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post #1 of 10 (permalink) Old 9th June 2010 Thread Starter
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Master 2.5dci air in fuel

My '04 Master 2'5DCi is picking up air in the diesel supply from the tank. question is this....can the air be being introduced by a common point between the return and the supply in the tank. I understand there (is there?) a low pressure pump in the tank. could the fault be that the pump mixes fuel from the return ( thereby including air, if the leak is between the injectors and the tank on the return side) or is the return isolated from the supply completely at the tank end. In which case does the pump become the main suspect? last thing i want to do is drop the blasted tank only to finf the leak is up front somewhere. I cant see a any obvious leaks on the injector returns.
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post #2 of 10 (permalink) Old 9th June 2010
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Re: Master 2.5dci air in fuel

I doubt very much if there is a primary pump in the fuel tank. But check anyway. You should be able to hear it run for a few seconds when the ignition is switched on.
The most common area for air ingestion is usually on the injector fuel return pipes so it may be worth checking that aspect first.
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Re: Master 2.5dci air in fuel

Yeah, I was suspect too, but have seen a number of references to a 'low pressure pump' in the tank!
I've got a manual coming in CD form so we'll see what that reveals.
Thing is, if air is bleeding into the return, how is that finding its way into the up supply from the tank? There must be some point in the tank where the return and supply meet for that to happen. I assumed any air in the return would simply vent into the tank void space??
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Re: Master 2.5dci air in fuel

OK..have now come to the conclusion that the rate of rising air bubble in the line from the tank is minimal. It doesn't explain the large bubble that collects quickly at the clear tube going into the filter housing from the priming pump ( I've changed the filter and seals) suggesting the the bulk of the air is coming up from the injection pump. If the injector returns are leaking that air presumably is in the pump and finds it's way up through the pump and the line supplying fuel to the pump and therefore up into the filter...does that sound possible?
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post #5 of 10 (permalink) Old 10th June 2010
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Re: Master 2.5dci air in fuel

Lots of DCi's seem to have some air in the pipes
unless it's causing problems leave it alone you may
never stop it.
I suspect the air is normal and comes from the injectors via the leak back pipes.

I used to be indecisive, now I'm not sure.

If you find a fix for your problem please let us know it will help others.
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