I hate winter! My truck has been not starting well for about 2 weeks now. Checked across the relay with my meter, it appears to working correctly. Turn on the key and I get voltage across it for about 10 sec. Checked the glow plugs, had 6 of them test open. Replaced all 8 last weekend. Started fine on Sunday and Monday, thought I had cured it. Now, starting this morning, it is back to its old tricks. I cycle the plugs, crank for 10 or so seconds, turn off the ignition, and repeat 1 or 2 more times and it starts, blowing white smoke for the first bit. If I plug it in, it will start fine. Only acts like this when it has sat for at least a few hours and got cold again. Any ideas what to check next??