Listen for "knocking sounds" coming from the diesel motor of the unit. Check the oil level of the engine. Add more oil to the unit of the oil level is low. Drain and replace the oil and oil filter if the engine oil appears to be burnt or dirty.
Remove and inspect the spark plugs if the engine is having trouble starting or is not running efficiently. Clean each spark plug with a wire brush. Replace any spark plugs that are dark, dirty or appear to be burnt.
Remove and inspect the air filter attached to the motor if the engine is having trouble starting. Locate the air filter mounting bracket and loosen it with a screwdriver to release the filter. Blast air over the filter with an air compressor to clean it and remove as much debris and dirt as possible. Replace the filter if it is too dirty to effectively clean.
Check the amount of fluid in the hydraulic fluid reservoir of the unit to determine whether or not fluid needs to be added. Add fluid if necessary. Inspect the hydraulic hoses of the unit for damaged sections or broken connectors. Replace any hoses and connectors that are damaged.