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If you are talking about the glow plug relay on a 7.3,one of the big post will be 12 volts all the time,the other will get 12 volts when the key is turned on,most of the time one of the posts will be burnt and be black,it is a very common problem on power strokes.
 
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My experience has been bad glow plugs and not so much the relay.. When ya turn the key on does the voltmeter in the truck drop to 8 volts?

Why do you think it's a relay?

Find a shop with a Snap-on Red Brick and let 'em do a glow Plug test..

Also I've changed a ton of valve cover gaskets..

hope that helps some!

Laters!
 

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nos-stang said:
If you are talking about the glow plug relay on a 7.3,one of the big post will be 12 volts all the time,the other will get 12 volts when the key is turned on,most of the time one of the posts will be burnt and be black,it is a very common problem on power strokes.
I agree, but it needs to be cold when you check it.
 

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s_stang said:
My experience has been bad glow plugs and not so much the relay.. When ya turn the key on does the voltmeter in the truck drop to 8 volts?
actually especially on the earlier powerstrokes the GPRs seemed to go out a LOT. I am even on my third one on my 2000, but I doubt I will have to replace this one nearly as soon.
Don't go and get the one the book calls for, it's only rated at something like 80amps continuous, I did some searching through the books and found a continuous duty relay with a base that will bolt in place of the factory unit that is rated at 200 amps continuous (I believe the surge rating was 400 but would have to look it up again) had it on my truck awhile now and no more burned out GPR. Oh and it's half the cost of the one the 99 and up PSD calls for.
 

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Discussion Starter #6
I am thinking it is the GPR because it went from starting real easy to not starting all if I didn't plug it in or had to crank on it for a long time. Seemed llike it happened overnite
 

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I did some searching through the books and found a continuous duty relay with a base that will bolt in place of the factory unit that is rated at 200 amps continuous (I believe the surge rating was 400 but would have to look it up again) had it on my truck awhile now and no more burned out GPR.


Would you have the Part # on that rely you got ??

I seem to have to replace mine every other fall .. #4 so far on a 01


Dan
 

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Take a voltmeter and volt drop test across the two large terminals, have a buddy hit the key, should be less than .4 of a volt. If its not replace it.
 

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Most glow plugs that are burnt out have infinite resistance or a very high number. Take your voltage ohm meter and set to a low ohm resistance. Then check the resistance accross the terminals or the one terminal to ground. A low resistance ohm number is good. A high ohm number or open circuit is a bad plug.

BTW This is done without any power applied. Never use the ohm setting with power applied unless you want to buy another ohm meter.

Dave
 

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On that year truck unplug the connector at the top of the valve cover, two per side. Ohm the outside pins (5 per connector) to ground, less that 2 ohms is good. If there is any burnt pins on the conectors the covers need to be pulled and the inside harness inspected and any damaged parts replaced as this can eventually cause the truck to run on 4 cyls if the burnt areas get to the injector pins, running in this condition can also eventually knock out the 850 dollar IDM. Just a heads up if you find any.
 

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TRUKPULR said:
I did some searching through the books and found a continuous duty relay with a base that will bolt in place of the factory unit that is rated at 200 amps continuous (I believe the surge rating was 400 but would have to look it up again) had it on my truck awhile now and no more burned out GPR.


Would you have the Part # on that rely you got ??
napa part number ST36
 

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I've already replaced mine on my 95 Powerstroke. With all the reading I could find, everyone said the Ford GPR would only last about a year or so. I bought a continuous duty model from Mouser Electronics, part #586-902. It's about four times the size of the Ford unit, but still bolts in where the original was. There is a litle bit of wire modification to do, but it's simple. From what I've read this unit is nearly indestructable, and it's only about $42.
 

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The pre superduty trucks are hard on relays due to they will still bur the plugs even when the engine is hot, On my old 95 I rigged a relay in the circuit thjat would kill it when the starter cranked and also used a temp switch when the coollant was above 150*.

The Ford relays seem to outlast the napa units, my experience anyway.
 

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Jon the only reason the superduty units outlasted the presuperduty stuff has nothing to do with the run while hot deal it has to do with the presuperduty relays were 80amp rated teh superduty ones were rated at 95smp (still half what the continuous duty relay I use is rated for) my 2000 will turn on the GP relay 5 minutes after I shut it off after driving 250 miles ( I tried it just before replacing it last time) I went through the Ford unit in 2 yrs, a napa replacement in 2 yrs, and a ford replacement after that before switching to this continuous duty napa relay after I figured out that the factory units are barely sufficient to even run the GPs, let alone survive for any length of time. I saw all the guys telling everyone to buy the early unit (GP-109) becuase of it being so cheap and decided I needed to investigate what it actually was, why ford upgraded with the superduties and why they kept going out and that was my findings as listed above and why I did my research to find a relay that would live.
 

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Discussion Starter #16
I would wonder lf by installing a bigger than called for relay might not be hard on some other parts that are not so easy to replace. Thanks for all the replies. Who needs thedieselstop.com forum???
 

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richter69 said:
Just my observations, may just be me, what do I know................. :roll:
You know a lot, wasn't meant to put you down Jon, but I was also pointing out stuff that needs to be thought about too. We can all learn from each other on this site because no one knows everything. Just because Ford built it and put it in doesn't mean it was right, just means it was enough to get by. Thus if you look at the relays for the glow plugs you will find that the superduty glow plugs use 10 amps each, the early model used 8 amps from what specs could be found on them, so that is 80 and 64 respectivaly and the relays that ford spec'd for them were 95 and 80 thus leaving approx a grand total of 15 amps worth of give to account for all the connections, the wiring getting to the glow plugs themselves and the amount of extra amperage that would be used on initial heat up or due to extremes such as cold or heat when they are operating. Thus they will get he job done..... for awhile, and as long as NOTHING else causes any extra draw in the entire circuit. Having a relay that passes that current on higher then required means it's not part of the restriction and heat build up, and thus isn't getting hot and burning up wiring and connections and drawing the batteries down more then needed.

Digger on electronics restrictions cause heat which causes damage so having to big of a component like a relay reduces restrictions thus reducing heat thus reducing wear on the items in question. Now putting to big of a circuit breaker or a fuse on a circuit can cause problems.
 
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