How to rebuild a Rochester Quadrajet 4MV carburetor

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 ====Trouble spots====
 Please keep an eye on the following areas during dis-assembly and rebuild.
+=====Accelerator pump assembly=====
+If the accelerator pump wasn't working correctly, be sure to attach the linkage to the pump arm hole nearest the pivot to get the biggest pump shot. You can try the smaller shot and if that works well, use it.
+There are several different accelerator pump rod lengths used depending on the carb, if it's the wrong length this can cause the pump to work poorly.
+If the springs are reversed on the shaft, that can cause it to work poorly. If the piston seal is wrong it can have a hard time pushing fuel and/or allowing the pump to refill.
+There's a ball that acts as a check valve under a screw in the float bowl, driver side. Be sure the ball is in place and sealing as it should. The check ball seat can be re-formed by carefully tapping an old check ball against the seat using a small punch and light mallet/hammer.
+Sometimes the accelerator pump bore gets glazed where it doesn't seal against the piston very well. The bore can be lightly honed using 600 grit wet or dry. I use a wooden dowel w/a piece of cloth wrapped around the dowel and the emery paper wrapped around the cloth. Then make like a boy scout starting a fire or like you're lapping a valve. You don't want to remove the finish, just break the glaze ever so lightly and to smooth the bore.
 =====Stripped or loose/damaged fuel inlet threads=====

Revision as of 19:12, 14 January 2013