Is it normal to have to pump the gas several times to get accelerator pump squirt ? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 11-16-2010, 01:41 AM
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Is it normal to have to pump the gas several times to get accelerator pump squirt ?

Hi, Im working on a 64 vw bus and I am installing new solex 35mm pdsit carbs. Engine drops out on take off then picks right up upon pressing gas pedal. Ive suspicious of the accelerator pumps. Already put in new diaphrams. Noticed that if I let the carbs sit for 10 minutes or slightly longer, they dont squirt till 1/8 to 1/4 throttle when throttle is opened slowly. Pump them several times then they squirt right off the bat. Im thinkin the check balls arent holding. I can also cruise, let off the gas, get back on the gas, engine drops out in same throttle range, then picks up when I go past drop out spot. Already blew out passages. Checked fuel pressure. I thought accelerator pumps were supposed to squirt no matter what. Thinkin about putting a very small spring behind one or both check balls to see if that helps. Not sure if theres one there now. Cannot find a parts breakdown of these carbs either. I figured since the hotrodders forum has tons of followers that use carbs, Id get the nitty gritty low down on accelerator pump operation.

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Old 11-16-2010, 02:40 AM
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You want an immediate pump shot.

What I have done in the past is to take an old check ball and lightly tap it against the seat, using a punch and a small mallet.

This "re-forms" the seat and will often cure a leaking check ball and seat. Just don't get too carried away hammering on it- you want to give it only as much of a hit that will allow the ball to form the seat, and not much more.

Mark the check ball w/a Sharpie to keep the check ball orientated the same- so you don't use the side of it that has been hit w/the punch against the seat. It probably will not 'dent' the ball, but just to be safe.
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Old 11-16-2010, 07:54 AM
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I'm not familiar with your carb but as with all, be sure to check for any slop in the accelerator pump linkage. The arm should move as soon as you step on the gas and if there isn't any adj. such as different arm holes to change the fulcrum point sometimes a slight bend on the link to the arm can be done to remove any gaps in the linkage. Good luck.

You might want to check the condition of the spring if any, under the diaphragm in the pump reservoir.
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Old 11-16-2010, 01:14 PM
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yep, its not the linkage, I can move the actual pump lever and no shot until.... the pump looks similiar to the holley style diaphram only perfectly square. Pump is on the side of the foat bowl. One check ball goes in vertically, the one in the foat bowl, Im not quite sure yet how to tap that one until I remove it. Spring under the diaphram is there and still sports the "yellow" plating on it. Not sure what to check as for height, or tension.

Last edited by fumplet; 11-16-2010 at 01:27 PM.
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