Only difference I can think of would be volume of vacuum available to the system? Does the small one have a port for the vacuum sensor idiot light sending unit thingy?
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Maybe the earlier vacuum pumps didn't draw as hard and required a larger volume to compensate for the lower vacuum?
Is it just a simple pipe connecting Pump-Tank-Servo with no valves?
Ahh right, thanks! My electric pump and tank just arrived so great timingYes, the pump should have a built in valve that senses how much vacuum is in the tank. When there is enough it stops making vacuum.
Diesels don't make a lot of vacuum in the manifold , this is why they have the vacuum pump . Its also why your brakes are very hard. So, block it off.