Hi,

I have a standard set up 340 with AED all plugged in as designed. I can find most answers to things from the workshop manual or on line but I can’t find this anywhere so I’m stumped.

My question is should all three wells on the AED fill to the float level of fuel? I’m assuming in operation the fuel in the well is an initial dump of fuel to get it started and then subsequently air is pulled in by all three wells until the AED switches off via the otter switch at 35 degrees.

Currently only my middle well has fuel in, the other two are bone dry. In fact they had a lot of dry guff in them which I blew out with a compressor. I can find a hole in the middle well easily where I’m assuming the fuel enters, but for the life of me I cannot find a hole on the two outer wells to see if the hole is blocked to clean it out. Are the outer wells just for air or decoration?

The picture (hopefully) attached tends to suggest that all three wells should be at the level of the float in the carb and there should be a hole right at the bottom of the well.

My other question simply for curiosity is the triangular bit of metal that covers the wells is triangular and only fully covers the central well and only partly covers the two outer wells, why is that? Anybody know? Why not cover all three to stop dirt ingress which mine clearly had.

Thanks all

 

Hi, first I should mention that this device is usually referred to as a 'starting carburetor' - AED is something different on newer carbs. They also call 'em 'hissers' because of the sound they make. No big deal just that if you post about AED's it may not get you an answer because they're different.

But to answer your question you'll only see fuel in the middle drilling. The device actually functions like another carburetor when the solenoid is activated exposing it to manifold vacuum.

You're right about the reason fuel level is high when the engine is off. The column of fuel above the starting carb's jet (even with the main carb level) is additional enrichment for cold starting. Once it starts the needle is sucked down into the jet and it's in carb mode.

The little triangle cover not only keeps crap out, it also is there to shield everything from a fuel bath if it spits back - which it can do. Some applications even have a much larger umbrella cover over the whole thing as well.

A common failure mode for these things is rust or dirt clogging the area under the jet or the tiny passage to the carb bowl that feeds it. Usually happens when a car sits. Doesn't seem like you have that problem since you definitely have fuel in you starting carb.

~Mike
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[QUOTE=rustfreemike;2205625]Hi, first I should mention that this device is usually referred to as a 'starting carburetor' - AED is something different on newer carbs. They also call 'em 'hissers' because of the sound they make. No big deal just that if you post about AED's it may not get you an answer because they're different.

But to answer your question you'll only see fuel in the middle drilling. The device actually functions like another carburetor when the solenoid is activated exposing it to manifold vacuum.

You're right about the reason fuel level is high when the engine is off. The column of fuel above the starting carb's jet (even with the main carb level) is additional enrichment for cold starting. Once it starts the needle is sucked down into the jet and it's in carb mode.

The little triangle cover not only keeps crap out, it also is there to shield everything from a fuel bath if it spits back - which it can do. Some applications even have a much larger umbrella cover over the whole thing as well.

A common failure mode for these things is rust or dirt clogging the area under the jet or the tiny passage to the carb bowl that feeds it. Usually happens when a car sits. Doesn't seem like you have that problem since you definitely have fuel in you starting carb.

~Mike
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Thanks Mike

So are the outer two drilling’s used for air only and so have a hole there somewhere? Or are they just hollow drilling’s with no function?

I can’t seem to get the revs up when the starting carb is in use, which makes me wonder if it is getting more fuel but not enough air to raise the revs. If the outer two drilling’s are used for air maybe blasting them out has cleaned them out and will now allow more air in.

Thanks

 

On the ones that I have those outer passages go all the way down and stop. I have also wondered about them. I've spent time poking around at the bottom of those 2 with a thin 'L' shaped wire and cannot find a passage. Also on the outside of the array of 3 passages there are drilling bosses (cylindrical nubs) to allow positioning of machining tools to complete a cross drilling of some kind. The only one that's been obviously drilled and filled on mine is the center one that leads to the jet and needle. Also if you fill an outer tube with brake cleaner it just sits there. So, at least on part no.AUC 2755 version if it, they don't seem to lead anywhere unless there is an extremely tiny orifice at the bottom that doesn't leak under surface tension but does under vacuum. Also sometimes it seems like the outer ones are full of fuel because it spits back and fills em up and then the fuel just sits there.

It is entirely possible that there are other cars where those outer tubes are used which is probably why they're there with all the drill bosses.

As for your revving problem, even though it seems like the jet area is at least partially open you might have an issue with a ton of crap under there - I've seen them where the center column fills but there is still a ton of gunk under the jet... Hard to say. Would probably not hurt to take it apart and clean it really well.

There is an adjustment of the starting carb needle as well as the fact that the regular carbs need to be set up properly for it to work correctly too.

~Mike