I have a 1981 300SD with a glow plug relay problem.
When the key is turned on the relay clicks twice, on then right off. The relay sends power to the glow plugs for just a second or two. I took the relay apart and cleaned the contact points and every thing looked ok. Is there anything else that could cause the relay to cycle so fast, the glow plugs don't get any power so it is very hard to start these days. The glow plugs have been replaced in the last 3-4 years, so I would hope they haven't gone bad yet. The relay seems to be my problem. Just want to make sure I not missing some other test before I purchase a new relay. I looked on FastLane and they have a relay with 4 glow plugs for $87 and just a relay for $120. Anyone know why the one with 4 plugs is so much cheaper.
Thanks for any advice you can give.

Martin
Edmonds, WA
1981 300SD 197,000 miles