The .049 glow plug ?

The failure modes I have noted in the decades of running glow motors:

Over Compressed engine
Fuel contamination
Over Voltage
Excessive Vibration
Poor quality filament
Poor quality plug/head construction (weld fails, or compression leak past electrode seal)
Engine wear particles contaminating the filament
Wrong heat range plug for the % of Nitro
Way too much Nitro


Of all these the most plugs I killed were from too much compression or over voltage

I think a couple of failed plugs were from old questionable fuel that left a fuzzy white contamination on them.... They would glow by battery but not run reliably off the juice

I also had a rash of plugs that the filament was off set to the side and intermittent shorts

On my larger engines I try hard to find the 2VDC plugs so I can use the Cyclon Lead acid 2VDC primary cells without a dropping resister

I found the Hobbico Deluxe Power Panel II that only outputs 1.2VDC but has Amps (current) control from 0 to 5 Amp. Highly recommended

Of course a bunch of Parallel attached 1.5VDC D cells works just fine