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Holley 1904 Accelerator Problem
Hi Mike, I resolved the problem I sent you last week. The problem was a vacuum leak at the base of the carburetor. Replaced the gasket and seems to be ok now. The other problem I am having is when I first start to accelerate the engine hesitates and I have to back off the throttle and pump the accelerator. Once I get going all is ok. I have adjusted the air fuel mixture but the problem remains. Do you think I should install a larger jet to increase fuel flow to match the air intake? If I increase throttle real slow it doesn't hesitate. Leads me to think too much air and not enough fuel.. Thoughts???

Installing a larger jet is not the answer. Do the steps below and you will probably find the problem.
  • Check the accelerator pump circuit action by looking down the carburetor (engine off) and pump the throttle. You should see a strong stream coming out of the main discharge nozzle. If it looks ok, then you have eliminated the accelerator pump as the problem.
No strong stream?
  • Make sure the main discharge nozzle is clear. Run thin wire through the discharge hole.
  • Check to make sure there is a gasket under the nozzle and it isn't broken. You don't want fuel bypassing the nozzle.
  • Make sure the accelerator pump diaphragm was put together properly. The pump, the return spring, then the economizer body.
  • While you have the diaphragm out, look at the carefully to make sure there isn't a crack, or tear.
  • The pump stem should have the spring over the stem, then the pump rod sleeve. The check ball should be installed in the small hole. If the spring is missing, or there isn't enough tension, then the diaphragm won't get the correct action, filling with fuel when needed.
  • The metering block, or economizer body can get warped over time. Be sure to grind the surface flat, or run a flat file over the surface to make sure it is flat. When they aren't flat, fuel can leak past the block.
  • The economizer body should have a check ball and a check weight on top of the ball in the economizer body, longer hole. The smaller hole will have the bigger check ball installed.
  • Did you clean the economizer body (metering block). Perhaps there is corrosion inside the holes which might mean the check balls are not sealing.
Good stream?
  • Assuming your distributor vacuum advance connects to the carburetor, you will need to make sure the vacuum isn't blocked. Remove the fitting and check for vacuum. No vacuum means the passage way is blocked, or plugged with something. It was a practice with some rebuilders to put a check ball in the passage way to block the vacuum when the port wasn't needed. Check the bottom of the main body to see if a check ball was put in the hole. Make sure the flange gasket isn't blocking the vacuum hole on the bottom of the throttle body.

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