Why the Accelerator Pump Jets Keep Blocking
On Solex 44PAI carbs, the accelerator pump circuit is very sensitive to any debris — even microscopic particles — because the discharge nozzles have extremely fine orifices.
Common causes:
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Residual debris in the fuel system - Boats tend to sit around which causes the gas to turn into varnish.
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Even after an ultrasonic bath, if your tank, lines, or pump have varnish or corrosion particles, those particles will keep working their way into the carb and clogging the nozzles.
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Ethanol-blended fuels can loosen varnish and rust that were previously “stuck” in the system.
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Degraded fuel hose or pump diaphragms
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Old rubber hoses and mechanical fuel pump diaphragms can shed tiny black rubber particles that plug the pump jets quickly.
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Dried fuel residue inside the nozzles
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After running, if the car sits, evaporating fuel can leave a film of gum in the tiny bore of the nozzle, plugging it again in minutes.
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Faulty or missing inlet check valve in the accelerator pump circuit
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If the inlet check valve ball or weight isn’t sealing correctly, fuel can drain back or carry particles into the nozzle.
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Options & Fixes
Since new accelerator pump jets for the 44 PAI are nearly impossible to source, here’s the practical approach:
1. Deep clean AND polish the jets internally
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Use a single strand of fine copper wire (from electrical wire) to gently ream the orifice. Don’t enlarge it — just break varnish.
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Follow with multiple carb cleaner flushes and compressed air from both directions.
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Ultrasonic is good, but adding a mild solvent (like carb cleaner diluted with mineral spirits) often breaks varnish better than plain water.
2. Add a high-quality fuel filter before the carbs
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If you don’t already have one, fit a 10–20 micron filter between the pump and the carbs.
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If you have one, try a finer element — paper filters catch smaller particles than sintered bronze or mesh.
3. Flush the entire fuel system
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Drain and inspect the tank — look for rust, varnish, or black bits.
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Blow out the fuel lines or replace rubber hoses entirely.
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If you have a mechanical fuel pump, consider rebuilding it — old diaphragms are a debris source.
4. Inspect & clean the pump inlet check valves
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The Solex 44PAI has tiny inlet and outlet check valves in the accelerator pump circuit.
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If the inlet check isn’t sealing, backflow can carry sediment into the nozzle when the car sits.
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Remove the check ball/weight, clean the seat, and reassemble.
5. Use fresh non-ethanol fuel if possible
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Ethanol can loosen crud in old tanks and attracts moisture, which accelerates corrosion.
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If you can’t get ethanol-free, use a stabilizer and keep the tank full to reduce rust.
Key point:
If your jets are clogging again in minutes after being spotless, the real problem isn’t the jets themselves — it’s that contaminated fuel is still feeding them. Until the contamination source is removed, you’ll keep chasing your tail.
