Disconnect the glow plug wire harness and connecting strap.
Use an ohmmeter to check the glow plugs [Figure 60-80-1].
Touch one probe to the end of the glow plug and the other probe to the body of the glow plug.
The reading should be approximately 0.9 ohm. If the resistance is infinite, the coil of the glow plug is broken. If the resistance is 0 the glow plug is short circuited.
Repeat the procedure for each glow plug.