Can capacitors be swapped to extend glow light and full glow cycle times?

Sixto
87 300D

I encountered a problem recently where the glow plug light seems to shut off after only a couple of seconds followed by a rather smokey and rough start. I checked the glow plugs and 1 of 6 had infinite resistance so I went ahead and ordered new ones. I should have them installed by the weekend. But now I'm wondering if its the relay or ignition switch. I noticed recently that every once in a while i would remove the key from the ignition and it would keep buzzing when I opened the door. I have to cycle the key again in order to stop it from buzzing. Could the ignition switch cause the glow plug relay not to function properly? Can a bad glow plug cause a short glow plug light?

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CENSORED due to not family friendly words

IIRC the glow relay has a function to detect and indicate two bad glow plugs but it can only detect faults in plugs 2 through 6, or something like that. The indicator is a glow light that continues after the engine is started. Some have mentioned a flashing glow indicator. Afterglow relays might have other diagnostic features. I'm sure OBD cars can identify a bad plug by cylinder number.

Sixto
87 300D

Thank you, I think thats whats happening in my case. The dead glow plug was #4, maybe theres others I failed to catch. I'll replace all 6.

I did a quick test just now where I unplugged the 6 pin glow plug output from the relay and tested the voltage on the relay output when I turned the key to position 2. When I turn the key the light goes ON and I get 12v continuously for about 30 sec (purple wire is snipped). So the relay seems to be functioning normally but it does detect an interrupted glow plug circuit and shuts off the light early. Maybe the trick to starting with one or more dead glow plugs is to keep the key in position 2 for 30 sec regardless of the light.

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CENSORED due to not family friendly words

sixto, the caps are 1/2 of the timing circuit. They do 'wear' out

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

Well guys, I know this was a long time coming, but I figured I would post an update. Thanks for all the help! I went ahead and upgraded to the newer afterglow relay and chose to replace the stock temperature sender with the updated one. It wasn't as hard as I thought...just had to be creative. I removed the injector lines for cylinders 4-6, and then used a crowfoot line-wrench socket to loosen the temp sender behind the injection pump. Popped the new one in and used new connectors for the new wire to make it look as stock as possible. I also changed my block heater because the old one had burned out.

The results were dramatic. Not only is the relay functioning properly again, but I have never experienced such smooth starts since I have owned the car (almost 2 years now). Without the block heater plugged in, it was 20 degrees out, I let the light cycle and waited about 5 seconds after the light shut off...she fired right up. No missing, excessive smoke, or anything. Makes me wonder how long the old relay had not been up to par!

Anyhow, thanks again...love this forum!

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97 S500 (90,000 miles) - wife's car
87 300D (298,000 miles and a replacement #14 head)
94 Suburban K2500 - need something to haul firewood
83 300SD (343,000 miles) (sold)