Mazda Repair: Miata fuel pump fuse problem, fuel pump relay, jumper wire

Question
Hi! I have a 1993 Mazda Miata that continues to blow fuel pump fuses. After replacing the fuse it will run fine idling in the driveway but as soon as you drive about a mile the fuse will blow. The car has about 120,000 miles so I thought it was about time for a new fuel pump anyway so I replaced it. No change. It still is blowing the fuse. I checked the wiring as much as I can and don't find a short. I guess what baffles me is that usually a short will blow a fuse quickly. Im thinking about running a fused wire directly from the pump to the battery to eliminate a few possibilities. A friend said a clogged fuel filter will cause the pump to over work. Not sold on that idea but needs changed anyway. To say the least I need an expert here. I'm glad you have Miata experience! I have two of the little fellers.   Cliff

Answer
The likelihood of a wire harness short is slim.  the Miata is well built.  Unless the car has been in a collision at some point in time.

The fuel pump relay is most likely your fault.  If it is shorting internally overheating this could cause the relay to fail and thus no power to the pump.  Avoid doing and wire bypass steps, save that as a last possible resort this problem should be fixable.

The relay is under the dash drivers side if you have trouble locating it place a jumper wire between GND and F/P in the Diagnostics box, drivers fender under hood.  Each time you contact this jumper the relay will click.  Before condemning it look to see if the harness and plug at the relay is in good shape.