Glow Plug relay tested - what are correct voltages?

[Flinch]

Early '99, hard starting in 30-40 degree weather. Much worse than last year. Takes from 2 to 5 tries, then white smoke and rough idle for 30 seconds, then runs OK.

Tried turning on key, waiting, then off...then on/off several times- no difference.

Measured batteries with neg cable detached: 12.7 volts each. Two weeks ago when Ford put in new tranny (don't ask) they said batteries tested low: I think 27% and 60%. But I am hesitant to trust, since they had a large battery 'for sale' display...but maybe batteries?

Turned on key and measured glow plug relay voltages:
Large open stud: 12v. Small post nearest front: 12v. Small post to rear: .6v (yep, point 6). Fourth stud is covered and is +v feed. After about a minute the .6v stud 'came alive', and went up to nearly 12v. I heard a click when it happened.

Are these correct voltages?

I also checked the battery connections - tight and clean. The injector sump has correct amount of oil.

So, is the relay acting normal? If so, where to look next?

Am on days off until Wed, so need to fix truck soon. Unfortunately, where I park while working is out of town (motel) and can't plug in the block heater - drat!

Thanks guys!

Flinch

Early '99, DP Tunes, GV Overdrive (and YES, it gives from 15-25% better fuel mileage - yippeee!!)

[NCHornet]

First of all test the batteries during cranking. Keep pos and neg cables on and with your mulimeter lead on each post have someone crank engine. Just sitting should be around 12,6 volts, if it drops below 11 volts while cranking your batteries are weak and need replacing. For testing the GP system I have a tech write up in the maintenance section, but when the key is turned on you should here a loud click and you should have 12 volts at both large studs, the rear may be 11 volts but that's okay!! If you don't you have a bad GPR and it needs replacing. For a stock replacement use the GPR #109 from Napa, you will have to rotate it 180 degrees to mount but the wires fit fine. It is less than half the GPR 110 that Napa's book says is for our trucks. The best replacement is the heavy duty Stancor replacement!! It's what I suggest everyone to use!!
If all this checks out you need to ohm test each gp.

NCH

[Flinch]

I get +12v on both large studs, but the question is what about the two small ones? I get +12v on the front small, and .6 volts on the rear small one.

Do BOTH small studs feed the glow plugs? If so then it seems that the rear small stud is not getting proper voltage.

Wish I had a wiring diagram.

Thanks for reply!

Flinch

[NCHornet]

No you sound fine, now you need to ohm the UVC harness to see if your GP's are good. Look at my article under the maintenance section.

NCH

[NCHornet]

Here you go

Troubleshooting GPR & GP's

[Flinch]

Replaced four GPs and she starts great.

Thanks for the help

Flinch

[NCHornet]

Glad I could help!!

NCH