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7.3 Glow Plug Relay Cycle Time Depends On Oil Temperature

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7.3 Glow Plug Relay Cycle Time Depends On Oil Temperature

 
  #1  
Old 01-31-2019, 10:09 AM
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7.3 Glow Plug Relay Cycle Time Depends On Oil Temperature

Hey all, I thought I'd create this post as too many times I read misinformation regarding how the glow plug relay (GPR) functions re: cycle time. For the record, the "Wait To Start" light does not monitor the actual GPR cycle time. The length of the GPR cycle time is determined by the oil temperature (in Fahrenheit) and is controlled by the PCM. The chart below shows how long the GPR activates the glow plugs depending on the temperature of the oil. In other words, the colder your oil is ... the longer the GPR will stay on up to approximately 120 seconds (2 full minutes).

Before I bought a cheap digital voltmeter to plug into my lighter socket to watch the current/volts drop when the GPR was cycling, I used to watch the dash voltmeter needle move when the GPR was activated and deactivated. And yes, in cold temps with a cold engine (we're currently experiencing -10*F ambient temps where I live), my truck takes up to the full 120 seconds for the GPR to complete one full cycle. In fact, in these really cold temps and after the truck has been sitting outside all night, I will cycle the glow plugs a full 2 or even 3 times before starting my truck. And yes, I plug in my block heater and I have a battery blanket on each of my two batteries. So far ... so good. Hopefully the accompanying chart will help other 1999-2003, 7.3 owners.

 
  #2  
Old 01-31-2019, 10:58 AM
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Yep, that puppy has one good timer built into it too, when I time it it hits right on 120 seconds.
 
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Old 02-08-2019, 08:29 PM
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glow plug relay

f350 7.3
I was going to replace the gpr on this truck the one you here click gets hot so it is shorted out , but there is another relay to the side of this one , what does it do
 
  #4  
Old 02-08-2019, 08:48 PM
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Originally Posted by mac27041 View Post
f350 7.3
I was going to replace the gpr on this truck the one you here click gets hot so it is shorted out , but there is another relay to the side of this one , what does it do
Intake air heater. It is the same as the relay that is used for the GPR.
 
  #5  
Old 02-08-2019, 10:19 PM
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Pittsburgh can get pretty cold. I typically can get the full 2 minutes out of the plugs if we're at our coldest temps. Here's what I want to know though, are the battery blankets gimmicks or what? Plenty of people on here mentioning them, I just don't see how the non-powered ones could make a difference.
 
  #6  
Old 02-08-2019, 10:49 PM
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Originally Posted by burnthelight88 View Post
Pittsburgh can get pretty cold. I typically can get the full 2 minutes out of the plugs if we're at our coldest temps. Here's what I want to know though, are the battery blankets gimmicks or what? Plenty of people on here mentioning them, I just don't see how the non-powered ones could make a difference.
The non-powered battery blankets that come stock are there to protect against underhood heat in the summer.
The powered battery blankets do help quit a bit. One thing that makes a huge difference is a 50 watt oil pan heater. https://www.etrailer.com/Vehicle-Heaters/Kats-Heaters/KH24050.html
Even though it's only 50 watts, your truck will crank like a summer day.
 
  #7  
Old 02-09-2019, 10:10 AM
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Originally Posted by HD Rider View Post
The non-powered battery blankets that come stock are there to protect against underhood heat in the summer.
The powered battery blankets do help quit a bit. One thing that makes a huge difference is a 50 watt oil pan heater. https://www.etrailer.com/Vehicle-Hea...s/KH24050.html Even though it's only 50 watts, your truck will crank like a summer day.
HDRider, thanks for explaining what that torn up, ratty wrap around my old battery was. I didn't see a power cord when I stripped it out (actually it disintegrated on me) and was wondering ... what purpose did it serve. The two Temro 80w battery blankets I installed this past November seem to be doing a good job. Now that my block heater is working as it should, my truck, which is parked outside all of the time, starts up in 12*F temps like its summer and 80*F.

 
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Old 02-09-2019, 10:12 PM
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Dumb question......possibly:)

Would a light bulb , under the hood, help with the frigid temps. Trying to work with what I have lol
 
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Old 02-09-2019, 10:51 PM
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Any heat source will help.
I used to start engines in sub zero temps by heating the air intakes with a small torch or even a hair dryer.
 

Last edited by HD Rider; 02-09-2019 at 10:54 PM. Reason: Add
  #10  
Old 02-10-2019, 03:01 AM
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Originally Posted by LittleLucy View Post
Would a light bulb , under the hood, help with the frigid temps. Trying to work with what I have lol
Yup. The factory block heater is supposedly rated at 1000W, mine pulls 860-ish, so consider that when you're sizing a light bulb to serve as your block heater.
 
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Old 02-10-2019, 09:50 AM
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Originally Posted by LittleLucy View Post
Would a light bulb , under the hood, help with the frigid temps. Trying to work with what I have lol
A light bulb should help. Some farmers use incandescent bulbs to keep a little heat in their shallow well pump sheds to keep the water from freezing in the lines. I'd just be careful where I'd position it ... i.e. not directly touching anything that has oil or grease on it. Don't want to encourage all that extra "heat" from setting something on fire.
 
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Old 02-10-2019, 10:51 AM
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Originally Posted by sunuvabug View Post
A light bulb should help. Some farmers use incandescent bulbs to keep a little heat in their shallow well pump sheds to keep the water from freezing in the lines. I'd just be careful where I'd position it ... i.e. not directly touching anything that has oil or grease on it. Don't want to encourage all that extra "heat" from setting something on fire.
This is a good point. A children's easy bake oven operates at up to 400* and is heated by a lightbulb.
 
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Old 02-10-2019, 04:33 PM
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Thank you :)

I don't think my block heater works
 
  #14  
Old 02-10-2019, 05:42 PM
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I would start by checking the cord to your block heater. That's the part that most often fails.
The heater is located in the oil filter housing. The cord is retained by a threaded lock collar. You can unscrew the lock and unplug the cord to change it. To replace the heater itself, it's best to drain the cooling system or you'll get a shower under the truck. Cords and heaters are sold separately.
 

Last edited by HD Rider; 02-10-2019 at 05:43 PM. Reason: Spelling
  #15  
Old 02-10-2019, 06:44 PM
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Cold natured b#*@#

I am so tired of the effort that I have to go to to get it started if I don't drive it everyday
I had a conversation with it that went like this
"ok....so I have you for times like this (snowpocalypse in Seattle ish) and you don't wanna start in times LIKE THIS!!!!!
GGRRRRRR
I literally had a girl tantrum
I got close
it vrrmed for a half a second
but we're in unusual conditions
the conditions where I really need this b..... to RUN
I look after a vet and an elderly woman
sorry
just venting
thanks for the input
and I do believe that the light bulb helped somewhat
 

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