I have been having the strangest issue with my '03 evo 8 recently. This has happened on three separate occasions. I would be rolling to a stop at slow, parking lot speeds. Throw the car into neutral and coast to a stop. As the car stops, the engine dies. When trying to start it again, the starter turns, but the engine does not ignite. Each time this was because the 20A fuse for the ecu popped and the circuit was no longer closed. Each time I replace the fuse and all is well as if nothing happened. Between the first time and second time, I drove less than 5 miles. However between the 2nd and 3rd (and last) time, I drove like 110 miles or so in various conditions.

I don't know a whole lot about electrical engineering, so I'm not quite sure how to diagnose this issue. Initially, I looked under the car and saw the rubber sheathing for the AEM wideband o2 sensor on the downpipe was coming apart. It didn't appear to have affected any of the wires inside the sheathing, but I wrapped it in heat resistant tape anyway. Otherwise I didn't anything that was obvious.

I found the link to the wiring diagram: http://www.lilevo.com/mirage/EVO%208...l%20Manual.pdf and from what I can tell, the fuel pump is on the same circuit. Is this correct? If so, I would be inclined to pull the pump out of the tank and take a look at the wiring. I remember a few years ago when I installed the walbro 255, one of the pins in the fuel pump holder (for lack of a better word) came loose and I pushed it back in. Perhaps it didn't seat well and is shorting out? Again I don't know much about all this so I'm looking for help on how to track down what's causing this issue.

 

Hmm, Interested in the outcome of this

 

Man, I got all excited to see a response, lol. I am stumped here.

 

I thought you might, as I typed it, but went with it anyway

 

looking at the schematic...

it looks like that 20amp fuse powers the MFI relay , the ecu and the ecu battery backup.

i would start by looking at the relay.
next would be the ecu.

 

Do you have gauges or other wired into the harness?

 

Found this thread. Sounds similar.

https://www.evolutionm.net/forums/ev...hen-blows.html

 

oh...yea...
MFI relay powers basically all your MFI sensors... so if any of them have a short.. that will do it.

 

Ok, so dumb question, how to I check the relay? Aside from looking for obvious visual issues.

The AEM wideband o2 sensor signal wire goes into the rear o2 sensor pin on the ecu.

 

wait what? Why is your gauge hooked into your ECU

 

The AEM wideband o2 sensor signal wire goes into the rear o2 sensor pin on the ecu.


that is where i would look first...
if its shorted, would blow that fuse.

 

Whats the signal wire for? Ive never hooked up my wideband to my ecu

 

It's the NB sensors you should be looking at.
The 4 wire ones have the heater powered by 12v from the ECU fuse.

 

I would have assumed this is just common knowledge, I apologize. But I wired the AEM wideband into the rear o2 sensor input on the ecu. This allows me to log accurate AFR. Here is the post I used to do it: https://www.evolutionm.net/forums/la...o-evoscan.html

NB wires? Sorry, not sure what that is referring to. Can you clarify?

I think at this point, I plan to just rip out the aftermarket gauges I have (boost and wideband), remove the radio and harness (radio decided to die recently anyway) and see if that resolves the issue. If not I can start looking into the MPI relay I guess?

 

Oh that makes sense.. I blanked, I just use a serial cable =O