Finally got to the stage in my build where everything is together and it was time to get the car running. I connected the laptop to ms via usb-serial, and have been just setting up the base stuff ready for the first start.

I then pulled the fuel relay and was trying to check the timing (I have had the CAS off to install a coolant reroute so I'm pretty sure the timing is probably way out).

I connected the timing light to the intake manifold (ground) and the alternator (have also tried the 12v blue plug source) and had the induction loop around cylinder 1 ignition cable. Turned the car over a few times and no light. Checked the light on another car and it's working fine.

So, then I did probably a stupid thing and plugged the relay back in, in the hope that I could just get it running and perhaps check the timing that way, thinking maybe the battery didn't have enough juice?

It turned over, didn't fire, but there was a loud bang which scared the crap out of me, so I stopped.

I've taken the spark plug out of cylinder 1 and tried turning the car over a few times to check for spark (relay back out by the way!). And not only is there no spark, I can now no longer connect to the ECU, so I don't know if there was no spark before, or whether the ecu is simply not working and not telling the spark plug to ignite.

So, yeah a bad day in all, but I can't move forward with anything if I can't connect to the ecu. Looking at some other threads I did download the port checker software, and it came back with:


COM3 Opened
115200 baud
No connection made.
9600 baud
No connection made.


1 valid port found.


But tuner studio just simply cannot see the ecu at all to connect to. So, hoping someone here can help.

 

I'm just now starting my morning coffee. Let me get back to you when I can brain.

 

Thanks Sixshooter, that must have been a really large coffee.

So, I have managed to reconnect to it, it seems that it won't connect when the fuel inj relay is pulled, is that normal? My battery is rather flakey I think and I keep having to recharge it, not sure if a low voltage would cause issues like that, seems a bit of a stretch but...

 

Are you using the active high fuel pump circuit? If so, did you pull the appropriate fuse?

Good way to know is if you used trubokitty instructions it does not use that circuit. DIYAutotune instructions I believe set you up that way.

Low voltage could cause it not to see the ecu, the ecu wont power on. A strong battery is always recommended.

 

ECU is powered off the fuel injector relay, no power no connection. If you ever lose connection again, it's most commonly a bad cable, driver issues, or no power. Get out the multimeter and you would see that there's no power to the ECU when the injector relay is pulled.

 

Unrelated to the ECU, but generally if you get a big old boom when cranking before having set timing etc, it's just the fuel igniting on the intake stroke and blasting backwards through the intake manifold (ie: ignition timing is off enough that it sparks when the intake valves are open).
You can get some pretty cool fireballs out of the throttle doing that.

Usually it doesn't do any damage, but dont make a habit of it.
Worst that normally happens is a vac line or something blows off, but the force can sometimes take out a MAP sensor (especially if it's mounted right at the head)


But yeah, unrelated to the ECU not reading.

 

Yep, it was the fuel inj relay that I had unplugged.