I was reading some of the posts about testing the glow plug relay for 12 volts on both lugs. I turned the key on first to energize the glow plugs with a multimeter across the passenger side battery. It dropped the voltage in the whole system from 12.76 to about 11.76 volts. So I knew the glow plugs were drawing something. I then repeated this procedure and tried to get a reading off what I believe is the glow plug relay. It even looks exactly the same as the picture on the parts website. Thing is I couldn't get a voltage reading anywhere off of that relay! It was located almost in the center of the engine compartment directly above the passenger side valve cover, mounted perfectly horizontal. What's the deal? I tried it a couple of times because I thought I might not have a good ground. From what I saw the relay has two big lugs and two little ones. I swear I couldn't get a reading! Am I stupid or just acting that way? I ask because I want to make sure before I go out and buy those two new batteries tomorrow that they are really the problem with the engine not wanting to start. PS- I couldn't get an amp reading on the battery with the glow plugs energized because my multimeter said it would blow up at 10 amps. Thanks for any feedback.

 

Ground the negative probe of your multi meter to the engine block. With the glow plugs energized you should have somewhere around 12V on both of the big lugs of the solenoid using the positive probe of your multi meter.
The other test requires a inductive pick up type meter which clamps around the wire being tested.

 

Thanks for the feedback Sam. I did go ahead and buy those brandy new 875 cold cranking amp batteries from advance auto parts. I rechecked the voltage drop across the system when energizing the glow plugs. With the new batteries the voltage went from 12.54 volt to 12.40 volts. Quite a difference from the old batteries! If my memory serves me I think the formula for current is current=voltage/resistance. I think in old batteries when they get old their resistance goes up which reduces the available current for glow plugs/starter. About the current test, I figured it needed one of those clamp on meters. I used to have one till someone stole my tools last year. Funny thing is when I had it I couldn't figure out what I'd ever use it for. You know how that goes. Thanks for all the great feedback!