Starting a little harder.

[psaboic]

1983 300D began starting a little harder recently. Only happens if the engine is stone cold or has sat for about 2 hours. Warm starts are fine. Sounds like classic glow plugs right? I thought so too. All the glow plugs read .4 ohms, the glow plug wires read .01 ohms. I have battery voltage at the glow plug relay and on both sides of the strip fuse. Turn the car to glow and all 5 plugs have battery voltage to them until the relay times out, so it seems the glow plug system is fine. No air in the fuel lines either. The only thing I think it could be is the battery. Battery still holds a charge of about 12.3 volts, and a little over 13.5 or so with the alternator running. However the battery is a 75 Month NAPA battery that according to the sticker has been in the car for roughly 100 months (Jan 2011). Suggestions?