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Discussion Starter · #1 ·
Hello all new here! I am pretty mechanical but when it comes to deisel diagnosting I am lost. I own a 96' F350 7.3 4x4 4 door. When I got the tuck it had a utility box on it and I was averaging 18 mpg. Over time i switched the bed out for a regular bed. Now over time I am down to about 12 mpg now. I came to the conclusion that the map sensor was bad do to power loss. I replaced it and my power is back. I also replaced ebs tube. ( Now shifting better) I noticed the other day when I changed my fuel filter that the fuel heater is disconnected and obviously broke. Will this have anything to do with fuel milage? Also I know my glow plugs are not working, but I keep the truck plugged in when temps are below 55 degrees. Also was wondering if anyone has ever used starter solenoid to replace the glowplug relay. Seems like same set up and 15 bucks cheaper. Any suggestions or help would be appriciated.

Thanks Dave :confused:
 

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It will work but it wont last, a starter solenoid is made to cycle for 15 sec or less and GP's cycle for up to 2 minutes, the starter one probably wouldnt last a week. If you want just about the best GPR there is, get a stancor relay, it is heavy duty and can handle the demand of the glow plug system and lasts way longer than a standard GPR

586-902 Stancor General Purpose / Industrial Relays
 

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as far as fuel bowl heater goes dont worry about it as far as glow plug relays go but either a replacement or one for a winch that is 100% duty cycle or a stancore
 

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The square thing is probably the Water-In-Fuel (WIF) switch which is a little solid-state device. On the starter relay for a GPR question: You need to make sure that whatever relay you try is NOT CASE-GROUNDED (it must be case-isolated like the factory ones), otherwise the glowplugs will not turn off. Go with the Stancor. If you need to go cheap, get a Sorensen MR99 from AutoZone or a GPR-109 from NAPA (and order them by the part number, not by application because they will try to sell you something else). Both will work, but don't count on them to last. Cheers!
 

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i just put in a cat relay and i'm loving the fast starts now....
 

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Discussion Starter · #8 ·
The square thing is probably the Water-In-Fuel (WIF) switch which is a little solid-state device. On the starter relay for a GPR question: You need to make sure that whatever relay you try is NOT CASE-GROUNDED (it must be case-isolated like the factory ones), otherwise the glowplugs will not turn off. Go with the Stancor. If you need to go cheap, get a Sorensen MR99 from AutoZone or a GPR-109 from NAPA (and order them by the part number, not by application because they will try to sell you something else). Both will work, but don't count on them to last. Cheers!
this looks like a fuse one of those goofy breaker ones square with two wires going to it. it is black, not on glowplug relay, clear top on it. Sits lose up near the eps. no one seems to know what it is. I will have to take picture of it.
 

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I'm new here, My 1995 7.3 The glow plug relay is located under the top eng. cover behined alt. it has 2 large wires on the top posts, and a small 2 wire harness at the bottom. ford does not have that one now, theirs now looks like the starter relay with the small wire harness comeing off 2 small terminals at the top, beside the 2 big one. What I need to know is how to replace the glow plugs?????? Jimmy
 

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Jimmy to replace glow plugs you will need a 13mm deep socket 13mm swivele socket 1/8in socket and I believe the glow plugs are 10mm You need to unplug the valve cover harness disconnect your intake pipes and remove pull the extra vacuum box off the air box pull the valve covers off and the valve cover gasket and harness from injectors and glow plugs and then you will be able to pull the glow plugs out good luck.
 

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Jimmy to replace glow plugs you will need a 13mm deep socket 13mm swivele socket 1/8in socket and I believe the glow plugs are 10mm You need to unplug the valve cover harness disconnect your intake pipes and remove pull the extra vacuum box off the air box pull the valve covers off and the valve cover gasket and harness from injectors and glow plugs and then you will be able to pull the glow plugs out good luck.
Thank's very much: Jimmy
 

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Jimmy,

You have the old style relay. Ford had a relay kit that came with a pigtail adapter to change the engine harness from the 2-wire weatherpack connector out to the small ring terminals. You don't have to get that kit to do it. You can simply cut off the weatherpack connector and crimp on ring terminals to the smaller wires. Cheers!
 

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i got my replacemnt relay off ebay. motorcraft, i think it cost me $35 . one thing i will let you know is this, you cant test the relay with a test light. the relay can still pass current to light the light, but not pass enough to trip the relay. its rare, but it does happen as was the case with me. when you turn the key foward, it should "click" loud enough to easily hear. if it doesnt, its bad. another thing is that if your fuel heater is broken, you are better off removing it entirely. if it is the thin wire style, if that slips off the posts and shorts out, you run the risk of major headaches. mine shorted, and tripped the anti theft in my pcm. would not allow the truck to start and can only be deactivated by a dealer. so after 2 tows, and $500 to reflash the pcm -total was $750 cause of that stupid heater. dont take the chance of leaving it in their just unglugged. it takes 5 minutes - remove it and youll never have to waorry about some mechanic plugging it in by accident.
 

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what is this cat relay?
i bought it a cat dealer, part 209-5581, it has 300amp contacts inside so hopefully it will last for a while. I've gone through three since i've owned the truck..
 

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Jimmy to replace glow plugs you will need a 13mm deep socket 13mm swivele socket 1/8in socket and I believe the glow plugs are 10mm You need to unplug the valve cover harness disconnect your intake pipes and remove pull the extra vacuum box off the air box pull the valve covers off and the valve cover gasket and harness from injectors and glow plugs and then you will be able to pull the glow plugs out good luck.
Thank's for the help folks, 7 out of the 8 were bad. Wasn't to bad of a job. My relay was good. 179,000 miles so I guess thats not to bad. Jimmy
 

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If you can swing it, I would replace the GPR anyway while you are in it, that way the whole GP system is new all at the same time and should last for many years with a good quality relay
 
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