volvo 740 NOT START, unknow relay susspected

After i wash the engine , i drove little , and when i came back to my caraftera while the starter was not respond , after little reserch on the web how to inspect the problem i found a relay which sitting above the starter that do not transmit 12 v to the starter solonoid . i finaly i managed to start the car by bypassing the starter direct to th battery
my question is:
1.how do i check if this relay not working , i notice that 1 pin get 12 v constant and ather ground i belive , the 3 got the starter , but where the 4 come from?
2.could it be cancel ? i thing it might be not originaly sitting there since i did not find it in electricity diagram? what is function name ?
3
the Relays is : 4 Pin 12v 30A 4RA 003 510-08.
 
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