I turn my pump on at my remote and it takes 15 seconds for it to starrt pumping. It doesn't happen every time but has happened half of the time in the last 2 days. Any suggestions

Poor connection on an angle plug maybe????

concrete volume control on the minimum?

Could also depend on what year it is. Some of the pre 2000 models would take a about 30 seconds or so once you energize the remote box. Its going threw all the functions. Open your computer box when your about to energize your remote and see what the lights to your fuses are doing. If they light up all together then everything should be fine. If not start checking your connections.

Check your connections.  Could be a ground problem.  Weather getting colder and damp.

Most likely it is some corrosion in the angle plug connection to the solenoid or pneumatic valve solenoid depending on which type of pump you have. Try wriggling the connector when the problem occurs.