Yet Another Spi Not Starting

Sidewalk ran like a dream yesterday but will not start this morning. I'm an emotional wreck. How I long for an old fashioned distributor with a mechanical /vacuum advance and an SU HS4.

Mine did the exact same thing.

I was reading Coolant Temp, Air Temp and Throttle position faults on my ACR4.

Had a fuel system code as well.

Cleared them all.

I had spark.

Disconnected all sensors to encourage default settings in MEMS but still wouldn't start.

Checked fuses A4 and C7 as these both have a role in fuel pump operation.

Checked volts on the black/ purple wire out of the fuel pump relay and they were very low.

Not enough to pull the relay in.

Tipped some fuel down its neck with all sensors disconnected and it started and kept running.

Plugged the sensors back in one by one and it immediately ran crap when the Coolant temp was plugged back in.

And it wouldn't start again.

ACR4 picked up a CTS code only this time.

Had a spare CTS replaced it and now it all works perfectly again.

I suspect some sort of back voltage through the common ECU sensor ground threw everything into confusion.

Thanks for that Wazzah. I'll order a new CTS and report back.

Last monday I optomistically booked an MOT test for next Monday and immediately the flexible joint in the exhaust downpipe broke so ordered a new one. After pulling off the old down pipe, I found that the access to the Temperature sensor made changeing it fairly easy so a new one is now in place and when the new downpipe was installed she started and has run fine since. Thank you all and I will report after the MOT.