# 7.3 cold weather start



## Snowaway

Hello I have a 02 3/4 ton with a 7.3 diesil. This is my first winter with this truck, I was hoping you guys could tell me about starting in cold weather. Where I live it would be difficult to plug the block heater in. How cold can it get before it won't start? It never gets much below 10 degrees here, without the wind chill. Thoughts.


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## cretebaby

Snowaway;641548 said:


> Hello I have a 02 3/4 ton with a 7.3 diesil. This is my first winter with this truck, I was hoping you guys could tell me about starting in cold weather. Where I live it would be difficult to plug the block heater in. How cold can it get before it won't start? It never gets much below 10 degrees here, without the wind chill. Thoughts.


when my 02 was new i never pluggged it in for the first 3 years ad it gets well below zero here BTW wind chill wont have any effect on it

but in reality if your glow plugs arnt perfect i would get a little nervous at 10 degrees if you have to get it started


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## Ford445

Some trucks are more tempermental then others. We have all diesels, 7.3, 6.0 and 6,4. Our 7.3s seem to start harder in the cold. We have a couple that if they arent plugged in under 20 degrees they dont want to start, others will start anytime. I personally plug mine in if it is going to be sub zero. Im sure you will get a lot of different opinions, but thats mine.

:salute:


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## Doakster

Snowaway;641548 said:


> Hello I have a 02 3/4 ton with a 7.3 diesil. This is my first winter with this truck, I was hoping you guys could tell me about starting in cold weather. Where I live it would be difficult to plug the block heater in. How cold can it get before it won't start? It never gets much below 10 degrees here, without the wind chill. Thoughts.


A proper running 7.3 with a proper functioning glow plug system will start with no problem down to 0 degrees. I've done this many times because I didn't have a place to plug my truck in last year either.

-10 Degrees with out block heater assistance is also feasible but a stretch.


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## Case580M

Snowaway;641548 said:


> Hello I have a 02 3/4 ton with a 7.3 diesil. This is my first winter with this truck, I was hoping you guys could tell me about starting in cold weather. Where I live it would be difficult to plug the block heater in. How cold can it get before it won't start? It never gets much below 10 degrees here, without the wind chill. Thoughts.


Snowaway, Thats what I drive a '02 7.3L.










as someone said if the glow plugs are working properly you should not have an issue to around -10. I did have an issue and it turned out to be the Air Charge temp sensor instead of the normal glow plug issue. Weird I know but that was it.

This is my 3rd 7.3L and a year or so ago was in Minnesota when it was -27 and truck without being plugged in started but not so easy. (my heater was not working)

Keep it in top shape and you should not have issues. Another tip is before you retire for the night let it run up to operating temps then start it early in the morning when you wake up. Seems to get worse if you let them sit for extended periods

Now I cheat and just park it in the heated shop. early morning jump in and its already 70deg..... no scraping or waiting just go


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## Vinnie

Mine is a 2002 also . Anything under 20 degrees is a gamble with mine if its not plugged in . Glow plugs work ,fuel filter always changed before cold weather starts and still a stubborn truck.i actually looked into a webasto coolant heater .


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## jayw

Running a 10 weight synthic oil also seems to help with the cold starts as well


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## brad96z28

My 97 powerstroke always started with ease even on the coldest days. I never ever had to plug it in.


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## Doakster

jayw;642683 said:


> Running a 10 weight synthic oil also seems to help with the cold starts as well


Agreed, I run Rotella Synthetic 5W-40 and it was a night and day difference of cold cranking speed and start up, engine also runs a little smoother.


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## Doakster

Vinnie;642553 said:


> Mine is a 2002 also . Anything under 20 degrees is a gamble with mine if its not plugged in . Glow plugs work ,fuel filter always changed before cold weather starts and still a stubborn truck.i actually looked into a webasto coolant heater .


Are you sure that you're GP system is functioning properly. Have you checked the resistance at each of the GPs and function of GP relay?

As stated you should not have a problem at 20 degrees or lower.


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## sglaine

Snowaway;641548 said:


> Hello I have a 02 3/4 ton with a 7.3 diesil. This is my first winter with this truck, I was hoping you guys could tell me about starting in cold weather. Where I live it would be difficult to plug the block heater in. How cold can it get before it won't start? It never gets much below 10 degrees here, without the wind chill. Thoughts.


I have a 2000 F-350 and never had to plug in .

except 10 or below..How ever I do cycle the glow plugs twice before starting..


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## Mark Oomkes

Doakster;641565 said:


> A proper running 7.3 with a proper functioning glow plug system will start with no problem down to 0 degrees. I've done this many times because I didn't have a place to plug my truck in last year either.
> 
> -10 Degrees with out block heater assistance is also feasible but a stretch.





Doakster;642734 said:


> Agreed, I run Rotella Synthetic 5W-40 and it was a night and day difference of cold cranking speed and start up, engine also runs a little smoother.


Doakster pretty much beat me to it all.

What he said. Make sure you're running some fuel treatment to so as to prevent fuel gelling up on you.


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## jdo150

yeah our 7.3 starts hard in the cold.... I mean it will start but it takes a min to get it going and ours sits most of the winter and only gets moved when we plow the drive but when we plug the truck in it fires right up no problem and as far as our 6.0 im not to sure as it sits in a garage all night but when we have had it sitting out all day in the cold there has never been a problem.


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## Stud Bro

i have a 99 7.3 i had issues with it starting hard replaced the glow plug relay and 2 new batts and the truck pops right off I didnt plug the truck in at all last year on the really cold morning i cycle the plugs twice just run some cetain boost and the truck will be fine.


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## cretebaby

Doakster;642745 said:


> Are you sure that you're GP system is functioning properly. Have you checked the resistance at each of the GPs and function of GP relay?
> 
> As stated you should not have a problem at 20 degrees or lower.


if your that far into it you would be best off to just replace the glow plugs since they are fairly cheap


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## brad96z28

cretebaby;643673 said:


> if your that far into it you would be best off to just replace the glow plugs since they are fairly cheap


Yes but the cover gaskets and harnesses are not. It all adds up. It takes all of 2 min to ck them at that valve cover connectors.


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## Doakster

brad96z28;643924 said:


> Yes but the cover gaskets and harnesses are not. It all adds up. It takes all of 2 min to ck them at that valve cover connectors.


Exactly correct.



cretebaby;643673 said:


> if your that far into it you would be best off to just replace the glow plugs since they are fairly cheap


The GPs used to be cheap but not any more, a complete set will run & 80-100, and as stated it doesn't take much to check the plugs and you don't have to remove the valve cover.

I actually picked up a set of ZD-11s when autozone depleted there entire stock for 1 cent, yes 1 cent each. I think I paid 9 cents total for a set of 8 with tax. Now if I could just remember were I put them in case I need them.


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## brad96z28

This is where I purchased all my glow plug parts. And other motorcraft stuff as well. They where a ton cheaper then the dealer and the shipping was fast.
https://k-mansparts.storesecured.com/items/super-duty/7-3-diesel/glow-plug-related-items/list.htm


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## gotsnow?

my '00 F-250 starts hard below 30....... I may have glow plug issues though :crying: I just don't want to spend the money, it's easier to plug it in at night.

David - got snow?


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## brad96z28

Could just be the relay they go bad often. Only like a 50 dollar part. Takes all of 2 min to change also.


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## Doakster

Stud Bro;643489 said:


> i have a 99 7.3 i had issues with it starting hard replaced the glow plug relay and 2 new batts and the truck pops right off I didnt plug the truck in at all last year on the really cold morning i cycle the plugs twice just run some cetain boost and the truck will be fine.


You do not need to cycle the glow plugs twice on a 7.3, this does not give you any advantage.

This is because after the glow plug light goes out the GP plugs remain on for a time period that is decided by the PCM (computer). The glow plugs actually continue to cycle on after the engine has started as well.

The AIH (air intake heater) is also usually running during this time period. The AIH is located in the turbo Y-manifold, it is a small coil type heater that aids in heating the intake air going into the motor, it does not aid in cold starting but helps after the motor has started for easier running and warm up. The AIH also is fired off a relay system on ALL 7.3s.

GP and AIH functions and cycling are based on engine operating temp.

The glow plug light or wait to start light is merely an idiot light to tell the operator/driver to wait for a bit to start the truck, and is not related to when the glow plugs cycle off. Notice how the light will remain on for a longer or short time period based on if the engine is cold or not, this is the PCM controlling the light and telling the driver to wait for a bit.

A GP system that does not involve the PCM and simply relay/GP on/off would benefit from cycling twice.

I can't emphasize the simple fact that if the GP system is FULLY operational a 7.3 will fire in 0 degrees or less with no problem or doing anything "special".

Some other key factors in a 7.3 firing during cold temps are battery power and a running a lighter weight oil (5W-40). Good battery power and a lighter weight oil will both help in fast cranking speeds.....the major factor in getting any diesel to fire.


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## cretebaby

why wouldnt the intake heater help with cold starting?


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## Doakster

cretebaby;645237 said:


> why wouldnt the intake heater help with cold starting?


It has very little aid in starting. Think of it this way.

The GPs are located within the cylinder and directly aid in firing the fuel.

While the AIH is locate way down stream and will heat a very minimal air volume when cranking the engine compared to the GPs. It has much less heating ability than the GPs. Make sense?

Many people don't realize that they have a bad AIH or bad AIH relay but their truck will still start perfectly in the cold


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## earnies2

*Proper maintaince*

I have a 97 7.3 and every fall i change the glow plugs and the GPR and I never have a problem starting................I also cycle the glow plugs 2 times before i crank the engine....last year i went up to NH to repair a loader and ended up staying overnight and it was below 0 and i was going to plug her in and forgot.....thought i was in trouble in the morning it was 12 below and she fired up even I was surprised .....replace the GP'S and the GPR it's the best insurance you can buy.......This year i'm changing to a stancore relay....


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## Doakster

earnies2;646606 said:


> *I have a 97 7.3 and every fall i change the glow plugs and the GPR and I never have a problem starting................I also cycle the glow plugs 2 times before i crank the engine..*..last year i went up to NH to repair a loader and ended up staying overnight and it was below 0 and i was going to plug her in and forgot.....thought i was in trouble in the morning it was 12 below and she fired up even I was surprised .....replace the GP'S and the GPR it's the best insurance you can buy.......This year i'm changing to a stancore relay....


Wow I guess it is like buying insurance....but why take the time and money to do all that if it is not needed. GPs and GP relays just don't go bad every year, it would take less time to check you're GPs and GP relay to see it they are good than replace them, plus a lot less money. To each his own though.

I agree on switching a stancore relay, although I hope you're not going to switch that out every year, that big beast will last forever.


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## Ggg6

Doakster I would say the AIH does help cold starts. The AIH is not located way downstream, it is immediately before the intake plenum's. So the air only has a rather short path to the cylinder after being heated by the AIH. About the same distance the Cummins B and C engines have after the intake grid heater, and they do not use GP's.


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## Doakster

Ggg6;646895 said:


> Doakster I would say the AIH does help cold starts. The AIH is not located way downstream, it is immediately before the intake plenum's. So the air only has a rather short path to the cylinder after being heated by the AIH. About the same distance the Cummins B and C engines have after the intake grid heater, and they do not use GP's.


Right....but how much of an air charge is heated by the AIH during the INITIAL cranking, not much compared to the glow plugs. The glow plugs are the main factor in start assistance not the AIH. By down steam I meant that it is no where near the cylinder and fuel during initial cranking compared to the glow plugs, that's what you really care about.

If the AIH is not functioning 9 times out of 10 the truck will fire when the GPs are good. But take out 2-3 glow plugs and then you start having trouble.

My main point is that it does not have anywhere near the heating capacity of the GPs and is not a major factor in initial fire of the motor . It may help slightly however.


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## Ggg6

I'll agree with that statement in general, I thought you were saying it had no effect at all.


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## earnies2

*Everything has a price*

The reason i change the GP and GPR every year rather than test them is tha simple fact of dependiballity when i turn the key I need them to work and it is a small price to pay for that.....If you test them and thay test good today thay might fail tomorrow or even worse whean you need them to perform.......Plus i uasually never plug her in so what do you think i'm saving in electricty.........payup


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## dellwas

Mine's a '97 7.3L. Mine is okay till about -5C, here in Nova Scotia. Anything cooler and I plug in the block heater with a timer. I set it to shut off a couple of hours before I'm ready to go. Starts right up every time, no matter how cold it gets in those 2 hours.


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## cjcocn

It hasn't gotten cold here yet, but we did have a day or two of -19C (-2F) and my '00 7.3 fired up. It romped for a few seconds, but it fired up. Just to be on the safe side I waited an additional 30 seconds or so after the Wait To Start (WTS) light went off.

During the winter when it's really cold and I've forgotten to plug it in, I can sometimes get it to start by waiting up to 1 1/2 minutes after the WTS light goes off.

If it gets to -40 with a serious wind chill, I'll put a tarp over the hood to cover the front and keep the wind off of it. If I do not, then I risk having it not start even if it is plugged in.


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## Doakster

cjcocn;649246 said:


> It hasn't gotten cold here yet, but we did have a day or two of -19C (-2F) and my '00 7.3 fired up. It romped for a few seconds, but it fired up. Just to be on the safe side I waited an additional 30 seconds or so after the Wait To Start (WTS) light went off.
> 
> During the winter when it's really cold and I've forgotten to plug it in, I can sometimes get it to start by waiting up to 1 1/2 minutes after the WTS light goes off.
> 
> If it gets to -40 with a serious wind chill, I'll put a tarp over the hood to cover the front and keep the wind off of it. If I do not, then I risk having it not start even if it is plugged in.


That is a prefect example of the glow plugs remaining on after the WTS or GP light goes out just as they are designed.


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## brad96z28

Doakster;649251 said:


> That is a prefect example of the glow plugs remaining on after the WTS or GP light goes out just as they are designed.


Easy to tell when the gp relay kicks off just watch ur volt meter. 200 amps is very noticable on ur voltage guage It usually jumps up from 12v to 14v after about 2 min.


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## sno&go

jayw;642683 said:


> Running a 10 weight synthic oil also seems to help with the cold starts as well


DING DING DING!!!! Synthetic oil will help a lot in cold weather. I've used Amsoil in my 1999 super duty and I can fire that thing up without being plugged in at 10 degrees.


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## brad96z28

sno&go;651520 said:


> DING DING DING!!!! Synthetic oil will help a lot in cold weather. I've used Amsoil in my 1999 super duty and I can fire that thing up without being plugged in at 10 degrees.


Should start fine at 10 degreese regaurdless of what oil it had in it.
I never in 5 years had to plug my 7.3 in ever.


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## earnies2

Your rite it should start at 10 degrees or even 0 but she wont be happy.....


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## brad96z28

earnies2;651946 said:


> Your rite it should start at 10 degrees or even 0 but she wont be happy.....


Yep definitly might wake the neighbors, and take for ever to get heat but should not have trouble starting.


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## earnies2

brad96z28;651952 said:


> Yep definitly might wake the neighbors, and take for ever to get heat but should not have trouble starting.


Especally with two 5" stacks smoking up the street..............


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## MaineF250

Here's the key to getting a 7.3 to start when its cold.
-Fast cranking(good batts/starter)
- Hot glow plugs
Thats it, this one is my second 7.3 powerstroke and I was having starting issues with it last winter. I did plugs, a relay and batteries along with synthetic oil and still wouldn't start like my old '95 did. My starter finally quit last month and I put a ford reman in and even with the heavy-weight oil it fires over in 10 degree weather like nothing.


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## Doakster

MaineF250;653083 said:


> Here's the key to getting a 7.3 to start when its cold.
> -Fast cranking(good batts/starter)
> - Hot glow plugs
> Thats it, this one is my second 7.3 powerstroke and I was having starting issues with it last winter. I did plugs, a relay and batteries along with synthetic oil and still wouldn't start like my old '95 did. My starter finally quit last month and I put a ford reman in and even with the heavy-weight oil it fires over in 10 degree weather like nothing.


Couldn't agree more. Those two points are the key factors.

In actuality fast cranking is the number one factor in getting any diesel to fire, especially large commercial engines. Fast cranking = good compression = heat.

There is a company that makes a starting the will turn over the 7.3 much faster than the original but I forget who it is. I'd have to do a little researching.


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## MaineF250

Doakster;653500 said:


> Couldn't agree more. Those two points are the key factors.
> 
> In actuality fast cranking is the number one factor in getting any diesel to fire, especially large commercial engines. Fast cranking = good compression = heat.
> 
> There is a company that makes a starting the will turn over the 7.3 much faster than the original but I forget who it is. I'd have to do a little researching.


The navistar/caterpillar engines with the HEUI injection system is even more finiky because the computer needs to see at least 2500psi (i think) before the fuel solinoids even open. It doesn't take much, i didnt think my starter was dragging that much until I got my new one in. It made all the difference in the world.

I think the company your thinking of is DB electrical, I was gonna get one of their high-torque units off ebay for my truck but I needed it up and running quick so I got the ford one


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## Doakster

MaineF250;661641 said:


> The navistar/caterpillar engines with the HEUI injection system is even more finiky because the computer needs to see at least 2500psi (i think) before the fuel solinoids even open. It doesn't take much, i didnt think my starter was dragging that much until I got my new one in. It made all the difference in the world.


By fuel solenoids, I am assuming you are talking about the solenoids in the injectors. These are not actually on the fuel side they are on the High Pressure Oil Side.

The solenoids fire based on a signal from a timed signal from IDM, Injector Drive Module. When the solenoids open they allow high pressure oil to the intensifier piston inside the injector. The intensifier piston is stroked and in turn pressurizes/amplifies the low pressure fuel supplied from the fuel system already in the injector, to a high pressure that will now be injected through the nozzle of the injector.

The pressure that you were referring to the (2500), it's what called ICP, Injection Control Pressure. This is the same exact pressure that is coming from the High Pressure Oil Pump (it's just referred to as ICP) and supplied to the top of the injectors/intensifier piston/solenoid. It can run in a range of about 500-3500 depending on the strength/life of your pump.

The requirement to start a HEUI 7.3 is around 550 ICP, not 2500. 2500 is a relatively high value in the cycle and would be a relatively high throttle.


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## timberseal

How can you tell if your block heater is working properly? You would think Ford would have installed some indicator light or something  I played hell getting my truck to start this morning but I think the extension cord came pertially unplugged last night. It was around 10 degrees F overnight.


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## Doakster

timberseal;678639 said:


> How can you tell if your block heater is working properly? You would think Ford would have installed some indicator light or something  I played hell getting my truck to start this morning but I think the extension cord came pertially unplugged last night. It was around 10 degrees F overnight.


You should be able to trace the cord of you're block heater back. It will go all the way back to top of the oil filter, which is a oil/coolant cooler, the block heater is inserted here. The cable itself coming off the block heater will be orange in color. Just stick you're head directly under the oil filter and look up, the heater cord will be there.

Photo Here of Block heater: http://photos.thedieselstop.com/showphoto.php?photo=18736&papass=&sort=1&thecat=500

To see if it's working, plug the heater in, wait a 10-15mins or a little longer and touch the cord itself, it should be slightly warm, the longer you have it on the warmer the cord will be.

Although at 10 degrees it sounds like you have other issues if it's not starting, you can probable find your issue from the info in this thread.


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