Mech Fuel Pump Spacer 2A vs 3A

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   What was the reason 3A's specified the 1/8" spacer between the fuel pump and the block, and the 2A's didn't? Even with the non-vacuum metal or glass bowl type. Was the difference in the pump diaphragm (volume pumped), the cam lobe (I don't think so), or at the carb?

I'm replacing the pump on my 3A (cracked housing), and there was no spacer. None of my parts trucks have spacers either, one being a 2, and one is a 3. And looking into all 3, I don't see/feel any cam lobe wear. 

Is there really that much difference between two mechanical pumps output that the volume varies that much to warrant spacers?

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Kendog Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 19 Jan. 2010 Location: Western NY Status: Offline Points: 122	Post Options Post Reply Quote Kendog Report Post Thanks(0) Quote Reply Topic: Mech Fuel Pump Spacer 2A vs 3A Posted: 30 July 2012 at 12:47pm
	What was the reason 3A's specified the 1/8" spacer between the fuel pump and the block, and the 2A's didn't? Even with the non-vacuum metal or glass bowl type. Was the difference in the pump diaphragm (volume pumped), the cam lobe (I don't think so), or at the carb? I'm replacing the pump on my 3A (cracked housing), and there was no spacer. None of my parts trucks have spacers either, one being a 2, and one is a 3. And looking into all 3, I don't see/feel any cam lobe wear. Is there really that much difference between two mechanical pumps output that the volume varies that much to warrant spacers?

rocketeer Members Profile Send Private Message Find Members Posts Add to Buddy List Member Sponsor Member Joined: 26 June 2008 Location: Lehighton, PA Status: Offline Points: 3473	Post Options Post Reply Quote rocketeer Report Post Thanks(0) Quote Reply Posted: 30 July 2012 at 3:43pm
	The spacer is specific to the dual action pump which became standard on CJ3A's. The pump did not provide sufficient clearance due to size so the arm was changed and a spacer added to compensate. If you are installing a single action pump on any of the L-134's the spacer is not used. If you use a spacer with an SA pump it might not pump at all or at best put out too little fuel pressure. Conversely if the spacer is left out of a DA pump it will produce too much fuel pressure with the result that the carb will likely run rich and/or flood and after-boil. Larry Edited by rocketeer - 30 July 2012 at 3:48pm

Kendog Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 19 Jan. 2010 Location: Western NY Status: Offline Points: 122	Post Options Post Reply Quote Kendog Report Post Thanks(0) Quote Reply Posted: 30 July 2012 at 4:15pm
	Thanks Larry. So the dual action pumps are the 'with vacuum' style? My cracked pump and the replacement (Walcks) glass bowl type are w/o vacuum. So no spacer advised on the new (unworn) replacement, correct?

scoutpilot Members Profile Send Private Message Find Members Posts Add to Buddy List Member Joined: 30 Dec. 2008 Location: Asheboro, NC Status: Offline Points: 4373	Post Options Post Reply Quote scoutpilot Report Post Thanks(0) Quote Reply Posted: 30 July 2012 at 4:50pm
	You got it!