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I've taken the 90 into the garage today to have the brakes done. I aksed them about the woosh of air I get when I open the diesel cap.

They've just told me it's a problem with the diaphragm (sp?) in the fuel injector and that basically I need a new diaphragm as all the turbo is being sent back into the tank and may make the tank explode.

Anyone else experienced this? Will it have meant an increase in fuel consumption and decrease in power?

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Aye if it's sucking air in it's definately not the turbo pressurising the tank, or some other bull.

Blocked breather in filler cap, unless there's so much vacuum you can't get the cap off I wouldn't worry about it.

I wish mine was blocked I lose (much needed) petrol when mines on a steep side slope :o

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Am i right in saying that the tank is pressurising?

This shoudn't happen because there are breathers that allow the tank to,ahum, "breath"

So your breathers are blocked.

If theres no detrement to the running then i'd have it back and sort the breather pipe myself.

If there is a problem with the running then it could be the pump but i'm not convinced because the fuel return is a gravity system.

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I wouldn't know where to start though and these guys are not going to look at the breather because they say that's not the problem.

Also they say that as the tank's pressurising it will go pop at some stage

Who's vehicle is this theirs or yours? Tell them you want the breather checked first :)

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What sort of engine is it - I'm assuming a 300Tdi in what I say here:

I may be wrong but I can't immediately see how a leaking 'fram would pressurise the tank anyway. There is no diesel inside the compensator unit on either side of the diaphragm so an increase in pressure inside there wouldn't do anything unless it is blowing through other seals inside the injector pump - and in any case there is a breather pipe out to atmosphere from the bottom side of the diaphragm anyway so excess pressure would vent out through that (little short rubber thing on the back of the pump). Also you would lose LOADS of power if the diaphragm was leaking that badly, and if it was pressurising the fuel lines it would probably also put air into the fuel which would stop the engine....

Lots of reasons why I regret to advise I think they are talking blx :)

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Actually, I'm not convinced that they are talking bull.

I've heard of this before - it's peculiar to the TD engine - and in fact used to happen on my own 110 when I had the TD fitted. The fuel tank pressurises and blows fuel out from around the breather in the cap - there is a definate blowby when the fuel cap is removed.

It no longer happens now I have a TDI :D but I do recall seeing a thread about this same thing on this forum some time ago - just can't find it at the mo. There was a mention of a diaphram in the fuel (injector) pump being the cause - and a rebuilt pump being the solution.

If I can find it later I'll put up a link.

Matt

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On TD injector pump, if the boost valve diaphragm has got a leak it will presurise the tank to some degree as the diesel return line to the tank is on the opposite side of the diaphragm to the boost air. With a bit of care the diaphragm can be changed without taking the pump off. :rolleyes:

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On TD injector pump, if the boost valve diaphragm has got a leak it will presurise the tank to some degree as the diesel return line to the tank is on the opposite side of the diaphragm to the boost air. With a bit of care the diaphragm can be changed without taking the pump off. :rolleyes:

What a stupid design! :rolleyes: :rolleyes: :rolleyes:

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I'll be in Stroud on Sunday if you want a swapsie fuel cap to experiment with. In fact I suspect if you PM TroddenMasses and offer wine or beer he might lend you one on a longer term to supplement his alcohol habit :)

Even if there is some problem with the injector pump, surely the first line of attack (and the cheapest) is to deal with the breather which is presumably blocked otherwise it would capable of venting the extra air? And if the breather IS blocked then it is not also possible that temperature changes could cause the tank to get pressurised/evacuated?

Rog

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