My 1980 300SD is having trouble with cold starts. I first noticed this at the end of last winter, but with warmer weather it disappeared. Was fine all summer. A couple weeks ago I adjusted the valves and after that it still started fine. Now the weather has gotten colder and as it got down to 45 deg it would start, but then run very rough. By applying some throttle and increasing the speed it would smooth out. Now that it's dropped into the 30s it's gotten worse and actually difficult to start, though it will fire up after more cranking. When it does start, sounds like it's not firing on all cylinders and shakes. The problem goes away after a few mins of running. Warm starting is smooth and OK.
So, my first thought was that there must be one or two glow plugs gone bad. I pulled the connector at the glow plug relay and all wires to the plugs indicate 1 ohm. I thought they were supposed to be more like .5 ohm, but I checked a brand new one with the same meter and it also indicates 1 ohm. I get 12V to light a test light at all the glow plug terminals as well. The only strange thing was at first it seemed I didn't have voltage at the last 2 plugs. I was pushing pretty hard with the test light pointed tip and also tried hooking a test lead jumper to the plug and connected it to the test light For some reason, those 2 wouldn't light the test light at first, but now it's definitely there. It probably was just that I wasn't getting a good contact.
When activated, the glow plugs have voltage for I'd say about a minute or so. The glow plug light on the dash goes out after maybe 10 secs, like normal and 12V remains on the plugs for I'd say a min after the dash light indicator goes out. Then there is a click from the relay and they go out. So, all this seems perfectly normal,
So, I'm thinking I'm on the wrong track here. What should I check next? Could it be an injector problem? Is there any easy way to test them? I see in the shop manual they talk about how to test them in a test jig which sprays oil out of them, but lacking that what do I do? Also car has 125K miles and is in otherwise great shape. I did the timing chain test when I did the valves and there was no stretch, the timing marks line up at exactly zero deg.
Any suggestions would be appreciated.
Chet