To change the fuel filter on a Massey Ferguson 135 diesel, the following steps should be taken:
1. Ensure that the tractor is off, and remove the key from the ignition.
2. Locate the fuel filter. It is located under the hood near the fuel tank and is typically a small, rectangular box.
3. Use a wrench to loosen and remove the fuel line connected to the fuel filter.
4. Place a catch pan or container under the filter to catch any spilled fuel.
5. Use a wrench to loosen the bolts and nuts that are holding the filter in place and carefully remove the filter from its housing.
6. Clean any dirt or debris from the filter, the housing, and the fuel lines.
7. Insert the new filter into the housing, re-attach all connectors, and tighten the bolts and nuts.
8. Connect the fuel line and tighten the connectors.
9. Replace the key in the ignition and start the tractor.
10. Check for any leaks and ensure that the fuel filter is working properly.