Larry,
I do a real low tech check on glow plugs. I use a pair of jumper cables on a 12v tractor battery. I grab the stud bolt with the positive and hold the hex head or threads in the neg. If it doesn't heat up in 5-8 seconds, start smoking a little and turning red, chances are good that they are no good. I order my Iseki glow plugs right from Derrick at Rainbow dist. in Hawaii. He's great to work with and service is awesome. Shipping in a couple days.
Nick