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Zenith-1 venting issue

Oregon Desert model 45

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After my Model A sat for several years, I got the motor running but just barely.  It would run for about 5 seconds then die.  I disassembled the carburetor,  poked a wire thru all the jets, blew air thru  it, and soaked the float valve in acetone overnight, it still was not working.  To rule out the tank shut off valve and sediment bowl as potential culprits, these too were disassembled and blown out. With everything freshly cleaned out, I turned the on shutoff valve and no fuel entered the sediment bowl until I loosened the carburetor strainer end cap. This means the carb is not venting air to allow fuel to enter the sediment bowl and in turn into the carb.  There is a vent passage in the carb upper casting, red arrows below, which is clean.  The float valve is a replacement ball type, which moves freely without sticking, and I can hear it rattle when the carb is assembled, so it should be working. Any ideas to solve this ?  I put a spare Tillotson carb on it and got it running pretty well.




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I am assuming since it runs OK on the Tillitson, the hole in the vent cap is OK, but it is always good idea to double check and make sure it is clear.


I have found that it sometimes helps to " bleed" the Zenith carburetor after it has been taken off and re-installed.


Connect the carburetor, fuel line, etc. Turn the gas "on" at the shut off. On the bottom of the Zenith there are two hex nuts. The smaller one is a drain. Remove the drain and theoretically, lots gas should flow out at a good speed. Let it run out for a few seconds and replace the drain while it is still coming out. After the drain is replaced, you shouldn't have any gas leaking out of the carburetor which will tell you the needle and seat have closed, and it should also fill the bowl with gas. The car should start and run fine if everything else is OK. 


Good luck and enjoy your roadster.

Edited by motoringicons (see edit history)
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