Ianmcd

Mk2 focus starts then dies

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hi,

Looking for help with my 2010 1.8tdci focus.

After the car has been sitting a while (overnight) when i start it up it idles for a few seconds then dies. Its like the fuel drains from the lines and so whatever is left in the filter is only enough to start it and idle for a couple of seconds. Iv had the filter and seals replaced with no resolution. I put a non return valve on the line and it didnt help

The only way i can get out in the mornings is by pumping the fuel back into the line via the purger thing on the non return valve.

Any help appreciated 🙏 

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We had a Qashqai with the same symptoms, turned out it was a split in the primer bulb letting air in. 

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Yes, this is characteristic of Diesels letting air into the priming circuit. I have had it with Mercedes and once got a very good Citroen BX turbodiesel estate for free that I kept for four years and 75,000 miles as the daily car which had been retired at 120,000 miles for just this problem. You've got something perished, chum. Look for diesel seepage all the way back to the tank. It may take a bit of finding but it will be a cheap and certain fix.

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Iv not noticed any leaks on the driveway, would this not be a tell tale sign of a leak somewhere? 

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No. Air is getting in. Any seepage will, if it can be seen at all,  be very small. Changed the fuel filter lately? Can be the pipes leading  into that or the seal around it. You are talking about a couple of cc of air being pulled in overnight. The leak will be small. A piece of clear pipe is often useful to view the flow and spot bubbles  and changing the primer bulb might fix it if the valve within is leaky. There are two fuel lines. A supply line and a return line which is why a non return valve rarely fixes this problem.

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Hi, thanks for your help. The Fuel filters been changed by garage, and they said they changed seals too. Where is the primer bulb located? Would you use the clear tube in replace of the supply line?

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is the leak most probably going to be in the supply line?

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1 hour ago, Ianmcd said:

Where is the primer bulb located? Would you use the clear tube in replace of the supply line?

Mean old Ford rarely fit primer bulbs. Many other makes do, but as far as I know, only the Transit has them of Ford's uk vehicles.

A bit of clear tube, as long as it was rated for diesel use and engine bay temperature, would allow you to see if air got in that section.

The leak is unlikely to be under the car. When the tank is full, those pipes are below the fuel level, so would seep out a bit of fuel, that you would see on a suitable, clean surface. But it could be on either side of the filter, within the engine bay, anywhere where the pipes are above the fuel level in the tank. Bending the hoses a bit will usually identify any brittle or weak sections.

The only certain case I have heard of of a leaky hose was on a Mk1 Focus, and it was the one from filter down to the pump.

It is just possible it could be in the return lines, but the air would have to get back into the pump. If your non-return valve is working,it should prevent that from happening as the fuel in the feed to the pump can not escape back to the tank to allow the air to flow back into the pump. But leaks in the feed lines on either side of the valve will allow air in, as fuel can be drawn through the pump just by gravity (slowly), allowing the air in as the fuel returns to the tank via the return pipes.

I think the whole high pressure part of the system can be regarded as a sealed dead end, with no possible leaks. They would be very obvious if there were any, unless through the injectors. But an injector leaking with a tiny pressure of gravity would fail dismally at full operating pressure, almost certainly.

 

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Garage said they pressurised the tank and found no issues with pressure dropping but im beginning to think they didn't now because surely it wouldn't of held pressure if theres a leak somewhere which from what im reading it certainly suggests there is

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59 minutes ago, Ianmcd said:

Garage said they pressurised the tank and found no issues with pressure dropping

That is a very crude and imprecise test, it will not find small leaks. I have done a lot of pressure testing of all sorts of stuff in the last 30 years or so.

The tank is large and flexible, it would have to lose a lot of air or fuel before you could measure a pressure drop in it. Temperature changes would have a greater effect than a tiny leak.

17 hours ago, Ianmcd said:

The only way i can get out in the mornings is by pumping the fuel back into the line via the purger thing on the non return valve.

If re-priming the fuel system allows the car to re-start reliably, then air getting in is the most likely culprit, by far.

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20201006_104120.thumb.jpg.ab566f4b827eda8e795c825f90fbb737.jpgThank you. And your saying most likely the leak is in or around the filter either before or after? Il just have a good look around in there and see can i spot anything

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11 hours ago, Ianmcd said:

Il just have a good look around in there and see can i spot anything

I am quite glad you posted that picture. I have a priming bulb that looks a bit like the one in the photo, and it leaks like a sieve! Neither of the non-return valves in it really seal, and it is prone to leaks at the ends. The plastic moldings in my one are very poor quality, with steps and flash at the mold join lines. I use it to prime the system after a filter change, but remove it once done. I do a have a permanent, good quality metal valve in my system that prevents fuel running back to the tank while I remove the primer.

Yours does look better quality than mine though, mine did not even have the metal clips at each end. However if there are no visible cracked, hard or perished bits of pipe in the engine bay, I would suspect the bulb of allowing a bit of air in. Also that type of bulb does not always have springs in the non-return valves, and relies on gravity or back pressure to close the valve. My metal valve is spring loaded, so works any way up.

Photos of the valve I used and my bulb are here:

 

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Yes but the problem had occurred before the primer bulb was fitted. Mechanuc tought that if there was a crack somewhere in the line that by fitting the non return would stop the fuel returning from the filter overnight. So problem was there beforehand and i must say the non return did work for about a week but then back to square one

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Seems to happen more regularly when i have less diesel in the tank, maybe i should just keep the tank full 😅 

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