Testing glow plugs

[1986Blazerk5]

My m1009 is hard to start think the glow plugs are bad how do you test to see if they are bad, i know the glow plug relay is good it is brand new, i heard of a way to check them with a multi meter or a test light but still confused how to do this right.

 

[doghead]

Your best bet is to learn to use the Tech Manuals and search function. Very easy to diagnose the Glow Plug sytem. Step by step instructions are in the TM. Many posts here also, with dozens of ways to test it.

 

[EO2NMCB]

"No light indicates a bad glow plug" That would only tell you that you have no voltage to the plug. Use a DMM ohm out the plug, a good GP will ohm out between 1-3. Above or below that and the plug is bad. If you should find a bad GP, you are most times better off replacing the set, since you then had higher voltage going to the other working plugs.

 

[K9Vic]

"No light indicates a bad glow plug" That would only tell you that you have no voltage to the plug. Use a DMM ohm out the plug, a good GP will ohm out between 1-3. Above or below that and the plug is bad. If you should find a bad GP, you are most times better off replacing the set, since you then had higher voltage going to the other working plugs.

I think he means you have the system off and put a test light on each glow plug with the green wire disconnected. You do not do anything with turning on the ignition, all you are doing is testing that the glow plug has a good ground internally from the positive terminal. If the test light does not light, then you have a bad glow plug as it can not make ground to power it. The test light connects to the 12volt side of the battery, you are just simply testing connectivity on each glow plug. This is how I tested mine and found I had two that were bad.