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HWhite
HWhite

Posted: Sun May 12, 2019 7:00pm

Post Subject: Bleed Injector Fuel Pump

I have a Perkins 4.108 with a Lucas CAV pump. I think there are two bleed screws on it, but I am unsure where they are. I think on is above the name plate. Do you have any ideas where they are and what is the best way to bleed the pump. Thank you. Hugh White

Bleed Injector Fuel Pump
Tony-B
Tony-B

Posted: Mon May 13, 2019 6:14am

Post Subject: Bleed Injector Fuel Pump

As the forum software reduces images to a size that is unusable and I don't have your email address I can not send you a diagram. Look on the cylindrical cast aluminium pump body. There is a position for a bleed screw on both sides at about the 10 o’clock and 2 o'clock positions. One will have a simple hexagon head. This is just a blanking plug and is bets left alone. The other side will have a larger hexagon (say about 11mm) with a smaller 8mm hexagon head in the centre. The smaller 8mm one is the bleed screw. Make sure the larger hexagon does not loosen when you try to undo the 8mm bleed screw. Bleed this one first for at least 30 seconds AFTER you think you have all the air out of it and the n bleed the injectors and try to start it. If it won't start re-bleed the side screw and then look at the throttle and stop levers between the two and slightly offset to one end of the pump you will see another 8mm hexagon possibly set into a larger hexagon that is locked in place by yet another nut. Not all injector pumps are like this but if yours is apart from the 8mm bleed screw the other stuff is an idle stabilisation damper that you do not want to mess with. The damper assembly is also often glued into the pump turret so you must not wrench the whole assembly out of the pump. Bleed from the 8mm hexagon if it would not start but after re-bleeding the side position. If yours is an older hydraulic DPA pump there will not be an idle damper and the idle adjustment is a slotted knurled screw with a spring around its shank like a carburettor adjusting screw. It is just possible that your engine has a mechanical DPA pump and that is different in that it is a bit longer and instead of a turret it has a rectangular box with the throttle and stop lever sitting on the top. This has a bleed screw on it similar to the one on the side of both pumps. Use the lever that is under the fuel lift pump to pump fuel from the tank into the system. Long slow pumps are the order of the day. First bleed the top of the fuel filter on the engine. I think there is a banjo bolt you can loosen with the injector leak off pipe joined to it. If you have a primary filter or water trap between tank and lift pump bleeding from the filter will take ages so try to see if that primary filter/water trap will bleed itself by gravity before anything else. Then the engine filter then the injector pump, then loosen about a turn all the LARGE nuts on the injector unions and spin the engine on the starter until fuel drips from the unions. Tighter them and it should start. If no fuel drips or it won't start bleed the rest again. Never be too keen to close off a bleed point. slugs or air can be trapped in the pipework.

Tony-B
Tony-B

Posted: Tue May 14, 2019 5:32pm

Post Subject: Bleed Injector Fuel Pump

Hugh sent me a photo via the Canal Boat office but any question that requires images will better sent direct to me Tony@tb-training.co.uk. As I mentioned in my reply his particular engine might have a mechanical DPA pump that is rather different to the Hydraulic ones I described. I have sent Hugh an annotated image of his pump that identifies the bleed points. The bleeding procedure is the same as for the Hydraulic one apart from not having to worry about using the top bleeds point and doing collateral damage. The question and a ssuitable answer will be submitted to the magazine and if they decide to publish it you should see it around July/August.

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