Rough Cold Start
Tuned
Joined: Sep 2004
Posts: 420
Likes: 106
From: Jackson, WY
FWIW -- my first winter here in Wyoming, and my truck spent its entire life in California. Even at single digit degrees Fahrenheit, without plugging in the truck, I can cycle my glow plugs one full cycle, then again for 15/20 seconds, and it will fire right up. I've only ever had to crank it twice one time and it was suuuuuper cold and had been sitting for a week.
I'm also running Motorcraft 15W40. With the low mileage on your truck, I'd just make sure your glow plugs and relay are operational. 24 degrees isn't cold enough to have to plug in IMO.
I'm also running Motorcraft 15W40. With the low mileage on your truck, I'd just make sure your glow plugs and relay are operational. 24 degrees isn't cold enough to have to plug in IMO.
Laughing Gas
Joined: Oct 2008
Posts: 1,106
Likes: 154
From: Kansas City KS
If you put your meter on the 2 large terminals with the key on you should see 12v.
In your first post you said you saw a voltage drop while the gps are on. And this may be correct but the solenoid could have worn contacts on the inside. Resulting in low voltage on the gp side. Here's how to test that voltage.
Key OFF:
-- Wire from the battery should read aprx. battery voltage, ~ 12.5V
-- Wire to the glow plugs should read zero
Key ON:
-- Wire from the battery will read SOME less, probably aprx. 11V
-- Wire to the glow plugs will read a little lower, but should be no more than 0.3V below the wire from the battery.
So if the DIFFERENCE between the two, WITH THE KEY ON, is more than 0.3V, replace the relay. It's still contacting, but supplying insufficient voltage to the plugs. DON'T bother comparing the battery side with the key OFF to the plug side with the key ON; that really doesn't tell you anything about the relay. If the difference between key OFF and key ON is a lot (like, it goes down to the 9-ish volt range), that would indicate weak batteries (poor-man's load test, basically).
Or the next cold morning jump the solenoid with a screwdriver. If it starts better you need a new solenoid. Buy a good one trombeta or motorcraft.
In your first post you said you saw a voltage drop while the gps are on. And this may be correct but the solenoid could have worn contacts on the inside. Resulting in low voltage on the gp side. Here's how to test that voltage.
Key OFF:
-- Wire from the battery should read aprx. battery voltage, ~ 12.5V
-- Wire to the glow plugs should read zero
Key ON:
-- Wire from the battery will read SOME less, probably aprx. 11V
-- Wire to the glow plugs will read a little lower, but should be no more than 0.3V below the wire from the battery.
So if the DIFFERENCE between the two, WITH THE KEY ON, is more than 0.3V, replace the relay. It's still contacting, but supplying insufficient voltage to the plugs. DON'T bother comparing the battery side with the key OFF to the plug side with the key ON; that really doesn't tell you anything about the relay. If the difference between key OFF and key ON is a lot (like, it goes down to the 9-ish volt range), that would indicate weak batteries (poor-man's load test, basically).
Or the next cold morning jump the solenoid with a screwdriver. If it starts better you need a new solenoid. Buy a good one trombeta or motorcraft.
Thread Starter
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Mountain Pass
Joined: Apr 2021
Posts: 130
Likes: 19
From: Idaho
If you put your meter on the 2 large terminals with the key on you should see 12v.
In your first post you said you saw a voltage drop while the gps are on. And this may be correct but the solenoid could have worn contacts on the inside. Resulting in low voltage on the gp side. Here's how to test that voltage.
Key OFF:
-- Wire from the battery should read aprx. battery voltage, ~ 12.5V
-- Wire to the glow plugs should read zero
Key ON:
-- Wire from the battery will read SOME less, probably aprx. 11V
-- Wire to the glow plugs will read a little lower, but should be no more than 0.3V below the wire from the battery.
So if the DIFFERENCE between the two, WITH THE KEY ON, is more than 0.3V, replace the relay. It's still contacting, but supplying insufficient voltage to the plugs. DON'T bother comparing the battery side with the key OFF to the plug side with the key ON; that really doesn't tell you anything about the relay. If the difference between key OFF and key ON is a lot (like, it goes down to the 9-ish volt range), that would indicate weak batteries (poor-man's load test, basically).
Or the next cold morning jump the solenoid with a screwdriver. If it starts better you need a new solenoid. Buy a good one trombeta or motorcraft.
In your first post you said you saw a voltage drop while the gps are on. And this may be correct but the solenoid could have worn contacts on the inside. Resulting in low voltage on the gp side. Here's how to test that voltage.
Key OFF:
-- Wire from the battery should read aprx. battery voltage, ~ 12.5V
-- Wire to the glow plugs should read zero
Key ON:
-- Wire from the battery will read SOME less, probably aprx. 11V
-- Wire to the glow plugs will read a little lower, but should be no more than 0.3V below the wire from the battery.
So if the DIFFERENCE between the two, WITH THE KEY ON, is more than 0.3V, replace the relay. It's still contacting, but supplying insufficient voltage to the plugs. DON'T bother comparing the battery side with the key OFF to the plug side with the key ON; that really doesn't tell you anything about the relay. If the difference between key OFF and key ON is a lot (like, it goes down to the 9-ish volt range), that would indicate weak batteries (poor-man's load test, basically).
Or the next cold morning jump the solenoid with a screwdriver. If it starts better you need a new solenoid. Buy a good one trombeta or motorcraft.
So yesterday I went out and measured the resistance on the glow plugs. I was using my cheap Harbor Freight meter and due to the short cables I couldn't seem to find a real good ground, but I was able to consistently measure them all at 2.8 ohms.
I was measuring 12.1V on the GPR (I think, I didn't write it down) with the key off and 0V on the switched side. With the key on I was measuring 11.1V on the battery side and 10.3V on the switched side.
I had also plugged it in for just over 3 hours and it fired right up like it would during the summer.
This morning I got the same voltage measurements so for kicks I held a screwdriver across the GPR for about a minute. It seemed to make no change in the way it started so I guess I have to settle for this being a 15W40 issue. I guess on my next oil change I'll find out. That likely won't be until next winter.
Got Data?
Joined: Dec 2012
Posts: 4,260
Likes: 1,390
From: Lake Stevens, WA
Some good diagnostics here - now you know your GPs are doing their job. 2.8ohms is a bit high. As mentioned, normal readings are 0.6 - 2.0 ohms when measured at the valve cover gasket pins. Did your meter show "0" ohms with the test leads shorted together? Want to make sure the meter resistance is not contributing to that 2.8 ohm reading. Like you noticed, a good ground is important for a reliable reading as well.
Replacing your GPs with new motorcraft units is not a bad job if you want to tackle it - could improve your cold starts a bit. I'd suggest changing out the GPR as well if it's original since, to @T-wood 's point, it's dropping considerably more than 0.3V across the contacts when engaged.
But sounds like you have a work around for cold starts where you can plug in, or accelerate through the romps.
Replacing your GPs with new motorcraft units is not a bad job if you want to tackle it - could improve your cold starts a bit. I'd suggest changing out the GPR as well if it's original since, to @T-wood 's point, it's dropping considerably more than 0.3V across the contacts when engaged.
But sounds like you have a work around for cold starts where you can plug in, or accelerate through the romps.
5th Wheeling
Joined: May 2016
Posts: 41
Likes: 5
From: Olathe, Kansas
I just changed the GPR on my 2002 7.3 and it made an instant difference and only took about 15 minutes. The rough idling and then it smooths out sounds like your glow plugs are shutting off and then once the engine starts generating enough compression than the idle smooths out. I'm actually exited for the temps to drop in the single digits to see if it will start without plugging it in.
More Turbo
Joined: Sep 2018
Posts: 544
Likes: 213
From: UT
x2 for this......I have run one on all 5 of my trucks and have never had an issue with it. I wish there was a way around the GPCM on the Excursions.
The Monster
The Monster
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,353
Likes: 5,946
From: Lake Hartwell, GA
If you end up needing a new GPR, check out the recent thread about your options I have linked below. Then you may make a decision based on your gut feeling and the advice and experiences from others.
Link: https://www.ford-trucks.com/forums/1...-best-gpr.html
Link: https://www.ford-trucks.com/forums/1...-best-gpr.html
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Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
Check voltage directly on the battery post. If it's more than 12.2 then you have connection issues between them and the GPR. I would also check them individually, with a cable disconnected from one of the batteries.
I feel .2 ohms resistance between positive terminal and load connection (in this case, positive lug on GPR) is acceptable. Anything more and I keep searching.
0.7v drop across the GPR is also bad. Should be the same on both sides when energized.
My rule of thumb for plugging in was anything below freezing plan on 2-4 hours. I used a Christmas light timer (outdoor and 1500w rated).
Below 20 I just plugged it in all night. Now that I have new glow plugs and injectors It will start fine down to 20, but I still try to get it plugged in any colder than that.
Since I left AK I don't see as many nights that cold, though we did have -8 on new years eve.
Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
I just changed the GPR on my 2002 7.3 and it made an instant difference and only took about 15 minutes. The rough idling and then it smooths out sounds like your glow plugs are shutting off and then once the engine starts generating enough compression than the idle smooths out. I'm actually exited for the temps to drop in the single digits to see if it will start without plugging it in.
Thread Starter
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Mountain Pass
Joined: Apr 2021
Posts: 130
Likes: 19
From: Idaho
Well it was -3*F this morning and it didn't take my wife long to kill the batteries trying to start it... I put my GooLoo GP4000 (rated for 8L diesels or something like that) and it went from a full charge to dead in about 8 seconds of cranking. Put my 15amp charger on it for a few hours and the battery voltage was read 13.3V with the charger off. Hooked it back up and I still couldn't get it to start. I'm starting to suspect I have a bad battery or 2 now... a couple winters ago these batteries (brand new at the time) fired it up no problem in these same conditions without being plugged in or jumped. Granted I suspect it had 5W oil in it at the time and it has 15W right now.
So I guess I will be looking for new batteries. These ones are 850CCA Duracells I got from Sam's Club.
So I guess I will be looking for new batteries. These ones are 850CCA Duracells I got from Sam's Club.
FTE Leadership Emeritus
Joined: May 2014
Posts: 27,353
Likes: 5,946
From: Lake Hartwell, GA
I lost my faith in lead acid batteries several years ago. Warranty and prorating is good, but not having to replace them well before I should be is better. Even my riding mower John Deere has a lithium battery in it I am so against lead acid now.
FTE'r Y2KW57 made the process of choosing an AGM battery easy for us in the thread linked below.
Link: AGM Group 65 Battery Comparison
If you decide to go that route that is. I bought some NorthStar AGM batteries a few years ago and they are still going like they were new. If they last me 6 years I am even money without having to replace them, so maybe a bit in the positive. If they last me more than 6 years than I am in the positive financially and manual labor wise. Also, I am not left stranded on BLM land out in the middle of nowhere either. That is a good thing in my opinion.
FTE'r Y2KW57 made the process of choosing an AGM battery easy for us in the thread linked below.
Link: AGM Group 65 Battery Comparison
If you decide to go that route that is. I bought some NorthStar AGM batteries a few years ago and they are still going like they were new. If they last me 6 years I am even money without having to replace them, so maybe a bit in the positive. If they last me more than 6 years than I am in the positive financially and manual labor wise. Also, I am not left stranded on BLM land out in the middle of nowhere either. That is a good thing in my opinion.
Cargo Master
Joined: Aug 2003
Posts: 2,332
Likes: 442
From: Eastern Washington
While I do like AGM's, and have been using them in various applications for over 20 years now, a flooded lead acid battery is still the best bang for the buck if conditions do not favor the AGM.
I usually get 6-8 years out of them depending upon use. If your charging system is in good shape and you don't let them sit for too long and/or freeze, they will serve you well.
Before or after you replace your batteries check voltage/resistance between all points. These trucks are known for the crossover cable and terminal ends becoming corroded internally and causing charging issues.
I usually get 6-8 years out of them depending upon use. If your charging system is in good shape and you don't let them sit for too long and/or freeze, they will serve you well.
Before or after you replace your batteries check voltage/resistance between all points. These trucks are known for the crossover cable and terminal ends becoming corroded internally and causing charging issues.
Thread Starter
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Mountain Pass
Joined: Apr 2021
Posts: 130
Likes: 19
From: Idaho
It was a pleasant 19* outside this morning and I got the new Trombetta installed. The only quirk I ran into was that the Trombetta did not come with new nuts for the studs so I assumed they planned on re-using the old ones. The old ones were course thread and the Trombetta is fine thread though so I had to make a run to a store.
Key Off:
Batteries: 12.25V
GPR in: 12.25V
Key On: (Vacuum Pump was also running)
Batteries: 11.40V
GPR in: 11.15V
GPR out: 11.10V
It probably took me about 30 seconds to measure those voltages with the key on and I jumped in and fired it up. It started almost immediately with very little romping. It revved up and down about 2 times and mellowed right out.
Prior to this I was fully cycling the glow plugs 2 to 3 times (like a 10 minute process) and it was still pretty rough to start it. Tomorrow morning I will go out and try to start it after the wait to start light goes out and see how it does.
Thanks for all your help guys!
Key Off:
Batteries: 12.25V
GPR in: 12.25V
Key On: (Vacuum Pump was also running)
Batteries: 11.40V
GPR in: 11.15V
GPR out: 11.10V
It probably took me about 30 seconds to measure those voltages with the key on and I jumped in and fired it up. It started almost immediately with very little romping. It revved up and down about 2 times and mellowed right out.
Prior to this I was fully cycling the glow plugs 2 to 3 times (like a 10 minute process) and it was still pretty rough to start it. Tomorrow morning I will go out and try to start it after the wait to start light goes out and see how it does.
Thanks for all your help guys!
Laughing Gas
Joined: Oct 2020
Posts: 785
Likes: 150
Sounds like you have it whipped! I had my GPR die over Christmas while visiting family. For a short term work around I just wired the AIH relay to the glow plugs since I have deleted the AIH. I have a new Trombetta waiting for motivation to swap it out.