Bleeding marine diesel systems

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Subject: Bleeding a Volvo aqad31

Tony, I have just put my boat on the water and I am trying to commission the engine, It is an AQAD 31 Diesel. The engine although never been used is dated about 1986, the problem I have is not being able to get any fuel pressure to the injectors.

I have clear clean fuel to the pump, I can bleed the fine filter no problem.

On loosening the pipe into the injector pump then this appears to have a good pressure.

At the injector pipe all I get is a small trickle of fuel, with air.

No end of bleeding does not improve this.

The engine had some residual material in the engine fuel system as it ran OK for some 10 - 20 seconds before diesel was connected.

Questions:

1) Is there any other bleed point that I am missing.

2) Would the substance in the engine be some form of preservative.

3) Could it just be old diesel with diesel bug. If so what damage could it have done. How can I clean the system.

Look forward to your response

Steve

ANSWER

Dear Stephen

First of all I think it ran on some air free fuel or preservative oil that was in the pump from new.

I do not think that you have bled the injector pump. Regrettably I do not know what type of pump is fitted to your engine, but bleeding from the pump inlet is unlikely to remove air from the body of the pump.

I would expect most injector pumps to have a bleed screw fairly high up on the body. If you can locate this loosen it and bleed until no more air bubble come out (like you did the inlet pipe.)

Then loosen (about half to one turn) the injector pipes at the injector end and spin the engine on the starter (it may be worth setting the control to full speed, but it should not be strictly necessary) until fuel start dripping from each union. Tighten each nut in turn and if you have a good battery the engine should start.

If your engine stops by simply turning the key off, turn the ignition on for any attempts to bleed the injector pump or the high pressure pipes..

I hope this helps

Tony Brooks


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