Quote:
Originally Posted by JmcEx2fifty
What should the vacuum be at
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Depends upon the petcock. Typically they flow between 5-10inHg. But I’ve seen failing ones or ones with leaking diaphragms take 15-20inHG. And some doesn’t flow all no matter how much you apply.
Also good test is looking at gauge to see if diaphragm holds set vacuum level. That is, it doesn’t drop and you don’t have to keep on pumping to keep petrol flowing.