If your Stromberg 4A isn't squirting gas when you pump the throttle, you’re looking at a failure in the accelerator pump circuit.
1. The Pump Cup is Dried Out or Cracked
This is the #1 culprit, especially if the car has been sitting or you're using modern ethanol gas. The leather or rubber cup on the accelerator pump plunger can shrink or crack.
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The Test: With the engine off and the air cleaner removed, look down the primary (front) bores and pump the linkage. If you see the plunger moving but no fuel spraying, the cup isn't creating a seal against the pump well, or the passage is plugged.
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The Fix: You’ll need a new pump plunger (part of a rebuild kit). If it's a leather cup, sometimes a few drops of light oil can temporarily swell it back up, but a replacement is the only real fix.
2. Stuck or Missing Check Balls
The Stromberg 4A uses small steel check balls to control the direction of fuel flow.
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Inlet Check Ball: This lets fuel into the pump well from the bowl but closes when you push the pump down. If it's stuck open, the gas just squirts back into the fuel bowl instead of out the nozzles.
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Outlet Check Ball: This stays closed to keep fuel in the discharge passage. If it's stuck shut (usually from old gas "varnish"), no fuel can get out to the nozzles.
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The Fix: You’ll need to remove the air horn (top cover) and ensure the balls are free and the seats are clean.
3. Clogged Discharge Nozzles
The "shooter" nozzles that actually spray the gas into the venturi are very small and easily clogged by tiny flakes of rust or debris from the fuel tank.
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The Fix: Use a very thin copper wire or compressed air to blow out the discharge cluster. Be careful not to enlarge the holes.
4. Low Fuel Level in the Bowl
If your floats are set too low or the needle/seat is sticking, there might not be enough fuel in the accelerator pump well for it to grab a "sip" to spray.
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The Fix: Verify your float level. If the bowl is dry, you have a delivery issue (fuel pump, filter, or needle/seat).
5. Linkage Issues
Check the external rod that connects the throttle shaft to the accelerator pump lever.
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The Fix: Ensure the cotter pins are intact and the rod hasn't popped out of the hole. Sometimes there are multiple holes for "Summer" or "Winter" settings—make sure it's actually moving the pump arm through its full stroke.
A quick tip for your 4A: Since these have a pot metal body, if you take the top off to check the check balls, be very careful when re-torquing the screws so you don't warp the air horn.
