Hard starting B2600i

I Have a 1989 B2600i 4x4. If it sits more than a day, it takes about 30 seconds of cranking and pumping the gas pedal and then it starts and runs and idles great. Turn it off and let it sit for 30 minutes and it starts right up again. Any suggestions? Fuel pump relay?

could be a leaky line, air might be getting in it, im not sure if the trucks have a check valve but if it does it could be bad, fuel filter might not be good.
have you checked or replaced anything on it?

I wanted to avoid spending money or random replacement right now, trying to find the most likely culprit first.