Engine will not rotate. Fuse blows every time.

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My #8 (ign fuel starter) fuse blows every time I try to start my vehicle. I've replaced the alternator, battery, relay switch and brought the starter in to get checked (3 times) and it was just fine. When I try to start the engine it doesn't rotate and the brake light comes on. The cables from the battery to the post are good no corroded wires or exposed wires that I can see. I cannot figure out what the problem is if any one has an idea of what the problem is it would definitely help.
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Tuesday, October 8th, 2013 AT 6:17 PM

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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. 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.

Fuse 8 feeds the starter relay, fuel pump relay, and three circuits on the ignition switch. If the test light gets bright as soon as you turn on the ignition switch, those are the circuits to check. If the short is related to the starter relay circuit, if the short is before it, the fuse will blow right away when you replace it. If the short is after the relay, the test light will not get bright until you try to crank the engine. Remove the starter relay, then the starter, of course, won't work, but the fuse won't blow again.

If the test light gets bright for just one second after turning on the ignition switch, then gets dim or goes out, that is caused by a short after the fuel pump relay. Pull that relay out and pop a new fuse in. It won't blow, and the starter will work, but of course the engine won't run with no fuel pressure. It's very rare for fuel pump motors to short. More likely the wire running back to the fuel tank is grounded or pinched somewhere.
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Tuesday, October 8th, 2013 AT 11:05 PM

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