BLEEDING THE FUEL SYSTEM
PRELIMINARIES
a) Make sure that you have plenty of fuel in the tank (a common cause of needing to bleed the system is running out of fuel in the first place!)
b) Have a manual to hand to tell you where things are. To help in understanding the procedures, typical diagrams for in-line and rotary (CAV) pumps are included below.
PROCEDURE FOR 4 AND 6 CYLINDER ENGINES
1. Vent the fuel system (initially) by priming the fuel lift pump by hand. Firstly open the bleed screws on top of the fuel filter housings and pump the lift pump. It s best to do one at a time, starting with the one nearest to the tank. When you have expelled the air from both, then screw them up (not too tight – they are only in aluminium). You are looking for a squirt of diesel WITHOUT any air bubbles in it emanating from the bleed screws.
2. Next unscrew the bleed screws on the injection pump and hand prime using the fuel lift pump as before. When you have expelled all air from here (note: it isn’t easy to see what you are doing because the injection pump is on the opposite side of the engine from the lift pump, get assistance for this stage if possible) then tighten the bleed screws.
3. This is all you can do using the fuel lift pump. but at least you have got this far without using any of the power in the battery. The next stage is to remove any air between the injection pump and the injectors, and this will require turning over the engine. First loosen the nut on the fuel delivery pipes to one or two of the injectors depending on whether it is a 4 or 6 cylinder engine. If it is a 6 cylinder choose two next to each other, this way the engine will sound less “lumpy" when she tries to fire up. You don’t have to undo the injectors to the end of their threads, just a couple of turns will do, but make sure that the pipe to the injector is off it’s seat by gently moving it from side to side, thus allowing air/diesel to escape.
4. Now turn over the engine with the starter. If it is cold use the thermostart. When the engine attempts to start, for a 4 cylinder nip up the injector pipe, then turn her over again and she should fire up and the other cylinders should sort themselves out. For a 6 cylinder, just nip up one of the injector pipes, then turn her over again. The engine should fire up, running roughly at first; nip up the final injector pipe while she is still running and she will eventually smarten herself up. 5. Let the engine run a bit while you are inspecting those pipes/bleedscrews that were undone to check that they aren’t leaking. And inspect these again over the course of the next 10 engine hours to make sure.
PROCEDURE FOR 3 CYLINDER ENGINES
For 3 cylinder models, there is no need to go through the full procedure above. On 3 cylinder models, proceed as below:
1. Clean out the sediment bowl; wash the gauze (putting an airline over it if available); remove the rubber sealing ring, and clean all surfaces (and replace if required).
2. Replace sediment bowl and screw up the yoke, but not tight, let it fill with fuel until it overflows and then tighten it and wipe the unit clean to detect weeping of fuel.
3. Remove the 2 fuel filters, wash out the lower bowls, replace the ‘O’ rings and sealing rings and fit new filters and tighten down. Fuel tank side of the filter top housing is a 9/16ths hexagon head, this is the bleed off for BOTH filters, just slacken it off and pump the lift pump by hand until fuel is expelled from this bleed-off without any air in it, (you will know when it is right as pumping becomes harder. Tighten the bleed-off at the same time that you are lifting the pump and whilst the fuel is being expelled.
4. Wipe or wash off expelled fuel. The tractor should will start without having to bleed the injector pump. Run the engine at 1100 revs for 5 minutes and check for leaks.
TYPICAL EXAMPLE OF A 4 CYLINDER FUEL SYSTEM (WITH AN
IN-LINE PUMP)
