Hey guys. I could really use some help, as electrical is not my forte, and I am super stumped. So, I've been rebuilding my Evo 8 the last 6 months after timing let go. I've gotten all the mechanical stuff done now, and am basically ready to start the car. However.. I started experiencing some weird issues.

Some background:
While the car was down having the motor rebuilt, I decided that it was a great time to do the JDM hvac swap. I had collected all the parts, and did my due diligence with the wiring following a known-good write-up. Once the engine was back in the bay and I had the engine bay harness fully connected, I added my battery to the mix so I could turn the key to ACC and test the hvac wiring to make sure I did it correctly. When I connected the battery terminals, nothing out of the ordinary happened, and I was able to successfully test the new hvac system; blower speeds worked and the servo/direction motors worked, all as they should. Yay me! At this point, I did some wire management before putting the dashboard back in the car and continuing on with some mechanical stuff I needed to do (brakes, exhaust, etc). Two weeks after I initially tested the hvac system, I was at the point where I was ready to tackle wiring in the new gauges I got for the car (boost, oil temp, oil pressure, and afr). During those two weeks of in between time, I did not have the battery connected at all. When I went to put the battery back in so I could test for a good ignition wire power source, issues started happening. Note: new gauges have not yet been wired in yet because of said issues.

The problem:
Keep in mind, throughout all of this, the key is not in the car at all. The engine bay harness is fully connected, and the interior ground tails that come off the dash harness are all connected.
When I connect the battery terminals, all my lights come on. And by all, I mean high beams, low beams, blinkers front and rear, running lights front/rear/fenders, and brake lights. If the gauge cluster is connected, the fuel pump comes on. All these things happen even with light plugs (headlight/blinker stalk, and fog light switch) unplugged.

Troubleshooting:
I'll lead by saying I am absolutely clueless about electrical, so I'm sure I'm missing something somewhere with reading the wiring diagrams, but I've had a couple people try to teach/show me some things with that.
I followed the wiring diagrams to try to find things the lights all had in common. What I found was that things ran through a "front ecu" in the engine bay fuse box, and ran through the ETACS box that's connected to the interior junction/fuse box. If I remove the front ecu and separate the ETACS box from the junction box, then my symptoms go away. If I leave the front ecu in place and just separate the ETACS box, then my side markers and DRL's turn off but my highs/lows and tails are still on. Removing various combinations of relays from the junction box had no effect. If I leave the front ecu connected, and remove the junction box completely from the car, then my side markers, DRL's, and driver side taillights turn off but the rest still come on.

Does anybody understand how the junction box/interior fuse box, the ETACS, and front ecu get their power? What else can I check?

 

Half way through reading this I thought it could have been water getting into the use box under the hood, but now i'm thinking that you might have to bust out the DMM and figure out what is triggering all those relays at once. It might also be worth switching out those ECU/modules out with a known working one from a friend to see if it makes a difference.

IIRC the fuse box under the hood on the driver side gets it's power straight from the battery through one of the two fuse links. The starter signal lives there too.

 

What about the relays that live in a separate panel on the side of the main box, where do they get their power from?

 

SOLVED. Long story short, I did a dumb.

When I had taken everything out of the car, I didn't pay enough attention to how the battery terminals and cables were set up. I had attached the chassis/transmission ground cable to the positive junction block at the terminal. *HEAD DESK* Anywho, it's fixed and now I'm troubleshooting a no-start issue.

 

I have had a no start issue before. The popular cause nowadays is the OMNI 4 bar map sensor failing prematurely.

Batteries can die and not have the ability to deliver enough cranking amps. Make sure the battery is charged and at full cranking amperage.

Otherwise check to make sure the starter is being engaged, spark is being delivered and the fuel pump is running.

 

I've confirmed fuel (pulled the feed line from the rail, watched fuel spit out), confirmed spark (pulled each spark plug and watched them spark as I cranked the car over). I've confirmed the crank position sensor trigger wheel is installed the correct direction, the crank position sensor is brand new. I've confirmed the camshaft position sensor trigger wheel is installed in the correct direction, and I'm looking through my receipts to see if I replaced the camshaft position sensor (cuz I honestly can't remember off the top of my head). I've triple and quadruple checked timing multiple times throughout the course of this whole rebuild by hand cranking it over and over and over again, and everything lines back up.

Without buying a new MAP sensor, is there a way to see if my current one is bad?

 

I'm pretty sure the ECU does not look at the MAF (or MAP in this case) during cranking. Its values are set mostly based on the coolant temp. So it should fire without this, and at worst just sputter and die after firing. If I'm wrong about this though someone please chime in.

 

Are the plugs wet or dry after cranking?

You can quickly check your Omni 4 bar output voltage at atmospheric pressure with your digital multimeter:
Pin 1 = Sensor ground
Pin 2 = MAP Signal
Pin 3 = +5V supply to sensor
Pin 2 Voltage out/signal = 5 X (.002421 X Pressure in KPA - .00842)
Atmospheric pressure is approx. 100 KPA = 5 X (.002421 X 100 - .00842) = 1.168 volts

 

Plugs are definitely wet; they're getting fuel. They're even trying to fire, as I can see carbon on the plug tips when I pull them.

I had someone much smarter than me come out and help me this weekend and check over some things. We think we found the culprit (timing is a full tooth off. How exactly that happened, not sure; I could have sworn I had double/triple/quadruple checked things before putting the ATI balancer on, but... Alas, here I sit). I'm getting that fixed this week (hopefully), so I'll see how things go.

 

Glad you got it sorted.