Let's Talk About Glow Plugs
Thread Starter
|
Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
Let's Talk About Glow Plugs
Winter's over and my starting problems are behind me (for now). Seeing as how important glow plugs seem to be to starting these things when it gets cold I'd like to have a full understanding of them, how they work and make sure mine are 100% next year. If better than OEM I'd be fine with that too.
Here's my understanding of how they work so we don't have to rehash what is known.
1) No glow plug no cold start.
2) GP, GPR and UVCH typical offenders.
3) GP's run for about 2 minutes after key on.
4) Full bank of lit GP's eats about 100 amps.
5) Ford GP's are highly recommended.
6) Ford GPR's are inferior and other relays should be used.
My GPR went south and I got new one and installed it. My truck would start sometimes, not others and sometimes with heavy fuel smoke. When I jumped the GPR with my screwdriver I could tell it was bad by the way the tip of my screwdriver glowed during the jump.
My initial questions:
1) How hot do the GP's get? Do they actually glow? Do they get hot enough to light the fuel? Does the fuel spray directly on them?
2) Do the GP's remain lit after the engine starts? If so for how long?
3) What does IH sell for GP's for use in their T444E?
4) I have found some Bosch GP's for these engines, any reports on those?
That'll get me started.
Thanks,
Mark
Here's my understanding of how they work so we don't have to rehash what is known.
1) No glow plug no cold start.
2) GP, GPR and UVCH typical offenders.
3) GP's run for about 2 minutes after key on.
4) Full bank of lit GP's eats about 100 amps.
5) Ford GP's are highly recommended.
6) Ford GPR's are inferior and other relays should be used.
My GPR went south and I got new one and installed it. My truck would start sometimes, not others and sometimes with heavy fuel smoke. When I jumped the GPR with my screwdriver I could tell it was bad by the way the tip of my screwdriver glowed during the jump.
My initial questions:
1) How hot do the GP's get? Do they actually glow? Do they get hot enough to light the fuel? Does the fuel spray directly on them?
2) Do the GP's remain lit after the engine starts? If so for how long?
3) What does IH sell for GP's for use in their T444E?
4) I have found some Bosch GP's for these engines, any reports on those?
That'll get me started.
Thanks,
Mark
Posting Guru
Joined: Oct 2008
Posts: 1,080
Likes: 10
1) No glow plug no cold start.
That's about it
2) GP, GPR and UVCH typical offenders.
Any resistance in the circuit will affect the overall operation.
3) GP's run for about 2 minutes after key on.
The On-Time is determined by the several sensors. The primary being the EOT. Glow Plugs will remain on a maximum of 120 Seconds. Cycling the Circuit as some suggest really does nothing unless you're waiting the 120 seconds.
4) Full bank of lit GP's eats about 100 amps.
Give or take, that's about right.
5) Ford GP's are highly recommended.
Anything other than OEM will give you problems. Maybe not the first year. But, thereafter its a crap shoot.
6) Ford GPR's are inferior and other relays should be used.
I wouldn't say "inferior". But, others like Stancore have better long lasting Solenoids.
My GPR went south and I got new one and installed it. My truck would start sometimes, not others and sometimes with heavy fuel smoke. When I jumped the GPR with my screwdriver I could tell it was bad by the way the tip of my screwdriver glowed during the jump.
The most probable reason the end of the screw drive is thinner thereby creating resistance.
My initial questions:
1) How hot do the GP's get? Do they actually glow? Do they get hot enough to light the fuel? Does the fuel spray directly on them?
Yes, the glow RED.
Fuel enters the cylinder Atomized. Allowing its combustion at a lower temperature. The heat, and compression of the cylinder both create an atmosphere which is conducent to combustion.
2) Do the GP's remain lit after the engine starts? If so for how long?
Up-to 120 Seconds. The Dash indicator turns off after only 6-12 Seconds.
3) What does IH sell for GP's for use in their T444E?
Their branded units. Which, I assume are the same as Motorcraft.
4) I have found some Bosch GP's for these engines, any reports on those?
See # 5 Above.
That'll get me started.
Thanks,
Mark
That's about it
2) GP, GPR and UVCH typical offenders.
Any resistance in the circuit will affect the overall operation.
3) GP's run for about 2 minutes after key on.
The On-Time is determined by the several sensors. The primary being the EOT. Glow Plugs will remain on a maximum of 120 Seconds. Cycling the Circuit as some suggest really does nothing unless you're waiting the 120 seconds.
4) Full bank of lit GP's eats about 100 amps.
Give or take, that's about right.
5) Ford GP's are highly recommended.
Anything other than OEM will give you problems. Maybe not the first year. But, thereafter its a crap shoot.
6) Ford GPR's are inferior and other relays should be used.
I wouldn't say "inferior". But, others like Stancore have better long lasting Solenoids.
My GPR went south and I got new one and installed it. My truck would start sometimes, not others and sometimes with heavy fuel smoke. When I jumped the GPR with my screwdriver I could tell it was bad by the way the tip of my screwdriver glowed during the jump.
The most probable reason the end of the screw drive is thinner thereby creating resistance.
My initial questions:
1) How hot do the GP's get? Do they actually glow? Do they get hot enough to light the fuel? Does the fuel spray directly on them?
Yes, the glow RED.
Fuel enters the cylinder Atomized. Allowing its combustion at a lower temperature. The heat, and compression of the cylinder both create an atmosphere which is conducent to combustion.
2) Do the GP's remain lit after the engine starts? If so for how long?
Up-to 120 Seconds. The Dash indicator turns off after only 6-12 Seconds.
3) What does IH sell for GP's for use in their T444E?
Their branded units. Which, I assume are the same as Motorcraft.
4) I have found some Bosch GP's for these engines, any reports on those?
See # 5 Above.
That'll get me started.
Thanks,
Mark
Here are some notes:
a. Glow Plug ON time is dependent on oil temperature and altitude. The Glow Plug relay comes on between 1 and 120 sec. and does not come on at all if oil temp is above 131 F.
b. Verify that B+ is being supplied on the large BK/W wire going to the Glow Plug relay.
c. Install a voltmeter to the glow plug feed terminal (two brown wires or center terminal on the shunt).
d. Using a Bi-Directional Scan Tool and EOT PID’s, verify glow plug "on" time.
e. Turn key to run position, measure voltage ("on “time) (Dependent on oil temperature and altitude) Relay on time Spec. Measurement 1 to 120 seconds B +
f. Note: Wait to Start Lamp "on" time (1 -10 sec.) is independent from Glow Plug "on" time
g. Glow Plug Resistance
h. Remove both 9 pin connectors from valve covers • Measure each Glow Plug resistance to Bat. Ground. Measure engine harness resistance to relay. .1 to 2 ohms
i. Glow Plug Connector to relay 0 to 1 ohms
Elder User
Joined: Jul 2009
Posts: 768
Likes: 1
From: Live VT, Work MA
The most important thing is to have the MINIMUM resistance feeding the Glow Plugs. Which means: Connections, Solenoid Resistance, Clean Terminals and the like. The rest is reliant upon starter condition and compression.
Here are some notes:
a. Glow Plug ON time is dependent on oil temperature and altitude. The Glow Plug relay comes on between 1 and 120 sec. and does not come on at all if oil temp is above 131 F.
b. Verify that B+ is being supplied on the large BK/W wire going to the Glow Plug relay.
c. Install a voltmeter to the glow plug feed terminal (two brown wires or center terminal on the shunt).
d. Using a Bi-Directional Scan Tool and EOT PID’s, verify glow plug "on" time.
e. Turn key to run position, measure voltage ("on “time) (Dependent on oil temperature and altitude) Relay on time Spec. Measurement 1 to 120 seconds B +
f. Note: Wait to Start Lamp "on" time (1 -10 sec.) is independent from Glow Plug "on" time
g. Glow Plug Resistance
h. Remove both 9 pin connectors from valve covers • Measure each Glow Plug resistance to Bat. Ground. Measure engine harness resistance to relay. .1 to 2 ohms
i. Glow Plug Connector to relay 0 to 1 ohms
Here are some notes:
a. Glow Plug ON time is dependent on oil temperature and altitude. The Glow Plug relay comes on between 1 and 120 sec. and does not come on at all if oil temp is above 131 F.
b. Verify that B+ is being supplied on the large BK/W wire going to the Glow Plug relay.
c. Install a voltmeter to the glow plug feed terminal (two brown wires or center terminal on the shunt).
d. Using a Bi-Directional Scan Tool and EOT PID’s, verify glow plug "on" time.
e. Turn key to run position, measure voltage ("on “time) (Dependent on oil temperature and altitude) Relay on time Spec. Measurement 1 to 120 seconds B +
f. Note: Wait to Start Lamp "on" time (1 -10 sec.) is independent from Glow Plug "on" time
g. Glow Plug Resistance
h. Remove both 9 pin connectors from valve covers • Measure each Glow Plug resistance to Bat. Ground. Measure engine harness resistance to relay. .1 to 2 ohms
i. Glow Plug Connector to relay 0 to 1 ohms
Thread Starter
|
Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
Yep, that told me that the relay was not working at that time. Next time I tried it I only got a little spark when I jumped it and that told me that the relay was working that time. Now she works, now she don't.
Trending Topics
Cargo Master
Joined: Nov 2005
Posts: 2,768
Likes: 58
From: East Tawas, MI
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Thread Starter
|
Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
I need to go flying. Bird gets annual inspection next week. Hadn't been up since August. Pulled it out Friday to see if it would start and it did. Sure is nice to have something with no battery drain when it's not turned on.
Senior User
Joined: Jul 2014
Posts: 112
Likes: 0
From: Denham Springs, La.
I did know that the glow plugs stayed on longer than the wait to start light because my gpr failed last year and I had a friend turn the key on while I was metering the relay. But what the heck does the light tell you to wait for then? Fuel pressure??
Also I don't have the LED mod. and I know I don't wait a full two minutes before starting. is this a bad thing? Should we be waiting for a full glow plug cycle before trying to crank when its cold? Could it do damage?
Also I don't have the LED mod. and I know I don't wait a full two minutes before starting. is this a bad thing? Should we be waiting for a full glow plug cycle before trying to crank when its cold? Could it do damage?
Thread Starter
|
Hotshot
Joined: Mar 2014
Posts: 10,750
Likes: 1,065
From: Douglassville, PA
Apparently there is no damage to glow plugs from starting while they are still glowing. Good question on the value of that ten second wait to start light. That is what made me ask if the glow plugs actually ignite the fuel.
Laughing Gas
Joined: Jan 2015
Posts: 820
Likes: 3
From: Central OK
Hey Walleye! I just swapped out my glowplugs and did a full writeup with pics in my build in my sig. Might be fun for a read. You can laugh at all my mistakes and skip those parts. They're not necessary for good glow plug workmanship anyway lol!
