ECU dropping out.

[Knoxy]

I've bought the gbs chassis loom engine loom and emerald ECU. Everything plugs together as it should only thing I've had to do is connect the Mazda column switches to the loom. 

My problem is when the key is turned to position 3(start) the power to the ECU drops out but the car is still cranking over.

I've checked the battery voltage when cranking. 

My thinking is that there might be a relay for the ECU that's losing power when I turn the key. I dobt have a fuse or relay diagram from gbs so I'm not sure what is what.

The ECU powers up fine an does everything it should until start up.

 

Any suggestions?

 

Thanks.

[IanS]

You might have connected the ECU power to position 1 which is audio feed and is dropped whilst cranking (prevents tapes tangling)

ECU ignition live would be position 2

[blue]

Agree you have the ecu connected to the wrong wire on ingition switch - at least it's a simple fix 

 

[Knoxy]

ECU is on position 2. It only powers up when on second click. That's what I thought I had done initially so pulled the column connections apart just to check.

[Knoxy]

Could it be due to not having the alternator connected as the Mazda alternator requires the Mazda ECU for regulating voltage or something like that. So looking at alternatives together round this. 

According to the little wiring information I have for the loom. I have an ECU ignition relay no idea which one it is but if this hasn't got power might be my issue.

[Knoxy]

Ignore alternator stuff it still wants changing but nothing to do with my start issues.

I've worked out what all my relays are an there is an ECU one. On cranking its losing all voltage on both sides. Almost as if the starter Is drawing all the power. I'm confused might be a call to gbs on Tuesday.

[blue]

Hi can I ask what ign switch your using  does it only have 3 positions ? 

Position 1 is aux like radio etc 

Position 2 should be ign live 

And position 3 should be ign live AND cranking together 

Can you confirm this is happening as it might be you have the ign wires the wrong way wired 

[Knoxy]

I'm using Mazda mx5 column with 3 positions. Although I must admit that I haven't checked that position 3 is staying both live and cranking. What your saying blue makes sense. 

The loom has a optional wire for starter button. Might temporarily wire in a button on that see if it works.

[Knoxy]

Problem solved. I used the wrong second position  wire. The black/ white wire I used goes dead on cranking the blue wire that for some reason I'd taped up a few months back was wire I actually needed. Obvious when you have a wiring diagram that's correct an not relying on multimeter.

Now to get it firing out the exhaust not the inlet.

[blue]

Glad you found the problem