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Ford F250 with the 7.3 Diesel


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  #1  
Old 11-26-2009, 11:19:29 PM
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Brickman Brickman is offline
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Default Ford F250 with the 7.3 Diesel

i have a 1999 ford f250 with the 7.3 diesel , all of a sudden it wont start below 50 degres outside , how do i tell if the glowplugs are workin ,if i take them out how do i tell if they are good. dont want to buy all new ones if i dont have to. thanks for any and all advice. ron brown in central illinois
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Old 11-27-2009, 01:00:35 AM
KEB KEB is offline
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Default Re: Ford f250 with the 7.3 Diesel

Check the glow plug relay. It's on the top of the engine, near the passenger side of the fuel filter. There are two relays in that area, as I recall the one closest to the fuel filter is the glow plug relay (but don't quote me on that). It looks a lot like a plastic starter selenoid.

When you first turn on the key, there should be 12 or a little less volts at both heavy terminals. One is connected directly to the battery, the other goes to the glow plugs. The small terminals are the control wires. Another quick check is to put a voltmeter across the two heavy terminals. With the key off, there should be battery voltage across the terminals. With the key turned on & the engine cold, there should only be a few 10ths of a volt across the relay terminals. If you still get 12 volts across the terminals when the glow plugs are supposed to be on, it means either the glow plug relay is bad or there's a problem in the relay wiring.

These things have a habit of burning the glow plug wiring where it enters the valve cover, but I wouldn't think that would cause all of them to go out at once.

I currently have one bad glow plug in mine, and it'll start reliably at 20 or 30 degrees. Need to get it fixed before it really gets cold.

If you need to replace the relay, call around for a price. Ford wants a fortune for an OEM one, but most auto parts places can get an equivalent replacement for a lot less.

Keith
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Old 11-27-2009, 10:43:06 AM
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Default Re: Ford f250 with the 7.3 Diesel

You may want to check your batteries,load test them indvidually if you have a weak battery it will show up when the temp gets cooler thus resulting in too slow of a cranking speed for the HEUI fuel injection to work, seen it many, many times. If you do decide to pull the glow plugs out you can check them with a volt ohm meter the exact spec escapes me but I believe it is 2.0 ohms. Usually you will find an open one or two. I always replace all of them, since the valve covers have to come off and it is a messy job. Plus they are most likely all the same age and subject to fail like the already failed one. Also as Keith mentioned about the relay, It is not a starter relay although it looks identical externally it is different internally. I have seen a bunch of folks put starter relays in place and they will not hold up long, the glow plug relays have a continous duty primary coil in them so they will withstand being engaged more frequently and for longer periods of time.

Denny

Last edited by oldironcollector; 11-27-2009 at 10:52:57 AM.
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Old 11-27-2009, 10:54:10 AM
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Default Re: Ford f250 with the 7.3 Diesel

I had one at one time. I tested by taking a test light one side to hot wire other side to glo. plug. If it lights it is good if not plug is burned out . If 6 or more light then it is most like y the relay bob
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Old 11-27-2009, 11:05:59 PM
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Default Re: Ford f250 with the 7.3 Diesel

thanks guys i will look at it in a few days and let you know what i find out. ron brown in central ilinois
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Old 11-28-2009, 12:35:29 AM
Mike Miller Mike Miller is offline
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Default Re: Ford F250 with the 7.3 Diesel

On Earlier Trucks (you will have to check a schematic to see if the 99 is the same) the glow plug timer had two circuits one for each bank. Use a test light or voltmeter to verify voltage to the plugs on both banks. If one bank is out it will be hard starting. The glow plugs, have a nasty habit of one burning out. By removing the wire from GP Timer, then check for continuity to ground, if open circuit it is bad. If you replace one GP, within a very short time several more on the same bank will burn out.It has something to do with the older glow plugs having a higher resistanance than the new one. I suggest if you find a bad one, replace all four on the same bank at the same time. Also these glow plugs have a nasty habit of bulging when they burn out, end result is they twist off and you end up drilling them out. Suggest doing a search to see if there are any tips on "easy removal".
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Old 11-28-2009, 08:59:38 PM
Dirk Jr Dirk Jr is offline
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Default Re: Ford F250 with the 7.3 Diesel

Most likely it's the relay. Check that first.

If you decide to change the glow plugs, use Motorcraft (Beru) plugs only. The off brands are prone to swelling. Also the UVC harnesses should be changed as well. It would suck to change the plugs only to have the harness take a dump. That means your pulling the valve covers again.
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Old 11-28-2009, 09:35:09 PM
Mike Miller Mike Miller is offline
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Default Re: Ford F250 with the 7.3 Diesel

I worked for an airline and their fuel service trucks were always having problems with hard start. We were stuck with corperate telling us where to purchase parts so didn't get the experience with the motorcraft glow plugs not being as prone to swelling.Brings back the old saying "you get what you pay for".
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Old 02-27-2010, 01:21:54 AM
rsieck rsieck is offline
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Default Re: Ford F250 with the 7.3 Diesel

Here is an excellent write up about the glow plug relays. From what I've read is that the stock GPR gets 12-14v to it, and it was only designed for 12v. So over time it fails. This write up is for a heavier relay. You can get it for about $40, which the last time I priced a GPR from Ford or a parts store, they wanted around $80. I bought one of these $80 GPR's and it burned out within a week. I put the updated relay and haven't looked back!!

http://www.guzzle7pt3.com/s_gpr.php
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Old 03-01-2010, 09:32:18 PM
Dirk Jr Dirk Jr is offline
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Default Re: Ford F250 with the 7.3 Diesel

With a 143k on my Super Duty I think its time for the Stancor relay.
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Old 03-13-2010, 02:05:36 PM
Randy L Peterson Randy L Peterson is offline
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Default Re: Ford F250 with the 7.3 Diesel

more then likely the Glow plug relay.. has a yellow wire going to it if I remember.. Amps are what kills the relays not Voltage.. To test the glow plugs you have to know which wires in the Connector go to the glow plugs.. Usually the bigger terminals Otherwise you have to pull the valve covers. Have also had to replace a lot of the Valve cover gaskets and the under valve cover wiring harness' .. Compression is also Key in these engines.. Lack of Airfilter changes will Dust the turbo and Kill the cylinder usually the Rear one on the Passenger side or the one before it.. Good engines take a beating just a little bit of nic nak stuff you have to stay on top of when they get some miles on em.. Good LUCK
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