Fresh battery in meter. Meter set at 200 reads .5 with leads touching each other.
Meter set on 200, relay unplugged, touching one lead to tip of GP threads and other lead to top of valve cover I get consistant readings across all plugs of about 97.5. Checking against other potential good ground points in engine bay gets same readings.
Could they all go bad at once? Last replaced at 221K in Jan/05. Car at 336k now. This thing started like a trooper all winter without a block heater. Only started giving trouble a couple days after I installed a heat exchanger and went to a high ratio veggie oil blend right before a cold snap. Now with 3 hours on block heater its still a no go.
Not to get too off topic but IF I am reading the plugs correctly it would suggest that the veggie may have built up a bunch of carbon on my plugs to crash em. Viable theory?

__________________
84 300SD 274K
38K miles on flatplate heat exchanger and various diesel/veg blends. prior to that 4K miles on unheated veggie blends with kero and DinoD.