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Thread: 2002 Ford 7.3L diesel won't start when its cold. Need help.

  1. #1
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    2002 Ford 7.3L diesel won't start when its cold. Need help.

    This is my first winter with this truck/diesel and once the temp. gets below 15 degrees it just won't start when its not plugged in. It turns over slowly and may cough but then die. This can be done until the batts, are dead. This only happens on the first start up of the day. I've read many of the postings here and they have been very helpful. Now here is some info. I have not switched to a lighter wieght oil. I only drive this truck maybe once every two weeks during the winter. New batteries have been installed. The glow plug relay has been verified to be operating when temps are 50 degrees and 5 degrees, although I still question it, so I plan to test everything again in the morning. I have ohm'd out the glow plugs at the connector on the valve covers and the wires back to the glow plug relay with good results, but this was done at 50 degrees in the garage and will be tested again in the morning.

    From my research I understand the negative wire going to the glow plug relay is controlled by the PCM and the hot lead is controlled by the ignition. This tells me the negative wire at the glow plug relay shoud not have any continuity to ground when the key is off. Is this correct? Because it does have continuity to ground all the time.

    When I turn the key and the glow plug light appears on the dash it turns off after about 10 seconds, the glow plug relay stays powered up though. Is this normal?
    This may or may not be off the subject or normal, but when I remove the ignition key and exit the truck the radio does not turn off right away. It does power down eventually though. Not sure if this is normal.
    I'm also concidering the batteries load to be drawing down by something.

    Any help would be greatful,

    Thank You

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    why wouldnt you just plug it in?
    i had a 7.3 diesel (1993) and it wouldnt start unless plugged in. i didnt check into anything else, altho i did run summer oil (its cold here in edmonton ab and -40 is not unheard of) its essential to plug any diesel in.

    does it start when plugged in? if you dont use it that often, maybe just take the batteries out a let it sit. that way your not having a slow pull off of them when its not in use. just an idea anyways

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    Quote Originally Posted by kowgirl View Post
    why wouldnt you just plug it in?
    i had a 7.3 diesel (1993) and it wouldnt start unless plugged in. i didnt check into anything else, altho i did run summer oil (its cold here in edmonton ab and -40 is not unheard of) its essential to plug any diesel in.

    does it start when plugged in? if you dont use it that often, maybe just take the batteries out a let it sit. that way your not having a slow pull off of them when its not in use. just an idea anyways
    I understand the importance of plugging in a diesel. Yes, it starts right up with no problems when plugged in. My biggest concern is taking it somewhere over night or leaving it for a week away from home where it can't be plugged in. We use two similar trucks at work, although they don't like cold starts, they do start when not plugged in.

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    Not a Power Stroke expert but it would seem, from your description, that the glowplug system is operating properly and that your problem is the slow cranking speed on the starter. All diesels need to be spun quickly on the starter. It may be that only being driven once every couple of weeks that the batteries are never getting fully charged. Maybe try putting them on a charger before the next start so that you have fully charged batteries.

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    I never figured a two battery system would be drained that much over two weeks. But when you factor in the cold, thick oil, and time it does make sense. I've got it charging and I see how it goes.

    Thank You

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    Senior Member mrjohnwayne's Avatar
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    in that cold of weather without being plugged in it will probably take a little longer to start... Yes it is normal for the glow plug circuit to stay energized after the light turns off. It will actually stay energized for 45-60 seconds...

    simple thing to try is to cycle the glow plugs a few times before trying to start to help warm up the combustion chamber. By cycling I mean turn the key on and let it sit for about 30 seconds and repeat a few times.
    John Wayne

    2000 F-350 7.3L Powerstroke 4x4

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    Quote Originally Posted by mrjohnwayne View Post
    in that cold of weather without being plugged in it will probably take a little longer to start... Yes it is normal for the glow plug circuit to stay energized after the light turns off. It will actually stay energized for 45-60 seconds...

    simple thing to try is to cycle the glow plugs a few times before trying to start to help warm up the combustion chamber. By cycling I mean turn the key on and let it sit for about 30 seconds and repeat a few times.

    I've tried cycling the glow plugs 2 to 3 times with no luck. I charged the batt. completely and it turned over fast like it should. It cranks over a few times fires up, revs up, then sometimes usually the first try or two it'll surge or rev up a second time and then die., after that it'll fire and rev up a bit and die until the batts. are dead.

    Thanks,
    Any other ideas?

  8. #8
    Senior Member mrjohnwayne's Avatar
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    might have some bad glow plugs. how many miles are on the truck?
    John Wayne

    2000 F-350 7.3L Powerstroke 4x4

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    The glow plugs ohm test ok. I've noticed my batt. voltage is low every time. I had the new batteries checked out. They were ok. Now that tells me that something is drawing the batts down. I tested and found that there was too much draw of .12, .003 is normal allowance. I elliminated the draw and went out this morning- the batts had 12.5 volts, It cranked over slowly and wouldn't start, not even fire. I am now going to ohm out the main batt. power and ground cables.

    I'll post what I find. Any help is appreciated. Thank You everyone.

  10. #10
    Senior Member mrjohnwayne's Avatar
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    hmm.. did you find anything on the battery cables. if the batteries have good voltage and still slow cranking I'd check the cables/connections.
    John Wayne

    2000 F-350 7.3L Powerstroke 4x4

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