What a horrible past weekend I have had. Wrong parts were recieved, tranny took a shit on sunday but the car was still driveable just grinded 4th bad. Sunday night the car broke down and wouldnt start. I found the engine fuse under the hood was blown. Replaced it and it blew again immediately. It blew probably 3 or 4 before I towed it home.

Tuesday put a new fuse in it and it started right up and ran fine. Thursday again started right up, took it for a drive just around the block a few times to see if it was going to blow them again and sure enough after ab 20 minutes it blew the same fuse. 4 fuses later I towed it home again and thats where it sits.

I have looked over the wiring and nothing obvious is shorted out. It is deffinately heat related. My main question is what circuit does that fuse provide power to? Is it everything under the hood, from the ECU to the sensors? Where should I start looking

Sounds like either a bad ground causing high resistance increasing current and popping the fuse or a short in the wiring from moving around. Double and cripple check your wiring

Yea I plan on it, its going to be hard to check it with all of the wiring in loom, I was hoping to get some idea of what all goes through that fuse. I will be looking into it this weekend and maybe something will turn up.

So, I've been looking over the wiring diagram in my FSM tonight and I have some bad news for you. The "engine" fuse is what supplies power to..., cruise, charging system, ignition system, MFI system, starting system, and theft system. So its hard to really narrow that down unfortunately. One way to help is to see which side is grounded out, causing the popped fuse. So if its popping fuses as soon as you stick them in connect the positive side of your DVOM to the battery + and the negative where the fuse terminals would go. If you get a 12v on one side and not the other, then thats the side that your issue is in.

I'm willing to bet you have a short to ground somewhere in your MFI circuit. The spots that I'm looking at on my FSM are going to be from the fuse box to the junction block((A-83) which is wrapped in plastic underneath the fuse box), the transaxle range switch(if your auto), from the junction block to the ASD relays, from the ASD relays to the fuel pump, and another to another one of the ASD relays, to another junction block(A-82, under the fuse box) then to your ECU, your alternator, your ignition coil, your O2 sensor, and your injectors.

So if you have messed with any areas of the harness that is listed about that would be the first place to check your wiring. If you still haven't figured it out by Sunday/Monday let me know(I think your in Columbia) and I can ride down and help you figured it out(I may need some gas money :P ) If you need me to elaborate on anything that I've said above just let me know and I'll try to explain it in better detail! Good luck!

EDIT: My FSM is a 1998 Talon FSM, so while everything should be the same, just wanted to throw that disclaimer out there.

damn not really what i wanted to hear. I have done tons of rewiring with the car with MS and all so there is a lot of potential for shorted wiring I guess. Almost all of it is heat shrinked which is a good thing. Ill let you guys know if I find anything out.

In a nutshell how did you wire in the MS? Did you leave the stock ecu or did you "piggy back it" with the stock harness still in?

I would say ground. I forgot mine on the trans and went to start it and pop! So go around and look for any corrosion or loose grounds that's the easiest thing. Also Ive had one of those weeks! Your not alone haha.

Yes the stock ECU is still in the car. It has given me so many weird issues over the last couple years I am buying MS2 in a few weeks and going full stand alone. I will check all the grounds and test the continuity of the circuit to ground, may even try to get the car to shut off again and then start testing it.

If its not a bad ecu megasquirt probably won't fix it. I would diagnose then install MS

If his issue is in the harness or a ground, when he installs the MS2 as a stand alone it would fix the issues because he would be creating an entirely new harness and grounds.... Seems like a roundabout way of fixing it but it could fix it none the less. If its not broke don't fix it, and when it does break upgrade it :P

Originally posted by Slo2g
If its not broke don't fix it, and when it does break upgrade it :P

Well said

I was planning on fixing the issue before tearing into the wiring with MS2 install. However if I can not track the issue down then yes I will be putting MS2 in within a month or so and that will take care of the issue. Will keep you guys posted on what I find out. Ended up having to work tmrw so may not get much done till sunday

Did a little digging in the car today. Did some testing with in the fuse box and found that when the key is turned to the on position there is power on the 'out' let of the fuse. So with the fuse out there is 12v on the right leg. Which is the power in. But with the key on there is also 11-12v on the left terminal of the fuse. When I unplug the bottom plug on the stock ECU the power goes away. Can anyone verify if this is correct on a running car?

With the fuse unplugged you should only have power on one side.if you have power on both then the fuse is there for no reason. Sounds like you have a short to power somwhere on that circuit.

So did some more digging today. There are two wires coming off the fuse box, one runs to the ECU and one runs to the ASD relay. The wire coming from the ECU is providing power to the other side of the fuse.

So what does that mean? Current is backfeeding through the ECU? So either the stock ECU is shorted or another wiring is shorted and its passing through the ECU

More than likely the later if the two.

yea thats what i was thinking. Looks like more investigating next weekend. Making progress at least.

It's really common for the wiring running along the driver's side of the valve cover to melt to the EGR tube below the throttle body. You might not be able to see it without unbolting the harness. Just mentioning because you said it was heat related.