83 300sd starting problem. Glow plug relay?
 

Hello, Can anyone help me with my starting issue. I have purchased my second (used) glow plug relay for the 3oo sd I own. The glow plug light comes on intermittently and then goes out. Does not stay on for even 1 second. And it does not initially light up for at least a full second after the key is turned on. I struggle to get the car started and once it is running I can shut it off and start it with no problems. The glow plug light even lights up correctly when the car is warmed up. Does anyone have any insight into this? I put in new glow plugs last fall and replaced the relay earlier in late summer last year when the first one failed. As soon as I put in the newer relay the car started normal. Over a month ago I started having the same problems with starting. Please help! thanks.

New relay, clean all associated contacts for ignition, relay, glow plugs, glow plug indicator light, chassis grounds and battery terminals, and make sure they make positive contact with each other when fastened.