Xantia 2.1TD air leak

HST · Post by **HST** » 09 May 2006, 19:50

I've finally tracked down the approximate location of a fuel line air leak. On sitting for a while bubbles slowly start appearing from the line going into the Lucas injection pump. I've tried replacing the copper washers on the banjo pipe connection and wrapping the bleed screw with PTFE tape (including covering the hole on the shaft), but still the bubbles form. I've screwed both down as tight as seems appropriate.

Has anyone else experienced this or have any suggestions on how to fix this? It's a pain having to give the bleed pump a few squeezes before starting the car after it's been sitting. The car runs fine once started.

AndersDK · Post by **AndersDK** » 09 May 2006, 20:10

Dear HST -

You have just realised one of the most common diesel problem at all

The fact that you can actually see the air bubbles right before entering the pump does not tell you wher the air gets in. Can be anywhere downstream to the tank.

Since the air is leaking INTO the fuel line - and fuel is NOT leaking out the fuel line - its very bothersome to pinpoint the problem - but you can see its there

First you check all the rubber fuel lines for surface hairline cracks. Try bend the hose various places - then the cracks shows immediately. Replace such hosing as a matter of course.
Next thing to check is the fuel filter housing seals. Any seals re-used at last filter change ? - or no records of a filter change ?

Check the return/overflow rubber lines from injectors back to the pump - and the return lines from pump to to tank. The leak can in many cases work itself backwards thru the pump - especially Bosch pumps are prone to do this.

Finally the leak may as well be located under the body of the car in the rigid (corroded steel) fuel lines. Its in no way limited to where you have easy access to the fuel lines

BTW : banjo couplings are best left untouched. IMHO they never fails or leaks by way of their design.

HST · Post by **HST** » 09 May 2006, 20:34

I replaced the fuel filter a while back, with new seal, which was just before the problem started & had thought that was where the air was coming from till I finally actually saw bubbles coming in from the pump. I'll start checking things downstream. You are probably right, as I can bleed the air out without loosening the nipple (just hand pumping clears the visible air - I just have to find where it's coming out), which probably explains why it runs OK.

Thanks.

BonceChops · Post by **BonceChops** » 09 May 2006, 21:18

HST wrote:I finally actually saw bubbles coming in from the pump.

Are you getting confused by it. Fuel flows from the primer pump, to the connection at the bottom of the fuel filter at the back. It then comes out of the top of the filter and into the pump. Then excess fuel leaves the pump, joins up with the injector leak offs and goes back to the tank. The clear pipes are both before the pump. One is before the filter and one is after the filter. Do you get air in bothe clear pipes or just one?

HST · Post by **HST** » 09 May 2006, 21:38

The air is definitely coming from the injector pump into the clear pipe going into the filter housing outlet. It is that line that fills with air first.

BonceChops · Post by **BonceChops** » 09 May 2006, 22:25

HST wrote:The air is definitely coming from the injector pump into the clear pipe going into the filter housing outlet. It is that line that fills with air first.

I still think you are thinking back to front. The injection pump sucks fuel from the fuel tank so the clear pipe is before the pump not after it. The air you see will go into the pump not come out of it. The return pipe from pump to tank is not a clear pipe. It is a black rubber one (unless someone has changed it) and has a small pipe connected to it very close to the pump that comes from the injector leak off's.

HST · Post by **HST** » 09 May 2006, 23:06

I am not confused at all. The bubbles are coming out of the injection pump BACK towards the filter.... I am fully aware of the way the fuel is flowing - you are the one confused by what I am saying!

BonceChops · Post by **BonceChops** » 10 May 2006, 09:36

So your fuel is flowing from the filter to the pump but the air is flowing from the pump to the filter against the flow of fuel while the engine is running. That is a very strange fault that i have never seen before, I wonder if anyone else has?

NiSk · Post by **NiSk** » 10 May 2006, 10:29

What happens when you dunk a pop bottle under water? Water flows IN and air flows OUT i.e. in the opposite direction to the water flow. Thats just what HST is seeing - not strange at all. And it probably means that the air leak is in the pump or pump unions.

//NiSk

BonceChops · Post by **BonceChops** » 10 May 2006, 10:57

NiSk wrote:What happens when you dunk a pop bottle under water? Water flows IN and air flows OUT

I think the air rises out of the bottle because it is lighter that the water leaving negative pressure in the bottle so the water is in effect sucked in, that is not the same as a pump system. If you put the bottle under water top down the air can not leave the bottle so the water can not fill it.

I think the pump would take the air bubbles into the pump and out the return line. If it is as you say where is the air going to? When you try to start a car after changing the fuel filter without priming the air out, the pump draws the fuel and air though the pump and back out the return line, its the same thing isn't it?

HST · Post by **HST** » 10 May 2006, 11:33

BonceChops wrote:So your fuel is flowing from the filter to the pump but the air is flowing from the pump to the filter against the flow of fuel while the engine is running. That is a very strange fault that i have never seen before, I wonder if anyone else has?

Not when the engine running, when it is left to sit for a while.

BonceChops · Post by **BonceChops** » 10 May 2006, 12:32

HST wrote:Not when the engine running

that makes sense, silly me.
That pipe is not expensive from Citroen. You get the banjo (without the threaded bit) clear pipe and the rubber bit that fastens to the filter. Its part number is 1579C5 and is £9.98 + VAT. I found mine was loose where it fitted to the filter. Try to turn it gently to see if yours is loose. I changed the other clear pipe as the rubber bend that goes to the bottom of the filter was iffy, that is about £8 + VAT. I would fit new copper washers if you change the pipe as they are only pennies each.

HST · Post by **HST** » 21 Jun 2006, 21:45

Well, I never traced the air leak and admitted defeat and took it to a garage. They couldn't find it either!

They did solve the symptoms though, by installing a non-return valve before the fuel filter. It starts fine now & no air is visible in the fuel lines. I don't think they spent too long looking for the leak as the total bill was about thirty quid. And no, it wasn't a Citroen dealer!

AndersDK · Post by **AndersDK** » 21 Jun 2006, 22:10

Good garage !

They found a simple and effective solution - at an affordable price

BonceChops · Post by **BonceChops** » 21 Jun 2006, 23:40

If the non return valve has worked it suggests the leak is after it. I bet it is the fuel filter itself. But who cares it is fixed now