Okay so my new diesel ownership has hit the wall now.
I went out to my truck today and turned the key to "on", waited 10sec for the WTS light to go out and fired her up and she ran/drove great.
Came back home and turned it off/parked it.
About a half hour later I hop in my truck and turned the key "on" but the WTS light came on for around 3-4sec and I heard the dreaded clicking.
I've done enough reading here that I knew some of my glow plugs were bad, so I ran down to napa and bought 8 new autolite glow plugs and installed 7 (except for the 1 under the turbo on the drivers side).
I hooked the batteries back up temporarily and turned the key "on" and the WTS came on for 10sec, no clicking.
So I figured "awesome, I fixed it!" I disconnected the batteries and reassembled the truck.
After I was done,
I jumped in the truck and fired her up and she ran/drove great again.
When I got home I turned the truck off/parked it.
I went back out 30mins later turned the key on and the WTS comes on for around 6secs and I crank the truck but she cranks over slow with kind of a "whine" and won't fire up,
Is it REALLY that last glow plug that's the problem????
Or is it something else I'm missing?
The battery light is lit on my dash and the "water in fuel" light will faintly flash once or twice during cranking but won't stay lit-up.
I'm going to replace that last glow plug tomm but I'm not sure if that's the issue(?)
Any input would be great.

 

glow plugs wont make the truck turn over slower, that's batteries, starter, and cable stuff. it is the time of year for batteries to start dying. I lost three interstates last month. I'm not buying any more of them.

 

what year is your truck? what your describing is proper glow plug operation of the 1987-1994 GP system and by the sounds of it,you needlessly replaced properly functioning glow plugs (with inferior ones.) did the gp's you removed say "BERU" on them? if so.put those ones back in.by your cold start description,they're good.

with a warm engine like those times it didn't want to start,the glow plugs were not needed.
it sounds like your batteries,cables or the starter is dieing like red says.the engine should turn over super strong and quick,hot or cold.

 

True, I was cranking on my truck so I'm sure they're low and I've placed them on a deep cycle charger now, batteries were both replaced 1000ca's each.
I'm more concerned about the "no-start" and if my last glow plug suddenly went bad between my other glow plug replacements and the test drive.
Sorry I should've included more info, it's an 87 so ill check my batteries, starter, etc I didn't realize my GP's were functioning correctly, I thought since the WTS light only came on for 3secs and the clicking that some of my GP's were bad (?)
The GP's I took out said autolite also

 

I've burn auto lights out before by just replacing 7 they aren't very good glow plugs. just unhook the glow plugs and give it a little sniff of starting fluid until you can get Motorcraft plugs or bosh in it.

 

that would be bad if the engine was cold.since it was warm the glow plug controller limits glow time (if the engine is very warm right down to just a light flicker) down to just what is needed for glow time.generally,during spring/summer you don't even need to wait for the light after the first start of the day.just touch the key and she'll run.
now that's it's fall,you'll notice the truck will start hard if you left it sitting for a couple hours again if you don't wait for the light.
since yours is hard starting when warm it could mean your ip is on it's way out...........however you stated something else of great importance to help diagnose the issue; slow cranking.
so it's possible the starter is getting heat soaked or the alternator may not be changing the batteries,or the batteries are on their way out.

 

Dang I grabbed the wrong gp's, I meant to get motorcraft instead of autolite,
Which are good gp's?
-Bosch (I've heard they're plugs are bad but how are their gp's?)
-Champion (I don't normally use their products bad experiances.)
-Delphi (almost $20 per gp seems pricey (?))
-AC?
-Echlin ? (napa brand)

Oddly enough, I thought about heat soak of the starter as well, because the starter was slow cranking with a slight "whine" from it BUT only after it was warmed up, it started fine once the truck was "cool", or had sat for a certain length of time (I.e. Like my initial start up of the day and then after it sat for a good amount of time when I changed GP's)
If it starts right up tomm then won't restart after its warm that should give me confirmation that starter needs replaced...
Thanks a bunch guys, it's awesome having a group of knowledgeable people that know their stuff to use as a sounding board!
I'll update tomm with info

 

slow cranking will cause no starts, ALL 6.9-7.3 starters are gear reduction type starters, two basic designs are available up to 4 kilowatt, they the shorter external gear type are much easier to install and claim to spin up to 50 rpm faster for easier starts. I bought the no nose cone design one at Orielys 3.4 kilowatt spins real fast. your gp controller needs feed back type glows to function correctly Zd9's are the best.

 

get those autocrap plugs out of there before they cause you any more problems. you want only motorcraft /beru plugs.
either ZD-1, or ZD-9, depending on the style controler you have.
for the old style spade style plug it is the ZD-1. the new style bullet connector is the ZD-9
you can buy both styles from rock auto for under $10 each.
here is the link for the ZD-9: MOTORCRAFT Part # ZD9

and this is for the ZD-1: RockAuto Parts Catalog

 

Great minds think alike! I'm looking for zd9's now that are in-stock and near-by (new style controller bullet connectors 87-^ mines an 87) I meant to get motorcrafts instead of autolites I always get the 2 confused because years ago I associated autolite with ford products, AC with GM etc etc.
I went out this a.m. And the batteries were at 100% and I disconnected the charger, turned the key "on", WTS light came on for 10secs, I cranked her up and she hit and fired right-up and ran like a dream, so replacing the starter is on my list of tasks today.
On a positive note,
When I was reassembling the truck yesterday I found an unplugged connector and I plugged it back in and now my stock oil pressure gauge works (as does the aftermarket unit) and my "check engine" light is off. So I "accidentally" fixed something lol.
Now for the rear antilock brake light.....

 

what is the battery voltage w/ the engine off?

 

for spark plugs, autolite or motorcraft copper core are the best for ford.
but for glow plugs, the autolites suck. i have seem more burn out withing 10 start cycles than i have seen work for 1 year.

 

12v according to my tester/starter charger, but I need to put multimeter on them.
Ok Put my meter on them:
12.68v off (from both batteries)
13.5v at idle (both batteries)

 

That's plenty of juice. Someone else mentioned cables. How do your cables and grounds look?

 

Cables don't look fantastic BUT they don't look bad either (I've seen worse, by a lot lol) there's no heat generating in the cable (resistance) so internally I'm assuming they're at least okay.

I'm stumped here guys,
I've worked this truck hard, off/on and I've turned it off and started it probably 30-40 times (or more) all day today, and she has fired and ran great, every single time, she's not even cranking slowly or cranking excessively, she just fires and runs great (I'm not complaining lol) but I'm trying to recreate the issue and it's not happening...
I did go thru and soak my grounds and cable ends and connectors in wd40 then wiped them off or hit em with a wire brush (half ***) but maybe I broke something loose/clean????
I'll keep running her and see if I can get her to act up...