[Martin Y]

The noise under the throttle is the idle speed control valve buzzing. Normal for it to make some sound while running though I'm not 100% sure when it should and shouldn't run.

 

[KRenshaw2000]

not sure about the noise

so we've established you're getting fuel to the fuel rail, 12v power is at the injectors

they either aren't firing because something isn't telling them to fire OR they aren't firing because they are blocked/stuck though that would be very weird if they were all like that.

if you end up accessing the injectors/fuel rail, do the bottle test and see if they are actually firing, but you did say the plugs were completely dry

I almost want to say you have no fuel but you've verified that already xD

I will check again tomorrow and do the bottle test and see if they are firing but yes the plugs are completely dry on the tips when I took them out. The noise is just a very strange noise that suddenly appeared. Its a constant quite whine when the ignition is on but stops when I remove the injector relay and its coming from underneath the throttle body, its a part which bolts to the bottom of the throttle body.

 

[Martin Y]

... its coming from underneath the throttle body, its a part which bolts to the bottom of the throttle body.

That's the ISC valve. It's driven by the ECU with a fairly low frequency PWM signal so it hums/buzzes. Can't remember quite what frequency. The 1.8 version (which they call an IAC rather than ISC but is the same type of valve) runs at 300-400 Hz but I believe the 1.6 version is slower.

 

[KRenshaw2000]

That's the ISC valve. It's driven by the ECU with a fairly low frequency PWM signal so it hums/buzzes. Can't remember quite what frequency. The 1.8 version (which they call an IAC rather than ISC but is the same type of valve) runs at 300-400 Hz but I believe the 1.6 version is slower.

Ah okay, I’ve only just heard it recently so I take it that it does it all the time.

 

[KRenshaw2000]

I now seem to have lost 12v power at the injectors any ideas

 

[Martin Y]

Well it looks* like the injectors get their 12V feed on the same white/red wire which also feeds power to the ISC valve. So if the ISC is humming at the same time as the injectors have no 12V, then that suggests a break in the wire. A connector is the obvious place to check. There seems to be a 6-pin connecter on the injector loom and the white/red wire goes through that.

*I downloaded a series photocopied Japanese wiring diagrams years ago; I'll try to find the link for you...

 

[KRenshaw2000]

Well it looks* like the injectors get their 12V feed on the same white/red wire which also feeds power to the ISC valve. So if the ISC is humming at the same time as the injectors have no 12V, then that suggests a break in the wire. A connector is the obvious place to check. There seems to be a 6-pin connecter on the injector loom and the white/red wire goes through that.

*I downloaded a series photocopied Japanese wiring diagrams years ago; I'll try to find the link for you...

I’ll check that out and have a look. If you could find the link that would be so much help thanks.

 

[Martin Y]

Here's that link I mentioned: EunosRoadster配線図 (do-da.co.jp)

Somewhat difficult having Japanese symbols for wire colours etc but a goldmine for Roadster-specific details when most diagrams out there are for Miatas.

 

[KRenshaw2000]

Here's that link I mentioned: EunosRoadster配線図 (do-da.co.jp)

Somewhat difficult having Japanese symbols for wire colours etc but a goldmine for Roadster-specific details when most diagrams out there are for Miatas.

Thank you

 

[KRenshaw2000]

Where exactly does the injectors get their 12v feed from. Is it directly from the ECU???

 

[guitaristanime]

1991_wiring.pdf (mellens.net)

EDIT ignore that its missing anything useful

 

[guitaristanime]

very much doubt its getting power from here, probably just signal

how about the INJ relay in the main box?

 

[KRenshaw2000]

View attachment 61168


very much doubt its getting power from here, probably just signal

how about the INJ relay in the main box?

Thank you. This will be so much help. Just got to get to the bottom of no 12v feed then hopefully it will run

 

[guitaristanime]

This is also interesting:

 

[KRenshaw2000]

This is also interesting:
View attachment 61169

That is very interesting, I’ll be sure to check all these. And let you guys know if I get it started

 

[Martin Y]

Looks like the "Inj" fuse feeds a white/green wire which goes to the main relay, then power leaves the relay on the white/red wire. That white/red feeds power to lots of items including the CAS and the ISC valve and the injectors. Now some of those items appear to be working okay so it's likely the white/red wire is getting power okay, but it may not be arriving at the injectors. The drawing shows a connector "X-03" on the injector loom. All the wires going to and from the injectors go though X-03, so that looks like a good place to check for volts.

 

[Martin Y]

Here's how they show the injector loom plug X-03, if it helps at all. I added colour spots for the ones I think I can read; all but the 3-coloured wire which is black/????/green.

 

[KRenshaw2000]

It’s just really frustrating me as I had 12v at the injectors before and I can’t see what I’ve done to lose the 12v feed

 

[KRenshaw2000]

But I do know that there is a wire and fuse that someone has added in which I don’t know what it’s for which connects to the red/white wire under the dashboard. I’ll take a picture when I get home and post it and see what you guys think.

 

[KRenshaw2000]

Another point is that it’s like got a relay for central locking and there’s wires added in so I’m a little confused.