The “ Service Manual for Jeep Utility Vehicles” (Para C-18) states to test the Vacuum pressure to determine certain valve issues. 550 rpm with a goal of 18-21 in of mercury.

Checking the vacuum can tell you a lot about the status of the Valves.

OK, but this vehicles vacuum is generated by the mechanical Fuel Pump and not from the manifold. There doesn’t appear to be any manifold vacuum tap to check it with. E.g. the Carburetor vacuum line comes from the mechanical fuel pump. Not anything relating to the valves.

So how do I test the the manifold pressure? What am I missing?


1958 Willys PU L6-226 VIN 55268-45757