My 3B project (ongoing)

[Dobby84]

Okay I'll try spend some time on it tomorrow and try find the issue. Cap and arm are pretty much brand new. Gonna check the ecu power too

[Dobby84]

Does anyone know what the impedance should be on The cranc sensors? And where are they? Are they both below under the cam wheel or is it just one there?

[Bowie69]

They're on the bellhousing, the connector for them is above the fuel pressure regulator.

If they are the same, likely they are OK - I don't have an impedance figure.

[Dobby84]

Ah okay those ones.
cheers

[newsh]

Check the dizzy timing is spot on too.

[Dobby84]

Just checked the power to the ecu. I have 12v at pin 3 fuel pump relay control and pin 27.

[Dobby84]

Also have 0v at the injectors

[Joss]

To add to Dobby’s info. I found a burnt wire that over heated right way through the loom back to the fuse box. Had to cut it out and solder in a replacement. You can see it in the pics from the back of the read plug. Lucky the car hadn’t caught fire tbh but can’t tell how long this has been like it. Could have been years. I’ll check with dobby but can someone link me to a fuse box diagram so I can check what it was supposed to be powering as we suspect the old fan which would explain why it was having issues.

[newsh]

To add to Dobby’s info. I found a burnt wire that over heated right way through the loom back to the fuse box. Had to cut it out and solder in a replacement. You can see it in the pics from the back of the read plug. Lucky the car hadn’t caught fire tbh but can’t tell how long this has been like it. Could have been years. I’ll check with dobby but can someone link me to a fuse box diagram so I can check what it was supposed to be powering as we suspect the old fan which would explain why it was having issues.

The fuel pump fuse melted on mine, I cleaned it up, fitted a new fuse and relayed the pump from the battery.

[Dobby84]

Checked all fuses with a multimeter and all seemed okay

[twoqu]

Have you been jump starting this? They don't seem to like that much!
Think you should have 12V on the injectors with ign on as thats from the holding relay in the ecu. Not sure this expanation makes it any clearer:

https://www.s2forum.com/forum/technical/engine-and-turbo/86186-audi-s2-3b-won-t-start-please-help?p=1337220#post1337220

Sounds like its connected to the fuel pump relay somehow as it powers the fuel pump and injectors.

[twoqu]

I thought pin 3 was the earth from the ecu to close the contacts in the fuel pump relay. If the wire replaced is a brown one with a coloured tracer its usually earth related.
So when the ecu sees the car cranking from the rpm sensor it activates the relay, clossing the contacts to the injectors and the fuel pump.

[Joss]

Have you been jump starting this? They don't seem to like that much!
Think you should have 12V on the injectors with ign on as thats from the holding relay in the ecu. Not sure this expanation makes it any clearer:

https://www.s2forum.com/forum/technical/engine-and-turbo/86186-audi-s2-3b-won-t-start-please-help?p=1337220#post1337220

Sounds like its connected to the fuel pump relay somehow as it powers the fuel pump and injectors.

No, not bee jump starting it. So many things seem to hate this. I’ve charged the battery so all from it’s own supply. Yes reading your other post that seems to make sense to me so should sit at 12v when ready to fire injectors.

[Joss]

I thought pin 3 was the earth from the ecu to close the contacts in the fuel pump relay. If the wire replaced is a brown one with a coloured tracer its usually earth related.
So when the ecu sees the car cranking from the rpm sensor it activates the relay, clossing the contacts to the injectors and the fuel pump.

Wire replaced was brown only and traced back to many wires. For some reason I didn’t actually check what it was as I just wanted to swap it out ,but I assume either 12v or earth. I’ll check it tomorrow and confirm. I think you may be right. It’s not seeing the car crank and so isn’t signalling to fire.

[Dobby84]

By the way, just a bit of recent history in regards to the car running..... For the last year it has been sat not doing much but once a week I'd start it and it would start straight away. No jump start just on the battery (disconnected when not used) a few months ago I moved it to Bournemouth, drove it onto the trailer to get it there, drove it off the trailer with no issues, a few weeks later nothing........ It turns over but doesn't run. Very odd in my opinion......