The 1974 Chevy truck has a mechanical fuel pump with a built in pressure regulator.
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It controls / regulates the fuel pressure.
That depends on what engine it has.
It is in the throttle body.
Engine oil pressure, cooling system pressure, ac pressure, fuel pressure?
The fuel pump is kaput.
Need engine size.
use a pressure guage hooked to the scrader port on the fuel line.
the oil failed and made something wrong
9 to 13 LBS. No more and no less.
In the low pressure service port, the smaller of the two.