Air getting into diesel - suggestions?

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LW
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Air getting into diesel - suggestions?

Post by LW »

Hi all
95 ZX 1.9TD
This is happening once the car has been stood for longer than about 5 hours. I've checked and the filter housing is full of diesel after this time, a quick squeeze of the primer bulb and diesel squirts out of the the top when the pipe is removed. When I try to start the car it gives a quick cough as if it's about to start then nothing. I have to pump the bulb until it firms up then the car will start after 3-5 turns. I pumped the bulb earlier then left it a few minutes, when I went back it had gone soft again as if the diesel was draining back to the tank but if this is the case I would have thought it would be difficult to start whenever it had been stopped for a few minutes?
So far I've replaced the fuel hose from filter housing to pump (it seemed loose at the connection with the pump) and the leak off pipes, but this hasn't removed the problem. Any thoughts on where and what to look at next?

Cheers
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Post by admiral51 »

Hi LW welcome to the forum :) :)

I had a similar problem on my 1.9TD Xantia and discovered that there was a leak in the fuel line from the primer bulb to filter so replaced with this
Image

It has been known that the primer bulb itself is at fault and it lets fuel to run back to the tank

Colin
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Post by LW »

Thanks colin. There aren't any leaks from the bulb or the pipework. Is there a non return value in the bulb that can fail?
Cheers
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Post by Peter.N. »

If you park on a steep downward slope, so that the tank is above the engine, you should be able to see the fuel leaking out.
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Post by Pleiades »

Inside one end of the rubber bulb, there is a non return valve, this is to stop the fuel running back to the tank.

If you cant find any leaks, then this may be suspect and they are available from most motor factors, as they are used on lots of cars.

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Post by uncle buck »

It's an air leak somewhere....the only way that the diesel can run back to the tank is if air is getting into the system from somewhere!

To test the NRV in the priming bulb try clamping the pipe just before the bulb overnight / 5 hours.... then with the clam still in place see if the car starts...if it does you will have to remove the clamp quickly or it may stall due to lack of fuel flow.

Are you sure the leak off pipes are making a good seal...especially the end blanking plug.....You can have an air leak that will let air in but not diesel out.

Cheers.
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Post by admiral51 »

LW wrote:Thanks colin. There aren't any leaks from the bulb or the pipework. Is there a non return value in the bulb that can fail?
Cheers
Hi LW

Unless you can do as Peter N suggests then you wont see any fuel leaking out.The reason for this is that the fuel is sucked from the tank to the to the fuel pump not pumped from the tank.As this is a vacumn then air will get drawn in and when you switch off as the tank is lower than the pump the air will force the fuel to gravity feed back to the tank.

Yes there is a non return valve in the primer bulb but a length of clear pipe will show up where the air(bubbles) are coming from.

Not sure of the Zx layout but if it has the fuel line with a joiner in it like the one in the photo i would check there :wink:
It wont take much of an air leak to prevent the car from starting :twisted: :twisted:

Colin
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Post by bonnyman750 »

On the bottom left rear of the fuel filter housing, there is a white piece of plastic poking out from behind a star washer. This is the end of a type of sensor in the filter housing. I can't think what it is at the moment (too late at night!!). Try squeezing the bulb until solid then, while looking at the white end of the sensor? at the bottom left rear of the fuel filter housing, keep squeezing the bulb. I had a problem with air getting into the system and it was the 'O' rings on the sensor body which had gone hard and flat and were letting air in. By overpressurising the filter housing it forced diesel out from between sensor and housing, which formed a small puddle on the casting behind it. The cure was to remove the housing from the engine, extract the star washer and pull out the white plastic unit. carefully remove the 'O' rings and take them to your nearest bearing stockists and match them up with new rings, as Citroen only supply the complete unit
Hope this makes sense and it helps you :)

Glyn
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