Glow Plug/gpr/hard Winter Start And White Smoke Thread
#31
11-08-2005, 07:06 PM
Fleet Owner
Originally Posted by badlands
Should both little wires be hot on the gpr when the key is turned on?My gpr one is hot <12 volt> with key off, turn key on one little is hot and the two big post are hot?Does this mean glow plugs are bad??
When you turn on the key, engine cold, you should see hot to both large terminals, hot to the forward small terminal, and nothing on the rear small one. (If my memory serves me correctly.) Once the engine has warmed up for a few minutes the ECU commands the glow plugs off and then you should see power to the large terminal leading in, the other large terminal should be out. The two small terminals will read full 12 volts. Again, the way that the ECU controls that relay is it completes the circuit to ground to turn on the relay. So you will always see power at both small terminals if the engine is fully warmed up and it is running. You will only see power to the other large terminal if the glow plugs are commanded on. And that will only be with a cold engine.
#33
11-09-2005, 08:00 AM
yep the front little wire hot until warm up then the other so its working correctly?So the only thing left is to change the glow plugs and valve cover gaskets or just keep plugging it in.I got an estimate on repair for all glow plugs and gaskets and labor was $1000.00 i think i will just plug it in for this year. thanks
#34
11-09-2005, 08:38 AM
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Originally Posted by badlands
yep the front little wire hot until warm up then the other so its working correctly?So the only thing left is to change the glow plugs and valve cover gaskets or just keep plugging it in.I got an estimate on repair for all glow plugs and gaskets and labor was $1000.00 i think i will just plug it in for this year. thanks
that is insaneeeeeeeeeeeeeeeeeeee....
glowplugs 9 bucks each at autozone.... 72 plus tax
vc gaskets 35 @ powerstrokeshopdotcom...70 bucks
uvc harnesses 25@ """" """ "" " " " "" .... 100 bucks
provided you need to replace those. at the most 250 bucks and a little of your time and some common hand tools you can do it yourself. its very very easy. even for someone with no wrench experience. you have found this site. now save your money and do all the work yourself. spend that 1000 bucks on some tools............
i doubt you even need all of those parts though. start checking things.
ohm your current plugs. check wiring harness plugs for burnt pins, check gpr, check uvcs if you get some bad readings.
vman your gpr is the smaller of the 2...
Last edited by 1997F-350; 11-09-2005 at 08:47 AM.
#35
11-09-2005, 08:43 AM
Here is a link to a document, I put together, on the glow plug relay...this is specifically for a 1999 7.3l, though I think the principles hold across all 7.3l. Hope this helps...
http://www.streamload.com/nlemerise/Ford/gpr.pdf
http://www.streamload.com/nlemerise/Ford/gpr.pdf
#36
11-09-2005, 10:31 AM
In another thread here, https://www.ford-trucks.com/forums/s...d.php?t=426789
I have attached a small photo of the glow plug relay, as seen from looking from the front of the truck.
Below is a reprint of my comments that reference that photo:
- - -
The large terminal on the left with a rubber boot over it goes directly to the batteries. It has +12 volts all the time.
The other large terminal, without a boot, is the switched +12 volts that is fed to the glow plugs when they are supposed to be on. That current gets fed to the glow plugs through the brown and yellow wires (below). I don't know where the blue wire goes. Anybody got those factory wiring diagrams?
The smaller terminal at the bottom has no voltage when the key is off, but gets +12 volts any time the key is on, engine running or not. It is the incoming current supply for the relay's coil.
The other smaller terminal, closer to the firewall, is the other side of the relay's coil. It is looking for a ground to activate the relay. When the key is first turned on, and glow plug heat is called for by the PCM (the engine computer), the PCM outputs a ground, thereby causing current to flow through the relay's coil, activating the relay, and sending current (at +12 volts) to the glow plugs. When glow plug heat is no longer called for, the ground that is output by the PCM goes "open", causing the relay to turn off. If you put a volt meter on this pin after the relay opens, you will see +12 volts here, too. Why? The wire in the relay's coil is feeding it to your volt meter.
If you short this terminal to ground through a switch, you can manually control the current to the glow plugs any time the key is on.
Since the winter weather is usually not that cold here in Southern California, I intend to install a switch inside the cab that opens the connection to this terminal. That will allow the timer to control the glow plugs normally ONLY when I want it to. Otherwise, when I don't need the glow plugs to be heated, I'll save myself the current drain on the batteries.
You could also wire a momentary-contact push button switch in the cab and have glow plugs only when you push the button, and complete manual control if you want it. I wouldn't use a toggle switch, as it could be forgotten and the glow plugs would be on all the time. Not a good thing.
Pop
I have attached a small photo of the glow plug relay, as seen from looking from the front of the truck.
Below is a reprint of my comments that reference that photo:
- - -
The large terminal on the left with a rubber boot over it goes directly to the batteries. It has +12 volts all the time.
The other large terminal, without a boot, is the switched +12 volts that is fed to the glow plugs when they are supposed to be on. That current gets fed to the glow plugs through the brown and yellow wires (below). I don't know where the blue wire goes. Anybody got those factory wiring diagrams?
The smaller terminal at the bottom has no voltage when the key is off, but gets +12 volts any time the key is on, engine running or not. It is the incoming current supply for the relay's coil.
The other smaller terminal, closer to the firewall, is the other side of the relay's coil. It is looking for a ground to activate the relay. When the key is first turned on, and glow plug heat is called for by the PCM (the engine computer), the PCM outputs a ground, thereby causing current to flow through the relay's coil, activating the relay, and sending current (at +12 volts) to the glow plugs. When glow plug heat is no longer called for, the ground that is output by the PCM goes "open", causing the relay to turn off. If you put a volt meter on this pin after the relay opens, you will see +12 volts here, too. Why? The wire in the relay's coil is feeding it to your volt meter.
If you short this terminal to ground through a switch, you can manually control the current to the glow plugs any time the key is on.
Since the winter weather is usually not that cold here in Southern California, I intend to install a switch inside the cab that opens the connection to this terminal. That will allow the timer to control the glow plugs normally ONLY when I want it to. Otherwise, when I don't need the glow plugs to be heated, I'll save myself the current drain on the batteries.
You could also wire a momentary-contact push button switch in the cab and have glow plugs only when you push the button, and complete manual control if you want it. I wouldn't use a toggle switch, as it could be forgotten and the glow plugs would be on all the time. Not a good thing.
Pop
#37
11-09-2005, 12:03 PM
SpringerPop...My reading of the glow plug system is that all of the following conditions MUST be me for the glow plugs to actually be energized by the system:
(1) the air temp must be below 55F degrees
Then if that conditon is met (<55F) there are two other conditions which are determined:
(2) the oil temp must be below 55F (If ABOVE 55F the PCM will light the "Wait to Start" light but will set the time to zero) and then
the atmospheric pressure is read
When the conditions (1 and 2) are met then the PCM determines the length of time that the glow plugs will be on from 0 seconds to 120 seconds (using the BARO sensor to assit in glow plug on time). What I find interesting, is that the "Wait to Start" light comes on IRREGARDLESS of whether the glow plugs are actually energized.
CORRECTION: If the air temp is below 55F degrees the glow plugs ARE energized, but using oil temp and barometric pressure the PCM determines what amount of time the glow plugs WILL be energized (0-120 seconds). IF the oil temp is below 55 then the time is automatically set to zero seconds by the PCM irregardless of the BARO sensor reading.
(1) the air temp must be below 55F degrees
Then if that conditon is met (<55F) there are two other conditions which are determined:
(2) the oil temp must be below 55F (If ABOVE 55F the PCM will light the "Wait to Start" light but will set the time to zero) and then
the atmospheric pressure is read
When the conditions (1 and 2) are met then the PCM determines the length of time that the glow plugs will be on from 0 seconds to 120 seconds (using the BARO sensor to assit in glow plug on time). What I find interesting, is that the "Wait to Start" light comes on IRREGARDLESS of whether the glow plugs are actually energized.
CORRECTION: If the air temp is below 55F degrees the glow plugs ARE energized, but using oil temp and barometric pressure the PCM determines what amount of time the glow plugs WILL be energized (0-120 seconds). IF the oil temp is below 55 then the time is automatically set to zero seconds by the PCM irregardless of the BARO sensor reading.
Last edited by nlemerise; 11-09-2005 at 12:27 PM.
#38
11-09-2005, 02:43 PM
nlemerise,
When I got out the DVM to do the testing I've written about, the engine was "at room temperature", and the air temperature was certainly above 55 degrees F. That makes me wonder if the ambient air temperature is really part of the equation.
I also have to wonder what atmospheric pressure has to do with it at all.
Of course, I can see if the engine's already warm, it doesn't need the glow plugs to start, hence the oil temperature sensing.
Your very last line above, however, doesn't make sense to me. It seems THAT is the condition when it DOES need glow plug assistance. Shouldn't that read "above"? Even then, I think the 55 is more like degrees C, not F.
Pop
When I got out the DVM to do the testing I've written about, the engine was "at room temperature", and the air temperature was certainly above 55 degrees F. That makes me wonder if the ambient air temperature is really part of the equation.
I also have to wonder what atmospheric pressure has to do with it at all.
Of course, I can see if the engine's already warm, it doesn't need the glow plugs to start, hence the oil temperature sensing.
Your very last line above, however, doesn't make sense to me. It seems THAT is the condition when it DOES need glow plug assistance. Shouldn't that read "above"? Even then, I think the 55 is more like degrees C, not F.
Pop
Last edited by SpringerPop; 11-09-2005 at 02:55 PM.
#40
11-09-2005, 07:04 PM
Originally Posted by SpringerPop
nlemerise,
When I got out the DVM to do the testing I've written about, the engine was "at room temperature", and the air temperature was certainly above 55 degrees F. That makes me wonder if the ambient air temperature is really part of the equation.
I also have to wonder what atmospheric pressure has to do with it at all.
Of course, I can see if the engine's already warm, it doesn't need the glow plugs to start, hence the oil temperature sensing.
Your very last line above, however, doesn't make sense to me. It seems THAT is the condition when it DOES need glow plug assistance. Shouldn't that read "above"? Even then, I think the 55 is more like degrees C, not F.
Pop
When I got out the DVM to do the testing I've written about, the engine was "at room temperature", and the air temperature was certainly above 55 degrees F. That makes me wonder if the ambient air temperature is really part of the equation.
I also have to wonder what atmospheric pressure has to do with it at all.
Of course, I can see if the engine's already warm, it doesn't need the glow plugs to start, hence the oil temperature sensing.
Your very last line above, however, doesn't make sense to me. It seems THAT is the condition when it DOES need glow plug assistance. Shouldn't that read "above"? Even then, I think the 55 is more like degrees C, not F.
Pop
! Youv'e got me on the issue of Barometric Pressure entering into the equation...I took the info from the 1999 7.3L cdrom...I haven't a clue...my kids could have told you that too 
!
#41
11-09-2005, 07:14 PM
#42
11-09-2005, 07:24 PM
Originally Posted by SpringerPop
Oh, I don't doubt YOU that those are really Ford's criteria for operation of the glow plugs, I just can't see FORD's logic for monitoring baro pressure as part of the equation.
Pop
Pop
...from DieselStop:<TABLE cellSpacing=2 cellPadding=3 border=0><TBODY><TR><TD vAlign=top align=left>BARO </TD><TD vAlign=top align=left>Barometric Pressure Sensor
Strategy input; PCM uses this to adjust fuel quantity and injection timing for optimum running and minimum smoke, also glow plug on time to aid starting at higher altitudes; 5 volts in, @ 4.6 volts/14.7 psi at sea level, decreasing as altitude increases.
</TD></TR></TBODY></TABLE>
#43
11-09-2005, 07:33 PM
So we should see longer glow plug time at higher altitudes? OKaaaaaay.
I'm still going to put a kill switch in mine. Before I do, however, I'm going to just take the small wire to the PCM off my GPR for the winter and see what happens. If it's got white smoke in the mornings, I'll put it back on. But in the meantime, I won't have that unnecessary high current drain from my batteries.
Pop
I'm still going to put a kill switch in mine. Before I do, however, I'm going to just take the small wire to the PCM off my GPR for the winter and see what happens. If it's got white smoke in the mornings, I'll put it back on. But in the meantime, I won't have that unnecessary high current drain from my batteries.
Pop
#44
11-09-2005, 07:51 PM
Fleet Owner
Originally Posted by SpringerPop
So we should see longer glow plug time at higher altitudes? OKaaaaaay.
I'm still going to put a kill switch in mine. Before I do, however, I'm going to just take the small wire to the PCM off my GPR for the winter and see what happens. If it's got white smoke in the mornings, I'll put it back on. But in the meantime, I won't have that unnecessary high current drain from my batteries.
Pop
I'm still going to put a kill switch in mine. Before I do, however, I'm going to just take the small wire to the PCM off my GPR for the winter and see what happens. If it's got white smoke in the mornings, I'll put it back on. But in the meantime, I won't have that unnecessary high current drain from my batteries.
Pop
#45
11-09-2005, 10:16 PM
Originally Posted by SpringerPop
So we should see longer glow plug time at higher altitudes? OKaaaaaay.
I'm still going to put a kill switch in mine. Before I do, however, I'm going to just take the small wire to the PCM off my GPR for the winter and see what happens. If it's got white smoke in the mornings, I'll put it back on. But in the meantime, I won't have that unnecessary high current drain from my batteries.
Pop
I'm still going to put a kill switch in mine. Before I do, however, I'm going to just take the small wire to the PCM off my GPR for the winter and see what happens. If it's got white smoke in the mornings, I'll put it back on. But in the meantime, I won't have that unnecessary high current drain from my batteries.
Pop