Needed to check for spark on my '93 Del Sol Model S.

Disconnected fuel pump relay under dash. Inserted my "in line" spark testing tool. Turned key. No sound from fuel pump. No spark on any plug.

Then, re-connected fuel pump relay, inserted in-line spark testing tool, turned key, car started and I saw spark on all.

Why wouldn't I see spark when the car cranks and with the fuel pump relay disconnected?

Thanks.

 

The main relay supplies voltage and ground to the ECU. If you disable the ECU, there will be no spark or fuel.

 

Ah! Thank you.