Howdy from San Antonio,
I'm a new owner of a 90' f350 that won't start.
To test the glow plugs do you have to unplug them to use the test light test and if so do you just pull on the wire?
There seems to be a very brittle connector that sort of crummbled when I grabbed it.
Thanks

 

Yes, they do tend to crumble after a while. Just pull on what's left. You need to have them disconnected or you are testing them all at once. All you'll know is that at least one of them is working.

 

Thanks for the info.
I guess thats the first thing I'll check.
Kinda of a bummer just buying this truck.
It seemed like a good deal at $2500.
Nice straight rust free crew cab with good AC.
Oh well we'll just have to take this one step at a time.
Regards,
Dean

 

While you have the GP wire ends off get some heat shrink and cover the plastic ends or whats left...........

If you have 2 or more bad GPs, the controller may not cycle at all.

Two problems that occur with the solid state ( 1987 to 1994 IDI engines ) GP systems. If a GP burns out ( circuit resistance goes up ), the controller cycles the GPs at a faster rate which doesn't let them get to max operating temp. If 2 or more GPs fail, the controller may not cycle the GPs at all ( very rapid or no clicking heard ). When you check the GPs, use an ohmmeter. A high resistance ( not necessarily burned out ) GP can cause circuit resistance to go up and the controller will then cycle the GPs too fast. You probably will not find this problem with a test light. Resistance spec for GPs = .5 to 1 ohm cold. Second problem. A poor controller ground ( black wire attached to valve cover stud ) will cause the controller to leave the GPs on longer, often damaging or failing them. If you are having mulitple GP failures, I would check closely the controller ground. Now the confusing part. Bad ground --> longer GP on time ( slower cycling ). Burned out GPs --> faster cycling If you have both situations, it may appear that the controller is cycling the GPs at the proper rate. Bad ground slows it up while the burned GPs speed it up ---> normal cycling. The system acts/sounds like it's working normally, but you have a hard starting concern.
DieselDon

Glow plug torque is 12 ft lbs, I always use antisieze on the threads.

 

PLC7.3 ----- thanks for the tip regarding the never-seize ........ I hadn't really thought of that. My 7.3 has acted up in all three manners that you've described, analyzed and diagnosed.

Frogeye ----- 90 was a very good year for me ----- 220K so far and I wouldn't be afraid to head for 300K ........... but I've ordered a new one. However, I've had a buyer standing in line for the old one for several years ....... knowing what I have been able to do what I did with that truck! I've probably got 100K of that pulling my f/b trailer during work.............

 

I have checked the glow plug resistance and one was high at 80 ohms, all the rest were less than one ohm.
I removed the high resistance one, it says its a Champion.
Are these the correct brand?
The controller comes on initially for maybe 6 seconds then starts to click rapidly, perhaps every 2 seconds.
Should I replace just the bad one?

 

I have used both but I believe I get longer service out of the Autolite brand glow plugs. The quick cycling you describe is usually indicative of 2 or more plugs being bad. I would suggest removing them all and examining the tips for burn-out, soot build-up, etc. Sometime the soot is so burned on that the glow plug looses most of its usefulness.

 

throw those champions and autolights away, unless you want to have to pull the heads off to recover a broken gp tip someday, find a autozone, or IH dealer and get a set of Buero motorcraft glowplugs, maybe someone on here can get you ziggster's page on gp's to read. just my .02.

 

Looks like this might be the guy you reference, as I see an article regarding glowplugs!!

Thanks for the lead to the link ...................

http://www.members.shaw.ca/k2pilot/

 

OK, I installed 8 new glow plugs from the Ford dealer.
The thing just about jumped out of the truck when it started.
It warmed up to about 70 degrees today which was a big help.
I'm feeling better about this thing.
Thanks for all the information.
Time to work on the old Landcruiser and Husqvarna bike.