85 12a

wondering how the accelerator pump is supposed to work on the carb. I'm used to other carbs where actuating the pump (when there is fuel pressure) squirts fuel into the bores.

My carb doesn't do that. It does fill the main air bleed, but not enough to actually squirt into the bore.

Is this normal? The diaphram is not ruptured and the adjustement hasn't changed. If not normal, what should I be looking at to troubleshoot.

I'm familar with carbs, rebuilt a few holley 600s, and have a 750 double pumper on my tbird.

Thanks!
Scott

 

This is almost exactly what I was wanting to ask. Kinda weird.... Anyways, Carl or Sterling if you are out there - WHEN EXACTLY should the AP start to move? Should it be at the same time as the throttle just starts to open? I was thinking this could be a cause of my "low gear steady throttle bucking" that I am experiencing. Am I on the right track here? Anyone? Not to thread jack but it would hopefully help both of our problems, or at least give me some insight. Thanks, Ian

 

Yes Ian it should squirt as soon as the throttle moves. Youll get hesitation if it doesnt.

The fuel enters the well behind the AP housing from a drilled passage in the float bowl. On the top of the body in this location is a brass plug. Underneath it is a brass weight and a checkball. This keeps the fuel from going back into the bowl when the AP is actuated. The fuel would then travel thru a drilled passage to the center of the main body, passing thru another checkball and weight ( whos function is to trap fuel in the nozzle so theres no delay when the AP operates. If these were missing there would be an air pocket and youd have to wait for fuel to travel back up the passage before you got any squirt. Also in order to suck fuel from the bowl, this checkball must close so the pump can generate a low pressure and suck fuel from the bowl rather than sucking it back in from the nozzle area). which are located directly below the AP squirter nozzle, and then on thru the nozzle and into the carb barrels. Missing and/or stuck checkballs and weights will cause your AP to be inop. I see this on some of the carbs that come thru our shop. Probably lost accidentally during previous rebuilds by people who dont know what they are doing.