What is the best way to check glow plug function to find the bad ones? The solenoid is new and the "wait to start" light stays on for about 15 seconds. This is on a '95 Power Stroke, 196k miles. Thanks Kyle.
Clip the test light onto the postive,yes battery positive terminal.Then disconnect the glow plug,and touch the test light to the glow plug.It should light up.If it doesn't,then that one os bad.Repeat for all 8 plugs.
If one is bad,I recommend replacing them as a set,they will work better,and last longer that way.
When removing,if they don't want to come out easy,be careful.Slowly pull straight up and twist gently.Some throttle body cleaner sprayed down the hole will help loosen up carbon and get it out easier if it's stuck.Do not rock them side to side,or they it will break them off (see below)
Use liberal amounts of anti-seize on the threads,and don't overtighten.
ONLY USE MOTORCRAFT OR BERU glow plugs.
The other types balloon when they burn out,and break off when removing.This will damage the engine if unnoticed,and requires head removal to get them out.
Just before Christmas, I had 2 glow plugs on my 6.9 go out on me. Tested to see which ones were bad with 12 volt test light. I went to parts store, they were out of Champions glow plugs, but, did have in stock, right here, right now, Autolite. Needless to say, I took all they had, (4) and replaced the bad ones. Just this past Tuesday, I was replacing the 2 burnt out Autolites....pure junk. The ends ballooned out making removal a real enjoyable experience, similar to a root canal without novacain. In the end, I and the new Champion glow plugs won but, not after some fretting about having a piece of plug drop down the chamber. The Champions are what I have used since day one. They are more than double the price of the Autolites off the shelf, but, spending an entire day before a snow event changing out burnt plugs is just too much fun to put a price to. I don't think Autolites are going in my truck again until I part with it. (which I don't plan on very soon!!!!)