This is my second or third attempt at seeking help here. I have a 1984 Mercedes benz 300 sd turbo diesel. Lately, it has failed to start. I replaced the glow plugs approximately 7 seven months ago. I have checked several things (relay,etc.). It turns over fine but will start. I have also tried engine starter fluid and it still will not start. I don't believe it is anything major, but, rather minor and needs someone with a more mechanical know how. Can anyone offer further suggestions?

 

The battery is fine.