Vintage Tractor Engineer

Different models of tractor obviously have slightly different fuel systems, but all types need to be free of air in the fuel system for it to work efficiently. Most vintage tractors have the luxury of a fuel tank fitted above the engine (unlike many classic or modern tractors), this gives the aid of gravity during the bleeding operation.

Normally the fuel system consists of a tank followed by a glass sedimentary bowl, lift pump, one or more fuel filters, injection pump and then high pressure lines to each injector. There may also be a connection to a thermo-start device (manifold heater).

1. Make sure there is sufficient fuel in the tank and that the fuel taps are turned on (believe it or not this has been overlooked before!)
2. The first task to remove the air is to open the bleed screws on top of the filters and pump the lift pump until clean bubble free fuel is expelled. Close the bleed screws in turn, whilst maintaining a small fuel flow with the lift pump.
3. Next, identify and open the bleed screws on the injector pump (there may be more than one). Pump the lift pump until clean bubble free fuel is expelled and close the screws in turn as they run free of air.
4. Undo one or more injector pipes at the injector end. With the stop control in the run position and the throttle wide open, turn over the engine on the key until fuel can be seen pulsating from each pipe. The pipes can then be re-fitted.
5. If a thermo-start is fitted, the fuel line must be slackened and bled by pumping the lift pump.
6. The tractor is now ready to start. If you are unsuccessful, there may still be air in the system and the procedure must be repeated.

Beware, in step 3 the fuel is potentially under extreme pressure. There is a danger of the fuel entering the skin and causing blood poisoning.

An inability to bleed the system could be caused by any one or a combination of the following.

• Blocked pipes
• Blocked filters
• Inoperative lift pump
• Frozen or waxed fuel
• Split suction pipes allowing air in
• Damaged injector pump
• Sheared injector pump drive

Sometimes it is necessary to turn the engine to a different postition to allow manual operation of the lift pump.

Watch a video of how to bleed a tractor fuel system in the window below.

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If your internet connection will not run this video, then see how to bleed the fuel system here.

When fitting screw clamp type battery terminals to the leads it is important to get a good contact between the terminal and the lead. The problem is that when the clamp screws are tightened, the wires tend to spread out which results in a poor electrical connection and hence an inefficient transfer of power when under starting load.

An improved connection can be achieved by running solder into the wires before the terminal is fitted, as shown in the photo below. This will make the end of the cables rigid, allowing the clamp screws to take a firm hold. If this has not been done, then the connection is more likely to deteriorate and could be the cause of poor starting performance.

Care is needed during the soldering to make sure that the insulation is not damaged. The correct flux should also be used. Beware, due to the conductivity of copper, the heat will travel quickly and a long way along the cable.

When the new cables and terminals are fitted, anti-corrosion gel should be applied to the exposed metalic surfaces around the battery terminals to prevent corrosion.

Remember, many battery terminal clamps need a spanner size of 5/16ths Whitworth. This is indicated when both 1/2in AF and 13mm spanners are too small, whereas 9/16in AF and 14mm spanners are too large. There is no need to overtighten the clamp bolt if all the surfaces have been cleaned before connecting. Do not clean the battery posts using a wire brush as this can cause sparks and thus an explosion of the hydrogen gas in the battery.

Other areas to check on the leads are the insulation on both leads and the integrity of the terminals on the starter motor and earthing point.