starting problems
 

I have an 83 3oosd.
Never had hard starting, now the glow light does not come on and it takes two time to start cold with a lot of smoke.
I changed out the glow plugs approx 2 years ago.
The relay shuts off after approx 30 seconds with no starting and the fuse is good.

Any thoughts??/

How is the GP wiring?
 

Unplug the 5-wire plug from the top of the relay. Check resistance between the contacts on the plug to ground. You should measure about 1-2 ohm.

You did not indicate how you know the relay is working, (audibly or with a voltmeter?). I you have not done so yet, check that you have 12V output at the relay when it is on.