Testing glow plugs

[Hasdrubal]

Recently my M1009 motor has run a little rough for a 5-10 seconds on a cold morning start, made me wonder if one or two plugs have failed. Had the AC60's in for a few years, no problems. Seemed to remember a testing method was to use a test light connected to battery positive and place tip on glow plug spade, if it didn't light it had failed. Is this a sound method? Reason I ask is after performing said test all mine light up, so I was wondering if i could count on this method.Still unsure..

 

[CCATLETT1984]

unless you have changed the stock wiring for the glow plug power source from the resistor to the front battery, the 60g's are not the correct plug. Over time they will all burn out, since they are getting more voltage then designed to handle. The correct plugs are Wellman 070's. As you notice from the other poster, once a single plugs fails the voltage goes up, likewise for every failed plug after that. So once a failure occurs its a snowball effect.

 

[acetomatoco]

From the -20: Disconnect each glow plug lead and check for resistance between glow plug terminal and ground. Resistance should be 0.45-3 ohms (Wellman) or 1-3 ohms (GM). If any glow plug does not have the correct resistance, replace.