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Holley 847, 897 Carburetor Troubleshooting

Is Your 847 Flooding on Start Up?

The Holley 847 choke plate has a poppet valve. The purpose of this valve is to open on start up so that the air isn’t choked completely causing a too much fuel condition. Make sure the poppet valve is not sticking. Remember that only vacuum is used to open this valve.

What if the Poppet Valve is Missing From the Choke Valve?

Just the opposite from above. With the valve missing, there may be too much air entering the carburetor in a cold engine condition thus starving the engine of necessary fuel. If you have a “hard to keep running when cold condition” check out the choke valve and poppet valve. When cold the poppet valve will be closed.


Flooding

Gas is running out of the top, or you get a strong gas smell? This is a sign of flooding. What is flooding? Simply, there is too much gas getting into the float bowl.

Here is a list of items to check when this happens:

  • Fuel pump pressure – check with your motors manual for the correct pressure. New pumps are especially suspect.
  • Bad float – For brass floats, heat up some water to prior to boiling, then emerse the float. There should be no bubbles.
  • Check float level
  • Make sure float isn’t binding – move it up and down by hand and see if you feel anything catching.
  • Make sure float doesn’t rubbing somewhere.
  • Does the seat have a gasket?
  • Did all of the old gasket get removed?
  • Look for any cracks around the area the seat screws in.
  • Maybe the viton tip on the needle is damaged. There should be no pressure put on the needle when adjusting the float.

Is your 847 flooding on start up?

The Holley 847 choke plate has a poppet valve. The purpose of this valve is to open on start up so that the air isn’t choked completely causing a too much fuel condition. Make sure the poppet valve is not sticking. Remember that only vacuum is used to open this valve.

What if the Poppet Valve is Missing From the Choke Valve?

Just the opposite from above. With the valve missing, there may be too much air entering the carburetor in a cold engine condition thus starving the engine of necessary fuel. If you have a “hard to keep running when cold condition” check out the choke valve and poppet valve. When cold the poppet valve will be closed.

Why is Fuel Leaking Out of the Throttle Shaft

Fuel coming out of the throttle shaft indicates too much gas getting into the bore. Raw fuel runs down the bore and out the 1st place it can which is the throttle shaft.

A worn throttle shaft will lean vacuum, not fuel.

One possibility is heat soak. This will usually happen on a hot engine. Engine is turned off and the fuel inside the flow bowl boils out into the bore.

One thing to look for is richness. Is the tailpipe throwing out black smoke? Are the spark plugs burning black? These would indicate too much gas is coming from the flow bowl.

  • Test the needle & seat for leaks.
  • Check the float level.
  • Test the float for any leaks by heating up water just prior to boiling and immerse the brass float. Any bubbles indicate a leaky float.
  • Move the float up and down by hand to feel anything catching.
  • Inspect the float pin for wear.
  • Test the fuel pump for proper pressure. Check your motors manual but should be around 4 lbs.

Accelerator Pump

No spring is used below the accelerator pump.


Main Discharge Check Weight is Missing
No check weight available, but you can use most anything in it’s place. A 2nd check ball, or a piece of welding rod. Just be sure that there is room for the check ball & weight to move up when it need to. 1/8″ or so would be fine.
Updated on 10/17/2021

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