Ref Sensor low voltage
 

After getting the 87 924S started a few times with all the new parts, (sensors, coil, fuel pump, dme relay, injectors, dizzy, button,... back to no start...

Broke down and bought an oscope and am getting a signal on both sensors to the DME plug 8-27, 25-26 but the voltage is only 1 v not over 2 as is expected. I regapped closer to the flywheel, further from the flywheel, at the right spot.. still around 1v signal

What would cause this??

Thanks

Could be a corroded connector? Check at the connector at the intake manifold, then compare that to the signal at the ECU. If the connectors are original, they may be disintegrating, leading to questionable connections.

Of course, it could be the sensors.

Also, make sure that the pin on the flywheel protrudes by 0.5 mm from the edge of the flywheel, and that it is not magnetized.

I tracked a random no start on my 924S to the wiring harness. New sensors (for the wires) and a new harness for them back to the computer and haven't had any problems since. YMMV
Wires weren't so much corroded as fraying where they bent. Check the wires closely.

See my video below on the sensor voltages and how much impact the gap makes. If you are not seeing the pulse get bigger and smaller as you adjust the gap -- like in the video -- then either the signal isn't cleanly getting to the DME connector, or there is something wrong with the sensor, or the pin in the flywheel is missing/damaged/too short. You might try probing it on the sensor's connector, just to eliminate issues on the engine harness side. If it's fine at the connector under the hood, then you know it's the engine harness (probably frayed wires in the 3-Pin JPT connector). If you are still seeing 1 volt under the hood, regardless of gap, then swap the sensors and see if the issue stays with the sensor (in which case replace it) or stays with the ref sensor position (in which case, inspect the flywheel pin).



https://www.youtube.com/watch?v=m-gz13Nrih8&t=37s