I’m not 100% sure the factory style GPC in the Bullnose trucks does the afterglow. Remember, the 83-86 6.9 in the Bullnose uses a controller that threads into the back of the drivers side head. This style controller sends 12 volts to the second solenoid on the passenger side fender. I think it just comes on for a set time, and shuts off. There is no current sensing on this style controller. This is the style that, if/when it fails, it fails in the on position, burning out the glow plugs. I’ve read several times of people asking why my WTS light comes on driving down the road. There is no “intelligence” to this controller. This is why most upgrade to the solid state controller, or disable the factory controller, and run a manual push button.
The 87 up controller is the solid state controller that most of us are familiar with. It is the one that is all contained on the back of the intake, with the 2 yellow wires leading to it (or on the valve cover in the factory turbo, and with some of the aftermarket kits). This controller senses current draw, and cycles the plugs accordingly. It does the afterglow, and it normally fails safe, and won’t burn out the plugs. But this current sensing is also what causes the hard starting issues, because if a plug fails, or there’s a wiring issue, it will short cycle the plugs (the immediate click, click,click) and not heat the plugs. This is one why I normally install a manual override push button, that way if the controller doesn’t cycle at all, or short cycles, I can push a button and heat the plugs, even if some of the plugs have failed, I can heat the ones that are left and likely get it started. It might run rough for a bit, but running on 4 or 5 cylinders, roughly, is better than not running at all.
If all else fails, I normally carry a can of ether, and use it properly and get the truck started. Not ideal, but I can disable the glow plugs system fairly easily, quick shot on the air filter, and it will normally fire up. Also, don’t think that using ether properly will turn it into a “ether addict”. I’ve had times when the plugs weren’t working and used ether to get it started, sometimes for a week or three. After repairing the glow plugs, it would start just fine. The big thing is the proper use...... don’t hose it down, just a quick shot. If it gets to the point you have to use and entire can of ether to get it started, you have some other problem.
