cigroller has a good thought, but there may be an easier way to monitor this if you are inclined to do some real simple wiring. If you can patch in a wire where he wants you to test for 12 volts, run that to the front seat, attach to a a test light or even just a bulb, then run to a good ground, you’ll be able to see at a glance when you have 12 volts reaching the pump, and when you don’t. This might be a bit less hassle… or not. If you get real adventurous, you could even tap into 12 volts somewhere and be ready to connect that to your test rig, and if the test light shows no power reaching the pump, then just connect your 12 volt jumper and see if that starts the pump. Best to put an inline fuse in your jumper line. I had a case once where my problem was in the circuitry, not the pump, on an older vehicle. Our solution, given the age of the vehicle, was to just abandon the factory wiring and deliver electricity on a new line. That Nissan truck ran several more years before dying just shy of 400,000 miles. Sad to see it go…