acco fuel overflow

hello all,
back from a couple of weeks touring FNQ so missed the big 200... I saw no rusty trucks waiting for love up there, but did see a twin steer bogie drive Leader near Cairns still working hard.

Cranked the ACCO up today for some therapy, to find fuel dripping from the fuel canister that supplies the preheater.

For the uninitiated, the excess fuel along the injector lines runs to the canister where magic supplies a drip or two to the heater element in the intake mainifold for starting, the rest should just run back to the tank (and some does).

I put the compressor over the lines etc all seem fine, but after a minute of idling the fuel starts to rise up through the breather in the top of the canister. Why is it so.... and I just realised I dont know what causes the fuel to go where and when it does for starting???

The book says full throttle for starting proceedure so is it vacum or is there an electric switch connected to the heater element.

I have a parts catalogue but there were no clues there this time.

Your help would be much apprecitated.

Sarge :-X :-[

Sarge,
The bit in the manifold where the fuel line goes to and the electrical connection has a thermo valve in it. When pre heating the coil starts to glow and heats the thermovalve up. It expands and lets the valve of its seat and dribbles fuel on the coil which catch's fire and create some heated air in the inlet manifold. The little pot in the return line fills up to outlet pipe height then runs to the tank. This is done so there is always fuel in the pot for a start. If there is any restriction between the pot and the tank it will spew out the top.
Good old pomms, they thought of everything.
Barry

thanks Barry,
I blew the compressor down the return line and made my square tank round, but might need to check that the line is not pinched, because it is still coming out the top. Is there a valve or float in the canister..... I have to pull the dash out to get the fuel canister off the wall if I want to have a look.

sarge :-X

Sarge,
I had a look in the canister on my loader engine and there isnt anything inside it. I emptied it then run the engine with the top off and it fills up slowly to the overflow fitting back to the main tank and thats it. Maybe yours is a different model ??...You said when you blew air through the pipe the tank changed shape. It shouldnt have. Have a look and make sure your tank vent isnt blocked. Its what could be causing your problem. Take the fill cap off the main tank and give it a run and see what happens. The return fuel side of the system isnt pumped so it doesnt take much of a restriction to back up.
Barry