Rebuilt a combination vacuum pump/glass bowl fuel pump om my 1949 Chevrolet 3100 series 1/2 ton pickup with a 216 cu. in. 6 cyl. to assist with the vacuum wipers. Cycled the pump 5-6 times as per the Chevrolet truck shop manual before tightening the vacuum side of the pump. The pump I removed from the truck was a single stage pump that the plunger could be cycled with very light thumb pressure. The combination pump after fully assembled would only cycle if I pressed the plunger/lever to the top of my work bench. My question: Is it normal for the combination pump to be much harder to cycle than a single stage fuel pump, or is the single stahe pump I removed just very weak?
