How to Troubleshoot an Edelbrock Carburetor
The Edelbrock carburetor is a square-bore design with a single accelerator pump, two main metering rods, vacuum secondaries, electric or manual choke, fast idle cam, singular float bowl and two idle mixture screws. In many ways, the design is similar to a Carter AFB. Multiple main jets are available to re-jet the carburetor to accommodate various compression ratios and engine displacements. These carburetors should always have a heat dissipating thermo-block under the carburetor sandwiched between two gaskets. The block keeps the heat away from the carburetor and keeps the fuel cooler.
Other People Are Reading
Things You'll Need
- Small common screwdriver
- Phillips screwdriver
- 3/8-inch drive spark plug socket
- 3/8-inch drive ratchet
Instructions
-
-
1
Test the choke with the engine cold. Remove the air cleaner. Use a finger to open the throttle by pushing the throttle lever about half way open and then release the lever. Check the choke to see if it is completely closed. If not, the choke is not adjusted properly causing a hard start.
-
2
Start the engine without further touching the accelerator pedal. The engine should be on the fast idle cam and the rpm should be close to 1500. If the rpm is too high or low, the cam is malfunctioning and needs to be repaired or adjusted.
-
-
3
Check to make sure the choke pull-down is functioning properly. Now that the engine has just been started, the choke should be slightly open from its fully closed position. If the engine is running too rich and the choke is fully closed at this point, the choke pull-down is defective and has a leak in the diaphragm. If the choke failed to close when the throttle lever was opened, the choke is either out of adjustment or the spring is defective within the choke housing. Loosen the three screws on the housing and turn the housing to close the choke. If the choke fails to move, the spring is bad.
-
4
Check for flooding due to a too-high fuel level in the float bowl. Allow the engine to run until the choke opens all the way and then look down the inside the carburetor primary chamber. Look for fuel dripping from the main metering holes, indicating too high a fuel level. The carburetor top cover needs to be removed, and the float adjusted and the needle and seat should be replaced.
-
5
Check the operation of the accelerator pump by observing the two projecting nozzles in the primary side of the carburetor. Open the throttle by hand quickly about a third of the way and release. Every time the throttle is opened there should be a steady stream of fuel from both nozzles. If no fuel or very little fuel is observed, the accelerator pump diaphragm is bad and needs to be replaced.
-
6
Check the secondary operation by observing the top throttle plates to see if they open when the throttle lever is snapped open and released. An Edelbrock carburetor has two sets of plates on the secondaries. The bottom set open mechanically while the upper set open through a vacuum. If the top plates fail to open when the throttle is snapped open and closed, there is a vacuum leak or a bad diaphragm in the carburetor. This situation would cause a lack of power under acceleration and a dead spot when the throttle is suddenly open.
-
7
Check the idle mixture for the proper setting. Turn the screws one at a time in clockwise until the rpm begins to drop. Turn the screw out counterclockwise until the highest rpm is reached and further movement of the screw makes no difference in the rpm. Now turn the screw back in clockwise until the rpm just starts to drop and at that point open it one-quarter turn. Do the same for the other screw and then repeat the process for both sides.
-
8
Check a couple of the easiest-to-get-at spark plugs for color indicating the fuel mixture at the main jets. Let the engine cool and pull the plugs. A plug with a slightly gray, clean look to it shows good mixture. If it is black the mixture is too rich and a step smaller main jet is needed as long as everything else was fine. If the plug is white and blistering the mixture is too lean. This requires one step larger main metering jet. Remember when checking mixture by plug coloration, everything else must be perfect.
-
1
