Starting problem due to air in fuel pipe?

[mandy]

Our 2.5 TD Bongo has been starting perfectly, until this morning. Turned key, preheat light went out, tried to start, engine turned over well but wouldn't fire. Called out Britania Rescue (arrived in 20 mins!). Mechanic identified there was air in the fuel pipe, bled the air out and it started first time.

I've given the injection pump a good going over and I can't find any evidence of a fuel leak, so looks like the seals are OK, perhaps!

Has anyone got any sugestions about what could cause this?

[bigdaddycain]

Have you ran out of fuel recently mandy?

[Ralph]

Fuel filter blocked or loose? if yours has
the primer pump on top like ours they are
known to leak air on other makes of car
but never heard of it on a Bongo.

[mandy]

Hi bigdaddycain

no, we haven't run out of fuel recently.

[bigdaddycain]

Oh.. The reason i asked was that if it had been run empty,air can be dragged into the fuel pipes, then get trapped at the injector,reducing the flow of fuel, diesel engines need a high pressure fuel delivery,air reduces, or actually can stop the flow at the injectors.

Ralph made a good point, its just possible that the fuel filter is loose, or is not seated correctly.

To bleed the air, the injectors need to loosened (one at a time) Then cranked on the starter till fuel emerges with no bubbles in it, then repeat for each injector...

[mandy]

Thanks Ralph / Thanks Bigdaddycain

We're going to take the oppotunity to change the fuel filter to see if that sorts it. Thanks for the advice on bleeding the air out.

Although there's no sign of a fuel leek from the seals on the sides of the injector pump, any idea how likely it could be leaking from the seal around the shaft that connects to the cam belt? If likely, would it be possible to detect this with the pump in situe?

Thanks again, all your help is very much appreciated.

[Ralph]

I would change the filter as a starting point, cant remember ever
seeing a pump leaking from the front seal but that does not mean
it cant happen but don't think it would cause air in the fuel pipe,
Stand well back if you are bleeding the fuel system Diesel isn't
good as eye drops, and the injector side runs very high pressure,
it can push fuel through your skin quite easily.
I fill the new filter with diesel before fitting, and would run the Bongo
before taking off the old one so the engine should start easily
and should self bleed any air you let into the system.
Just looked at ours and there is a bleed screw on the side of the filter
housing so after fitting the new filter if you have a pump it's that round
doughnut shaped thing on top of the filter housing you can get most
of the air out of the system by loosening that and pumping fuel through
the filter, Diesel eats tarmac by the way so if you have a nice drive
and all that.

[bigdaddycain]

Very good advice above ralph....

If you do have a leak at the pump mandy,it'll be more visible (as drips) at tickover speed, if you get the bongo to tickover that is! Chances are that the fuel will be running at a faster flow when revved,giving the diesel less chance to show itself leaking as it's whizzing through the pump,hence gravity isn't getting a chance to do it's thing by letting the fuel fall through.