IDI BRONCO : I have noticed the same thing regarding manually goosing the GP after start, even though it doesn't get very cold here. I can *hear* the engine change tone as the engine warms up
I will point out I lost an alternator on my previous foray into glow plug relay that malfunctioned stuck ON. I suspect that once the engine caught, the voltage regulator pegged the alternator rotor full bore on in its attempt to hold the battery rail at 13.8 volts or so, but the alternator is rated 130 amps or so...and my glow plugs are drawing 25 amps each with the battery rail at 10 volts ( loaded with 200 amps - eight plugs ). So something had to give. No sooner than I replaced the alternator, the new one quickly finished every one of the glow plugs. I don't know if the old alternator had burned out any. At that time, I wasn't aware I had this much woe heading my way.
Anyway, once discovering my GP relay had welded-shut contacts, I replaced the relay. A week passed and it failed the same way, and took out the glow plugs again. Thoroughly disgusted and fearful of some hidden fault to ground in the glow plug circuit, I thoroughly inspected the wiring and found nothing wrong. I assumed it a strong possibility the controller itself was causing the relays to fail. I had seen a similar relay driver fail when a power supply capacitor became old and it's internal resistance went up, causing the coil drive to oscillate, causing the contact to make erratic contact which caused the contacts to weld. So, I bought a brand new Motorcraft name-brand controller. A few days later, it did the exact same thing! Thank goodness I still had the wrench handy to disconnect the battery when I noted the voltmeter failing to show the voltage increase when the relay was supposed to.
disconnect the plugs. Yup, the contacts were welded shut, again.
At this point, I went all manual with the same industrial contactor relay Wes Texas puts in his kits.
That was about three years ago.
No issues since.
During the summer in Southern California, i don't use my glow plugs, however, in the Winter, a few seconds pre-start glow saves a lot of work for the starter motor. I only need to use the plugs when the engine is cold. If the engine is still warm to the touch ( like it hasn't been down for over two to three hours ) , it will start right back up whether I glow or not.
I recently experienced a starter motor fail in such a manner where it gave a weak start and drew a *lot* of current.
It mimicked a bad battery or ground connection, as the voltage on the battery rail did not drop as much as expected. Turns out I had to run glow and starter simultaneously to get it started...really sluggish. The connections to it, and grounds, were sound. Electrical energy was going in, but not all that much mechanical energy coming out. My guess was maybe a shorted turn?
Oh, incidentally, I did remove the serpentine belt for the test start as I wanted to eliminate mechanical drag problems such as A/C compressor clutch malfunction, binding alternator bearings, binding tensioner bearings, etc. from consideration.
I still don't know the starter fail mechanism in play...commutator wasn't undercut correctly? Shorted turns? I just did not get the life from the starter motor I was expecting...I only got two years or so...I was expecting more like 30 or so.