ECU/Ground/ Wiring question- Im stumped

[xyoufailmex]

Hey guys. I currently have a S13 with a Blacktop S13 SR20 in it. My struggles first peeped their heads about 2 months ago. Randomly one day, the car wouldnt start. After 2 days of voltage testing, fuel pump and ignition testing, etc. the car finally started after removing the harness and putting it back in, and tightening it a little. Its ran fine ever since, until I recently brought my car down to install a FMIC and relocate the battery to the trunk. Never even touched the ECU or came close to it. Well, I get the FMIC isntall done and pressure tested, and I get the battery hooked up. Turn the key on, and everything lights up, power to everything. I go to crank, and it just spins over. Turn the key off, and back on, and it turns out my uber loud walbro isnt even priming. I mess with the ECU some more, remembering my past troubles, to no avail. So, I remove the cover on my ECU and dismount it. I take a test light to the inside of it, and start hitting the pins that connect to the circuit board. Well, I notice when I hit one of the pins, the pump primed and the ECU light came on. So I try to crank, nothing. I keep messing around with the test light, and cranking, and eventually it cranks. It runs GREAT after that. I drove it around town, boosting with the new FMIC, came back and parked it and tried to recrank. Nothing. I do the same thing to the same pin, and nothing. After 20 minutes of messing with the test light, it finally cranks. Ive also noticed my ECU under hood relay buzzing when I hit it right with the test light.

Ive tried checking every wire and connection I could find, but to no avail. Any ideas?

[xyoufailmex]

Cmon, any ideas? I know you guys are smarter than the Z ilvia guys...

[SpeedRacer1]

Some things just need to be diagnosed in person. Sounds like you have some issues with the connectors or wiring from the swap.

[xyoufailmex]

The thing I dont get is, it runs fine once it cranks. Thats the main sympton I was looking at that seems like it could help you guys point me towards something.

[karmakaze]

The thing I dont get is, it runs fine once it cranks. Thats the main sympton I was looking at that seems like it could help you guys point me towards something.

what type of cable did you use to relocate your battery?

[xyoufailmex]

I used a heavy duty 4ga battery cable for the hot and ground. The only questionable problem is that Im grounded to the strut tower. I tried running a jumper cable from the negative on the battery to the factory ground on the intake manifold, to no avail.

[draggin93]

Your battery should be grounded to the chassis as close as possible to where it is located. Any grounds that originally were connected to your battery should be connected to the chassis.

I wouldn't ground the battery to the strut tower. It may check out fine with a multimeter, but under load (starting) it may drop voltage and affect some of your electronic components.

[tonis56]

old thread yes.. but i seem to be having the same problems as you. Just wondering if you have made any progress??

tony-

[Kalypso]

very old... but im back again

whats a good place to ground the ecu
Modified by Kalypso123 at 5:09 AM 7/13/2008