Banjo bolt on carb gone.

[Andyww]

Had a look at the engine this morning and found one of the banjo bolts which connect the inlet plenum to the top of the carb has completely disappeared!

Spent the rest of the morning hunting for it , removed the undertray, its nowhere to be found. I guess it must have unscrewed and got blown out by boost pressure.

So this leads me to wonder: Exactly what is the function of these connections? I can think of two possibilities:

Do the connections supply positive air only when the choke is open (to cater for the rare cases where boost is generated when the choke is out), or do they supply positive air all the time to somehow pressurise the float chamber to boost pressure? I think it is the former but not sure. The standard non-turbo carbs have a small gauze vent at these locations on the carb.

[Rolf]

Had the same happening. Found it also not downwards in the undertray, but more upwards. If I remember correctly it was laying near the alternator bracket. Car was nearly undriveable without it on the motorway at speeds above 60mph when boost needs to built up. Fuel starving is the problem I think. This banjos work for keeping the same fuel level in the carbs when under boost pressure.  Good luck with the search!

[molemot]

As the St. Tropez Owning One has said...you have to keep boost pressure on the top of the fuel in the float chamber, as well as increase the fuel pressure itself, so that the carburetter will function...it's a pressure carb for a reason, and it's these little pipes from the turbo supply to the plenum that provide the pressure. Nothing to do with the choke... Banjo bolts are readily available, don't forget the sealing washers...these are my "go-to" guys for car plumbing...http://www.thinkauto.com/

 

[Andyww]

50 minutes ago, molemot said:

As the St. Tropez Owning One has said...you have to keep boost pressure on the top of the fuel in the float chamber, as well as increase the fuel pressure itself, so that the carburetter will function...it's a pressure carb for a reason, and it's these little pipes from the turbo supply to the plenum that provide the pressure. Nothing to do with the choke... Banjo bolts are readily available, don't forget the sealing washers...these are my "go-to" guys for car plumbing...http://www.thinkauto.com/

 

This makes perfect sense and was the way I understood it to work.

The description in the parts book is "Banjo, Cold Start Air", and the hose: "Hose, cold start, banjo to diffuser" which is rather confusing as to its function.

The banjo bolts seem to be non-standard. Longer than normal but SJ have them.