On some WCD variants, instead of a loose check ball in the very bottom, Carter used a screw-in jet/valve assembly. It looks like a small threaded brass piece, often combined with a screen and a triangular retaining spring/clip. That unit performs the same function as the intake check ball: it allows fuel to enter the pump cylinder on the upstroke and prevents backflow when the pump is pressed.
1 - Check - Intake - usually the smaller ball in the kit.
2. Pump Lower Spring.
3. Pump Plunger Leather Seal - Some may be replaced with rubber.
4.Pump Upper Spring
5. Pump Plunger Assembly
6. Pump Jet
7. Pump Discharge Check Needle
Why It’s Different
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Early WCDs often used the check ball and retainer clip design in the pump well.
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Later WCDs (and some specific OEM applications) used a screw-in check valve/jet assembly. Carter built them that way intentionally — so you’re not missing parts.
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The triangular spring is the retainer that holds that assembly in place and ensures it seats properly.
How to Confirm It’s Working
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With the pump removed, fill the bowl with fuel.
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Watch the pump well — fuel should rise up through that valve into the bore.
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On the downstroke, it should seal tightly, forcing fuel toward the discharge passage instead of back into the bowl.
If it doesn’t seal, you may need to clean or replace the valve assembly, just as you would replace a check ball if worn or pitted.
