Service a Diesel Fuel Injection System on a Tractor

Introduction

From time to time it may be necessary to re-bleed the fuel system on your diesel engines. Modern diesel engines may be equipped with automatic bleed systems, but you will still need to rectify the initial problems. A diesel engine will not perform efficiently with dirty fuel or air filters and water in the system.

You may need to bleed a diesel engine after:

• Putting new fuel into the system after running out of fuel.
• Changing bad fuel that contained contaminants or water.
• Changing fuel filters at a regular filter change or changing filters after fuel contamination. (for example, water in the system)
• Fuel starvation due to fuel being turned off at the fuel stopcock.
• Loose joints or cracked and damaged piping in the fuel system let air into the system.
• Water has occurred in the system due to condensation or poor fuel storage.

What You Need

• Ring spanner for fuel filter. Where ever possible, use ring spanners for loosening nuts as nuts are made of soft metal and are likely to be damaged by open-ended spanners.
• Ring spanner for opening the injector pump bleed screws. (different size to above)
• Open ended spanner for injector pipe nuts.
• Non-flammable absorbent material for mopping up spilt fuel.
• Bucket to catch fuel before it contaminates the surrounding soil.
• A donor battery for jump-starting the engine. (the tractor battery may run flat from continually cranking an air-locked engine)
• Clean fuel and a fuel transfer pump.
• Spare fuel filters. (if water contamination has been the problem)

Before you start bleeding the diesel engine:

Refer to the operator’s manual for specific instructions on bleeding your fuel system.
Check for fuel, turn fuel on, check for contaminants in fuel sediment bowl.

Bleeding the fuel filter

Follow the fuel system from the fuel tank to the first bleed screw (A) on the fuel filter, open bleed screw and use the lift pump to move the fuel through until no air bubbles are evident, tighten bleed screw (A). Open bleed screw (B, if fitted) use the lift pump to move the fuel through until no air bubbles are evident, tighten bleed screw (B).
Bleeding the injector pump , follow the fuel system to the injector pump and open the first bleed screw (C), use the lift pump to move the fuel through until no air bubbles are evident, tighten bleed screw (C). If there is second bleed screw on the injector pump bleed it next.

Bleeding number (1) injector

Loosen the injector pipe nut at the inlet to injector number 1 by one or two turns. Turn the key to start the engine, turn the engine over in 10 second bursts with 10 seconds of rest in-between. The engine should fire at about 9 seconds, if not, repeat turning the engine over 3 times. When the engine fires stop it and tighten the injector pipe nut. Restart the engine, check for leaks and that the engine is running smoothly without unusual noises. If the engine refuses to start, check and re-bleed the system.

Working Safely

In addition to the general safety precautions:

• Wear protective clothing and wash your hands after the procedure; chemical additives in the fuel may cause dermatitis or irritate your skin
• Always sit on the tractor to turn the engine over. Don’t be tempted to start the tractor from the ground
• Beware of touching fuel being expelled at the injectors. Injected fuel is under high pressure, and may be forced under your skin; it can only be removed surgically.
• Filter or dispose of contaminated fuel in a responsible way.

Notes on engines

How does a 4 stroke diesel engine work?

1. Air is drawn into the cylinders through the air filter on a down-stroke of the piston.
2. The air is then compressed to produce heat and high pressure on the compression stroke.
3. Fuel is then injected into the head of the cylinder and spontaneously burns in the compressed heated air in the cylinder.
4. The piston is forced down under great pressure.
5. On the next up-stroke of the piston the exhaust gases are forced out and the sequence starts again.

How does a 4 stroke petrol engine work?

1. Air and fuel mix is drawn from the carburettor or injector into the cylinder on a down-stroke of the piston.
2. The mixture is then pressurised on the compression stroke and a spark from a spark plug ignites the fuel/air mix.
3. The piston is forced down under great pressure.
4. On the next up-stroke of the piston the exhaust gases are forced out and the sequence starts again.

How does a 2 stroke petrol engine work?

1.Air fuel mix is drawn from the carburettor into the engine’s crankcase by the vacuum created by the piston on the up-stroke.
2. The mixture in the cylinder is compressed and a spark from a spark plug ignites the fuel/air mix.
3. The piston is forced down under great pressure.
4. At the bottom of this stroke fuel/air mix is pushed out of the crankcase into the cylinder which expels the exhaust gases with positive pressure from the down-stroke of the piston.

Problem solving for a diesel engine

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