Originally Posted by biopete

*Instead of pulling glow plugs and watching them get hot* , put a jumper wire from battery and touch it to each pin on plug. See if you get a good spark. If it does, its drawing current good and hard which means it should get hot. That's my friend's dead simple way to test glow plugs. He's an electrical engineer.

If you want to get fancy , buy a cheap ammeter that measures 25 amps at least. I got a meter that is for dash mounting at Harbor Freight for like $5.00 or something. I put a long wire with clip that goes to the battery on the B+ term and a wire on the other term. Strip the end of the other wire and stick it in a glow plug pin on the plug harness. A good glow plug draws 20 to 25 amps.

Thats it. No need to pull glow plugs. My understanding is it is physically impossible for plugs to not get hot if they are drawing the right amount of amps. I'm no electrical engineer though.