93 mmax cranks but won't start.

Hello everyone. I'm new to this site and I've got a problem with my 93 mighty max 4g64. It died on me on the way to work right after I filled up with gas. I got it home and started looking around to see what's wrong with it and I'm at a complete loss. It keeps blowing the fuseable link 20a which I believe is for the ignition circuit. I replaced the coil, the distributer cap and button, and alternator because that's what I figured everything was pointing to and it fired right up like normal for a few minutes then blew the fuse again and I'm back to square one. Any ideas what it could be?

You have a direct short. You need to look around all the places wires run through the little metal loops that hold the wiring harness to the engine and fenders. If not there look for some place that has been rubbing. It's a direct short. It will burn the truck down if not found. You can use a test light or one of them 12 volt Pizarro buzzers from Radio Shack in place of the fuse. This way as you move wires around it will stop buzzing when the short is found. But it must blowing the fuse almost instantly when trying to use this method. Take your time, inspect every inch of the harness starting from the engine to the fuse panel, through the dash and out to the battery. It's just going to take time. There is no easy way to find them.

Best way is to get a wiring diagram of that fuse circuit and start unplugging things and narrowing it to a certain section of wire then go from there finding the short in that section. Also if it's effecting other circuits that helps too. The ESM section of the site should have wiring schematics and diagrams.

Ok thanks. I got a schematic and am going through it.

Fusible link blowing? So those things do work, hmmm. These are those lower rate amperage wire links from battery going to a larger sized wire if I'm correct. I would say this is a big issue for sure. Like camoit was saying, probably a good idea to find that short or you will burn that truck down. If it's one of the wires I mentioned above and depending on which one it was, the alternator positive to battery one would be my first choice of checking for shorting. It is a long wire going from alternator and depending on what truck you have, it follows the firewall from passenger side to drivers side then to battery.
If you have the stock amperage gauge that is installed in the lower console of some trucks, might be a good Idea to check that as well. Amperage gauges are just plain ole dangerous if not watched. I substituted mine for a voltage gauge which are much safer then a gauge having maximum amps traveling through it.
I hope you find the problem.

I had an older dodge kick my butt one day with the amp gauge. Nut backed out causing poor connection that would sometimes short and sometimes the car would do nothing since the fuse box's power went through that gauge.

It's the middle fuseable link the 20amp. I believe it runs into the harness into the engine control relay and from there to the ecu/ fuel pump/injectors/sensors. I believe I have a voltage gauge not an amp gauge.

You can start using jumper wires to bypass wire sections that you may think the problem is in. Pulling fuses also is a pretty good idea. Sounds like you are getting it cornered and will probably get it solved. I had a wiring problem for a long time and almost gave up until a member here mentioned something about the color codes on my issue. I'm no electrician and I would of never figured it out without help here.

I believe I found it. The fuel pump had a short in it. Halfway through dropping the tank now.

After a few days of head scratching after the new fuel pump I found the ground and power at the top of the tank had fused together. Just finished rewriting the fuel pump and it works. I should have it running tomorrow.