D30 novice looking to gain the mask of knowledge and enlightenment. Learning day by day. My Monster is an 86 D30 M1008 converted from 24v to 2 12v. What series of 12 v glow plugs should I be purchasing and from who?
When starting up in the mornings, glow light flash for 7/8 times. Won’t start. Leave and count 4/5 blink. Then I leave the key in starters for another 5 seconds works . Getting longer to start the truck in the morning. Do need new glow plug?
To simplify things and for you not having a clue on how old or the condition of the original plugs are. You should use a $7.00 test light probe "see attached" to check if you have any blown plugs.
Just clamp the alligator clip to the positive post of your battery and then touch the probe to the glow plug tab. If it lights up that plug is still good. No need to do all the work by removing the plugs and bench testing them "Sorry Rick". If you have just one bad plug you can
try replacing it with a new one. If you have 2 or more bad plugs you should replace them all. The old plugs over time build up a resistance in them and not burn as hot as new plugs. They will also take longer to heat the glow plug temp sensor which intern keeps the glow plugs burning longer and that can prematurely burn out any new plugs you installed .
13 G plugs are the original that GM used and work just fine. Some members suggest to stay away from the Wellman brand and nicknamed them Swellman for their issue of swelling and breaking. Other members including myself have used 60 G plugs "About $85.00 an 8 pack" but you have to replace the spade wire ends to a larger size to fit the 60s. I replaced mine in my 1009 in 2011 and they are still going strong.
Good luck