.

First --- if you tried to start your tractor before you bled the system --- OR if you run out of fuel --- you will need to follow all the steps we are giving. This is because you have introduced air through the pump --- that is now in the system.

IF --- you are changing your valve and filter and have not started your tractor --- you can stop after the third step. This is because air has not made it through the pump.

Let’s go through the steps:

(1.) Fill your fuel tank. This adds pressure to the fuel system. Therefore, you can flush air out much quicker.

(2.) Locate the bleeder screws. They are at the top of the fuel filter valve. This is the part that attaches the fuel bowl. Open the left screw at the top (10mm wrench) a few turns and wait for the fuel to come out. Once it stops bubbling, tighten up the screw. Repeat with the right screw. The filter should now be out of fuel.

(3.) Follow the fuel hose up to the injection pump. You will see a small bleeder screw (10mm wrench) on the pump. This is where the fuel line goes into the pump. Loosen it. Now, wait for the air bubbles to completely come out. Then tighten it again. You should be getting straight fuel to your injectors now. Do not over-tighten the bleeder screw. This is a very small screw. It has a hole through it and does not take much effort to twist it off. Some newer units have a spring-loaded push-button bleeder. Follow the same procedure --- just push the button instead of loosening the screw.

NOTE: If you run out of fuel while running the engine. Or if you tried starting your tractor before bleeding the system, you will need to go through step 7. If you did not try to start your tractor before bleeding the system, you can now start the tractor. (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.

If you have no fuel coming out you need to note that it is common for injection pumps in tractors that have water in the fuel, to stick when setting, or when it ran out of fuel. The injection pump has a tiny plunger on each cylinder. It is spring-loaded. When the cam pushes them up, they squirt fuel. When the cam turns more, they fall. When there is water in the fuel, or you run out of fuel completely, the cylinders can stick or 'flash' rust slightly and the ultra-tight tolerances in the pump get very tight. When the plunger goes up, it gets stuck. The spring is too weak to push it down. The cam just spins and neither makes any contact with the plungers or just barely moves them, pumping little fuel. Here’s what you can do. A gentle tap of a hammer, on the side of the pump mounting flange, while cranking the engine, will frequently loosen the plungers. The pump will start to work. Serious issues may require the pump to be removed and rebuilt.

(5.) Sit on the tractor seat and crank the engine. Crank the engine at full throttle until you see no more air bubbles coming out of the lines. Do not crank over 10 seconds at a time. Let the starter cool down for at least a few minutes between attempts.

(6.) Tighten the fittings back up. You should be ready after 2 cycles.

(7.) The tractor should start now. Let the engine idle for a few minutes to get all the air out.

NOTE: Never crank the starter for longer than 10 seconds at a time. Allow the starter to cool down for several minutes before re-trying. Check your engine’s oil pressure light and temperature light. They should be off. If the red light is on after 10-15 seconds of running, or the amber light comes on, shut the tractor off. You could be causing permanent damage. Locate the problem before running again.

You may be wondering why a diesel engine is so 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; fine enough to burn completely. These pulses cause the fuel injector to "pop." This is the point where the pressure in the injector line reaches the required level to open the injector. Then it sprays a very fine mist of diesel into the engine during the combustion stroke. When the injector line has air in it --- the air compresses and the required pressure is not generated. This means the injector cannot open and the air cannot expel from the line.

If you need any further help or have any questions about fuel systems, tractors, or anything else, please contact your dealer, local mechanic, or call us at 602-734-9944. Please ask about our current new and used tractor supply.

Team Tractor Ranch – #1 Tractor Dealer in Arizona. We sell and service most major brands of tractors including Yanmar, Kubota, John Deere, TYM, Mahindra, Kioti, Case, New Holland, Massey Ferguson, Ford, Deutz, Case IH, Farmall, International Harvester, Branson Tractors, LS, Shibura, Claas Tractor, McCormick Tractors, Valtra, Solis, YTO, Montana, and Nortrac.