2004 Mitsubishi Eclipse Keeps blowing Engine Fuse

I have a 2004 Eclipse RS that keeps blowing the #9 fuse in the engine compartment.This is causing a crank/no start condition. I found that by removing the #17 fuse from the passenger compartment that the #9 fuse doesn't blow. The fuse does not blow with the key inserted into the ignition, but it does blow when set to ACC/ON.

I've gotten the car to intermittently start but it shuts off at random. I don't suspect the ECU is bad due to the intermittent start. I do believe a wires insulation got damaged and is grounding somewhere.


I will begin diagnosing on saturday once my power probe comes in.

Here is my plan.
After looking at wiring diagrams, I’ve concluded it has to be the MFI circuit. But won’t be doing any work until Saturday.
1) Turn the key into a position that will trigger the fuse to blow to begin testing
2) use power probe to find which side of the fuse is shorted.
3) use the ECT3000 to help me find the short
4) if I can't find it using the ect3000 I plan to remove the computer from the equation and using the power probe to see if the fuse still blows

Questions that I have...
I have the wiring diagrams from AutoMate.

Should I have the key in the same position that is causing the condition? I think I should but I'm not 100% sure.

Should I focus on the power distribution part of the diagram or the ignition switch circuit or the MFI Circuit? I know the starter circuit is fine because it is cranking

Is there anything I’m missing?

Note: I’m not a technician. I just like working on cars.

you may be able to start troubleshooting now with a test light unplug circuit in question scanner danner uses power probe too but a lot can be found with test light just be careful not to apply power to driver a description of codes in question and thourough explanation of symptoms will help us help you also try to put diagram up too

I have a test light but I haven't really had the time to check the car since it happened. There aren't any codes, but when the short occurs it creates a no communication issue. When the car does decide to run it does get communication. I'm pretty sure it's a wire that's shorted, not a bad module. I just included the wiring diagram for the MFI circuit. Thanks for the tip.

I thnik you can verify power and ground to a module on gound I don't think you wanna see more than .01 volts

A good way to find a short that is blowing a fuse is to replace the fuse with a suitable wattage bulb say 5 watt. The short can only be on the output side of the fuse not the supply.
What is the factory specified amps rating of fuse 9 and fuse 17 ?
and what are they supplying particularly fuse 17 ?

Fuse 9 is a 20 amp fuse and fuse 17 is 7.5 amps. Fuse 17 lists it as ECM, Fuel pump relay, and PCM.
If I hooked up a 5 watt light into the circuit, I suppose I could do a wiggle test.
To me, it looks like a few other things splice into fuse 17. But I'm not super experienced reading wiring diagrams.

Quick glance it seems like Fuse 17 feeds the ECM. My hunch is when you pull out this fuse, the ECM won't (big guess) control the MFI relay which feeds power to lots of other things.

Without Fuse 17, does the White Violet wire connecting the MFI relay to ECM, get a ground when you do ACC/ON? Poke a hole in wire for speed, and no need to insert another fuse 9. Just wondering how many fuses have you gone through lol?

Which one's yours?

It might be worth pulling the fuel pump relay to see what happens.

It’s the 2.4 liter no sportstronic with automatic transmission.
I will test that wire for ground as soon as I get back under the hood and report back. I went through 3 fuses before just throwing in a circuit breaker.

I’ve also disconnected the fuel pump but did not do the relays yet because it’s hard to get my hands in the space to pull them out. I will try that and see if it gives me any direction.

Pretty sure I found it! I decided to start with a circuit breaker in the fuse and did the wiggle test. I seen that the diagram showed the fuel injectors which was interesting considering that it’s right by a heat source... after repeated wiggle tests I found one particular spot that would trigger my circuit breaker quickly. I cut open the harness and found a red wire with a small gash. Zoomed in on my phone to see it better. I’ve inclede pictures and will let you know once I repair the wire.