Focus / CMax 1600ccTDCi - fuel issue / limp home

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Tue 2 Sep 2014 23:09
Focus / CMax 1600ccTDCi - fuel issue / limp home - Forwardloop

Hi

I have read about a possible issue with the fuel filter becoming easily blocked with emulsion, and the car going into limp home mode. This happened to me and with a fuel error coming up on the diagnostic, we changed the filter and all has been OK.

But a later observation has made me question this action and I wondered if you had any views.

The event happens every time as I add my Millers diesel additive following each refill. When I do so, I always trigger a "whoosh & gurgle" when I insert the funnel. It has a misfuel prevention type filler cap.

Clearly there is a back pressure developing.

Might this have been the cause of my problem, not the filter itself? If it ever goes into limp home mode again I shall be testing for pressure release!

Is it an issue for me? How might I get the tank to vent correctly when full to avoid the problem

Regards

Forwardloop

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Wed 3 Sep 2014 00:03
Focus / CMax 1600ccTDCi - fuel issue / limp home - Peter.N.

Are you sure its pressure and not vacuum?

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Thu 4 Sep 2014 01:01
Focus / CMax 1600ccTDCi - fuel issue / limp home - Forwardloop

yes of course its a vacuum (negative pressure)

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Fri 5 Sep 2014 00:28
Focus / CMax 1600ccTDCi - fuel issue / limp home - Peter.N.

I would think that the tank ventilation is blocked, is it OK if the filler cap is left loose?

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Sat 6 Sep 2014 12:30
Focus / CMax 1600ccTDCi - fuel issue / limp home - Forwardloop

My thought too, but there is no "old type" filler cap as such just overall swing flap and a push-aside plate down the filling pipe. That must be a tight fit as it holds the vacuum pressure. You can only release it (as part of the wrong - fuel protection mechanism) by pushing in a tube / funnel stem of the correct width. So it would be difficult to wedge open to ventthe tank this way.

How does the top of the fuel tank vent? where too and how do you get access to it?

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