1991 740 turbo. Raido suppression relay???
 

https://cimg6.ibsrv.net/gimg/volvofo...ecef4917a.jpeg
This 91 Volvo 740 Turbo has been sitting for about 5 months I went to start it and it would not start. A few cranks drove it for three blocks and it died would not not start up again I'm being told it's the radio suppression relay. Well I can't find any auto parts stores that have the part where do I get it and is it the issue? This was my dad's daily driver before he passed and it sat for 5 months before I took responsibly for her. She was his daily driver before she sat. Any advice helps. I had his 1994 940 and now his 1991 740. Trying to get them both up to running condition 940 blew oil out of the the turbo so I'm thinking the 740 would be a cheeper fix for the time being.

that relay number can be either the Radio Suppression Relay, or the AC Aux Cooling Fan relay. the RSR relay will have wire colors like this:
http://www.240turbo.com/relay1323592diagram.jpg


big chain auto supply stores have nothing for these cars other than zerex antifreeze, oil of choice, and wiper blades. you'll need to either find a local euro specialist store or get them from a volvo dealer, or online from the likes of fcpeuro.com or ipdusa.com or whatever.
https://www.fcpeuro.com/products/volvo-relay-1323592

Would this part be cause to the issue I mentioned?

the RSR supplies the power to the fuel injectors. no RSR == no run.

as the caption to that diagram says, you can unplug the relay, and temporarily jumper 30(4) to 87(3), and if the engine starts and runs with that jumper then your relay is likely bad. don't leave that jumper in place, as it leaves the fuel injection powered even when the ignition is off and would run down your battery.