Weber Marine 4 Barrel Carburetor – Accelerator Pump Test


Weber Marine Accelerator Pump

 Weber Carburetor Main DischargeOne of the most common problems on almost any carburetor is when the accelerator pump circuit fails to deliver the correct amount of fuel. The accelerator circuit works, you guessed it, when accelerating. Throttling up requires an extra shot of fuel and the accelerator pump forces that extra fuel up through the main discharge and out the venturi, mixing with the fuel already being delivered to the engine.

(a) illustrates the main discharge hole. This hole will either have a ball and weight, or a ball and spring. Replace with the same combination. Check ball 1st, then either the spring, or the weight.

There are several things to think about when rebuilding your carburetor, especially around the accelerator pump circuit. Make sure the pump well is polished so that the pump cup glides smoothly and clean out all of the small passages in the venturi. Using thin wire is about the only way, since cleaners and compressed air are not going to remove all of the ethanol deposits left behind.

With everything clean and you are ready to assemble the carburetor, it is a good idea to test the accelerator pump circuit before closing up the carburetor.

Test your accelerator pump circuit as follows:

  • Fill the float bowl with liquid. We use mineral spirits.
  • The accelerator pump well should fill up with liquid.
  • Insert the pump and press down. Liquid should come out of the main discharge.
  • Replace the check ball.
  • Hold the check ball down with a brass drift punch (gently).
  • Again, press down on the pump. You should feel a slight resistance since the check ball is not allowing liquid up through the discharge hole. If no resistance, then gently tap the check ball and the drift punch in order to seat the check ball.
  • Install the venturi cluster and gasket.
  • Press down on the pump again. You should get a good squirt out of the venturi. If not, then the passages are plugged. Use thin wire to clean out the passages.

With the test above completed you can feel confident that the accelerator pump circuit is going to perform as it should.

International Shipping

We have a big following when it comes to people buying carburetor parts from other countries, but shipping to other countries can be a challenge both in time and cost.

As of today we are offering a new shipping option for those outside of the US called Bongo. Many will already know about this service, but for those who don’t, this gives you another option of how to ship your order. We look at this option as being between our normal 1st class international (USPS) and FedEx. On our side we are simply shipping to another US address, using the shipping option selected by you. Bongo takes care of the rest.

The most economical shipping method is to use our USPS 1st class international shipping, but it takes 20 days avg to get your order, depending on customs and we don’t offer this service to all countries. Avg price for 1st class international is around $15.00. FedEx depending on the method you select is much faster, usually about a week, but costs can be $60 or more. Using Bongo, depending on where it’s going can cost around $25.00. Bongo typically ships to anywhere in the world in 1-5 days (+ time from our warehouse to your US address). You can even track your order all the way to its destination.

Bongo International provides our customers with their very own US address. Once you have a US address, you will be able to make purchases with us as well as other US based online retailers. Bongo receives your purchases and logs them into their online system which you can use to view your items and consolidate them with multiple orders.

International customers can save up to 82% off typical international shipping rates by following these four easy steps:

Register with Bongo and receive a U.S. shipping address.
Enter the Bongo address as both your billing and shipping address.
Use the credit card that you have on file with Bongo as the payment method.
Once the order arrives at Bongo, log into your account to forward to your country.

For more information about the Bongo service, or to get an estimate of what the shipping costs are visit Bongo International

Carter B&B Carburetor Lacks Power From Idle To Cruise

Carter B&BI would look closely at the main discharge. See #28 on the diagram to the right. Remove the aluminum clean out plug. If you purchased our kit you will find one was added but bagged separate from the kit.

Using  a flat blade screw driver remove the discharge jet. These are often frozen into the carburetor. In these cases I would leave it in the carburetor and clean it out while in the carburetor. You may have to use thin wire to get the jet cleaned out. I know one person that drills the jet out by 1 size to accomidate the current fuel, but personally I would do that only if you are having an issue when accelerating. These jets are not available so damaging one is not an option here.

Make sure the passage going from the main discharge to the accelerator pump well is not clogged and clean.

# 30 is the pump check ball. Make sure it wasn’t left out and is clean. This is the bigger check ball of the 2.

On most B&B carburetors there will be a check ball at the bottom of the pump well along with a clip that holds it in. This is where the fuel enters the well. Make sure the ball is there and that it is working. When you fill the float bowl with (mineral spirits), the ball should lift up by the weight of the fuel and fill the well.

Put the main discharge back in along with the pump check ball and plug, then fill the pump well with fluid. Insert the accelerator pump and press down. Fluid should come out of the main discharge and into the carburetor throat. It’s difficult to describe just how much should come out, but you will see it drip out the bottom of the carburetor in a good quantity.