blowing 15 amp main fuse under hood

A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well in most circuits, but this one needs to pass higher current, so you might want to use a head light bulb. A brake light will limit current to one amp. A head light bulb will pass up to five to six amps. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

I just now started working on looking for a short. I wired a sealed beam headlight to the 15 amp main fuse the light turns on if I remove the 30 amp injection square fuse the light goes out. The injection fuse is not blown . Could this mean a short in the injector wiring

This doesn't make sense. Please clarify, "I wired a sealed beam headlight to the 15 amp main fuse the light turns on if I remove the 30 amp injection square fuse the light goes out." Do you mean the test light turns on when you remove a fuse?