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Fixing Main Relay on CRX Si 1990.

This problem have been hunting me for a number of years and finally I got it fixed.
    Symptoms: Car sometimes would start and die almost immediately especially if the weather is hot.
    Reason why car won't start: main relay wouldn't fire up the fuel pump due to the soldering cracks on Mian Relay PCB. Cracks would appear over time and can be re-soldered.

Main Relay Diagram

Testing the Main Relay


  1. Remove the main relay.
  2. Attach the battery positive terminal to the No. 4 terminal and the battery negative terminal to the No. 8 terminal of the main relay. Then check for continuity between the No. 5 terminal and No. 7 terminal of the main relay.
    • If there is continuity, go on to step 3.
    • If there is no continuity, replace the relay and retest.
  3. Attach the battery positive terminal to the No. 5 terminal and the battery negative terminal to the No. 2 terminal of the main relay. Then check that there is continuity between the No. 1 terminal and No. 3 terminal of the main relay.
    • If there is continuity, go on to step 4.
    • If there is no continuity, replace the relay and retest.
  4. Attach the battery positive terminal to the No. 3 terminal and battery negative terminal to the No. 8 terminal of the main relay. Then check that there is continuity between the No. 5 terminal and No. 7 terminal of the main relay.
    • If there is continuity, the relay is OK; If the fuel pump still does not work, go to Harness Test.
    • If there is no continuity, replace the relay and retest.



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Total messages: 3

main relay
posted by: Levi on Sunday, August 18, 2013 at 1:42 PM
Nice schematic. Love the test as well. Some people might not know how t do the actual test if they are not technicians.
Main Relay Repair
posted by: George on Tuesday, February 17, 2009 at 6:23 PM
The vibration cracks the joints on the relay tabs. The repair is easy if you can solder well. Open the case and you'll see the places needing resoldering.
Stupid thing goes bad
posted by: 91crx.si on Wednesday, October 22, 2008 at 9:23 PM
This relay went bad more often than not in my case. Changed 3 of them. Even on stock CRX with no aftermarket anything 8 years old at the time.
And I did not know how to fix it back then... too bad