Holley 4000 Accelerator Pump Troubleshooting

Watch the nozzles at idle and also at a constant higher RPM. Remember that any pumping of the gas will push gas through the nozzles. Any leaking, or dribbling is a problem.

Make sure the pump discharge needle is in place and holding. To test, fill the bowl with fluid (mineral spirits) and while holding the needle down gently pump the accelerator. Fuel should not leak around the needle. If it does, inspect the needle for damage. Seat the needle by hitting it gently with a brass drift punch.

Make sure all vent holes are open.

The Holley 4000, also known as the "Teapot," is a classic four-barrel carburetor that was primarily used on Ford vehicles from the 1950s. Adjusting the accelerator pump stroke can be essential for ensuring smooth acceleration and preventing engine stumbles.

Here's a general guide to adjusting the pump stroke on a Holley 4000:

Materials Needed:

• Screwdriver set
• Wrench set

Procedure:

1. Safety First: Before starting, make sure the engine is off, the vehicle is in 'park' or 'neutral' with the parking brake applied.

2. Locate the Accelerator Pump: This should be on the lower side of the carburetor. On the side of the pump, you'll find a linkage with multiple holes in it. This linkage controls the pump stroke.

3. Check the Current Setting: Before making adjustments, see which hole the linkage is currently set in. This gives you a reference point.

4. Adjust the Pump Stroke:

   • Shorter Stroke: Move the linkage to a hole further away from the carburetor. This shortens the stroke and decreases the amount of fuel shot into the intake during acceleration.
   • Longer Stroke: Move the linkage to a hole closer to the carburetor. This lengthens the stroke, increasing the amount of fuel.

5. Re-Test: After adjusting, start the vehicle and check the acceleration. If it stumbles or hesitates, further adjustments might be necessary.

6. Fine-Tuning: If after adjusting the pump stroke, you still face issues, you might need to look into changing the pump cam or the pump nozzle (squirters) for a more significant change in fuel delivery during acceleration.

7. Re-tighten and Secure: Once satisfied with the adjustment, ensure all screws and fastenings are tightened, and there are no loose parts.

Remember, when adjusting carburetors, small incremental changes are often best. Adjust, test, and adjust again as necessary. If you're not familiar with carburetors or don't feel comfortable making these adjustments, consulting with a mechanic or expert on classic carburetors can be beneficial.