1. Home
  2. Knowledge Base
  3. Holley
  4. Holley 1920
  5. Holley 1920 1 Barrel Troubleshooting

Holley 1920 1 Barrel Troubleshooting

Mike's Carburetor Manuals

Which Springs Go On The Diaphragm?

I have a 1920 Holley that has the accelerator pump with THE FLAT notched bar connected to the diaphragm (instead of the ROUND bar and the smaller spring).
My question is this; I know the round bar type has a spring on both side of the diaphragm, but is the FLAT BAR type suppose to have a spring on BOTH SIDES of the diaphragm.

The flat stem pump uses a spring between the pump diaphragm and the economizer body (some call this the metering block).

Check out our 1920 kits

What might cause my carburetor to flood?

  • Fuel pump pressure too high – test and compare with your motors manual. New pumps are especially suspect. Check your motors manual for the correct pressure, otherwise look for 4.0 to  4.5 lbs.
  • Test needle & seat – you can try to blow into the inlet to see if you can dislodge anything that might be holding the needle up. You may have damaged the needle when installing, or adjusting the float. Any pressure on the needle can cause the viton tip to score.
  • Did you clean all the gasket material from under the seat.
  • Brass float – shake to see if leaking, or heat up water just prior to boiling and immerse the float. Any bubbles indicate a leak.
  • Nitrophyl float – The only way to check this is the weigh it in grams. There are 2 different floats. One weighs 7.5 grams, the other 12.5 grams.
  • Move float up and down to see if it is catching, or rubbing.
  • Economizer diaphragm may be bad, or the vacuum passage is plugged. At idle vacuum pulls the diaphragm up. At higher speeds the diaphragm goes down and pushed down on the power valve. Make sure the power valve isn’t sticking.

Hard Starting

  • You first need to eliminate the ignition system. The distributor advance can cause hesitation.
  • Take the air cleaner off, turn the engine off and look down the carburetor.
  • Pump the gas once. You should see gas coming out of the main discharge, into the carburetor bore. If not, then the accelerator pump is bad, or a passage is plugged.
  • Is there gas coming out of the back of the pump area where the round, or flat shaft comes out. If so, then the accelerator pump diaphragm is bad.
Updated on 04/26/2021

Was this article helpful?

Related Articles

Need Support?
Can't find the answer you're looking for?
Contact Support