Movano air in fuel lines

Owenmov · Mar 28, 2020

Hi all,
The van has had a problem for about 6 months now and been to 3 garages where they’ve changed the fuel filter.
I’m new to diesels,

it’s 2011 2.3 movano

when running there is a lot of small air bubbles coming from the tank side up to the primer bulb and to the filter, from the filter to the pump there are a lot of bubbles.

If I pump the primer the bubbles stop after the filter. I have checked the o rings on the filter housing and can’t seem to find any leaks anywhere in the engine bay.
After I switch the engine off the fuel from the filter back to the primer bulb makes it’s way back down towards the tank.
I’ve just been under it and when running there is a steady stream of bubbles coming right from the tank the whole way through to the pump.
Any help with any of this would be appreciated?

Mikexx · Mar 28, 2020

My presumption is that air is getting in at the tank connector/fitting/clamp, but that doesn't fully explain why it drains back to the tank.

For clarity, do you mean bubbles travel to the pump on the flow side, or on the return back to the tank side?

Owenmov · Mar 28, 2020

Cheers for the reply. It bubbles to the pump on the flow side, from the filter into the pump.
Not sure if it has bubbles on the return or not I’ll check later

The fuel drains about a foot back past the primer bulb. You can watch it coming out of the filter back into the bulb about 10 seconds after priming it

Mikexx · Mar 28, 2020

Owenmov said:
Cheers for the reply. It bubbles to the pump on the flow side, from the filter into the pump.

Are there bubbles between the tank and filter on the flow side?

On Ford Transits this was often a serious problem. Sometimes the filter housing would have a hairline crack.

Owenmov · Mar 28, 2020

Yes, a regular flow of small bubbles. From where it comes out of the tank to the filter after the filter the bubbles get bigger with some small ones down to the pump.
It struggles to start and a lack of power more so at the lower rpm because of it I think

Movano air in fuel lines

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