Just bought non-running 1990 780 4-cly Turbo and will not start. Have good 740 turbo to troubleshoot with. 780 turns over and has spark, but fuel pump relay does not click in start position (same relay clicks in my other car). I can hold pump relay (the one closest to me) closed and pump will run and car will start, but quits when release relay. I put test light across negative side of coil to ground and no light flashes (flashes on my good car). Replaced power stage and radio suppression relay, but nothing. One of the computers gone bad? Any other ideas? Thanks very much.