[ossiblue]

Let's not confuse the issue. You have a 79 SC. The fuel pump is not supposed to run with the key in the "on" position. Period.

CIS cars from 73-75 did not have the pump relay nor the air flow sensor switch so the pump will run on those year cars with the key "on." Yours should not.

With that in mind, go ahead an begin your troubleshooting. You should first establish that your power to the pump, via the relay, is correct. Secondly, you should establish that the relay is transferring that power to the pump. Third, you need to confirm that the pump runs as soon as power is applied, every single time--either by removing the relay and jumping socket 30 and 87a and turning on the key, or by unplugging the air flow sensor and turning on the key, or by lifting the plunger. It's your decision on how you want to test the reliability of the pump turning on.

If all the above is done and checks out, then you will need to test flow and volume of the pump and a gauge set will be necessary.