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7.3l IDI Turbo GP Relay/Shutoff Solenoid Issues

Discussion in '6.9L IH & 7.3L IDI Diesels' started by 94IDIFactoryTurbo, Nov 26, 2019.

  1. 94IDIFactoryTurbo

    94IDIFactoryTurbo Registered User

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    Hello!

    I have been on this website for the last year since i purchased my truck. First time posting!
    It is a 94 7.3l IDI Turbo Diesel. it has 179k miles.
    Over the last few weeks I have been hunting down air intrusion(which i think i mostly have under control), and diagnosing a bad injector, and or glowplugs.


    So to get down to what happened to me today...

    I was cracking the injector lines while the truck was running to test and see if it changed the idling(looking for potential bad injector) and when I got to the line right next to the GP Relay it cut off the engine completely. I am assuming I touched the relay with my wrench and something bad happened.. I have been checking the fuses, etc looking for my answer with no luck...

    Also since this happened, the glow plug wait to start light will not shut off. I have it powered by a push button in the cab.

    My question is what could I have shorted out to cause the power to cut off the fuel shutoff solenoid and the glow plug relay?
     
  2. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    There's a possibility that there could be two separate issues that happened at the same time. I'm assuming that the engine won't restart (you did try, right?). Just to throw out a guess, I'd think that the engine died (and won't restart?) due to power not getting to the FSS (on top of the injector pump). I would also guess that you have a fusible link that's been burned. I had one, several years back, that burned inside the insulation, but didn't do anything to the insulation. It looked fine from the outside, but felt "loose" when I wiggled it. This really happened because of a radio in the truck burning itself up. I have no idea how it happened and may not have believed it if it hadn't happened to me. Once I stripped the insulation back and twisted the fusible link back together, I had power back to my FSS. We may need a little bit more info about the "wait to start" light. Does it stay lit all of the time? Is it only lit when the key is in the "on" position? Is the controller heating up the glow plugs or is just the light on? I'm not the most experienced with this style glow plug system so others may need to chime in to help. I do know that most people seem to run these controllers manually by using the push button to ground the controller.
     
  3. 94IDIFactoryTurbo

    94IDIFactoryTurbo Registered User

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    I appreciate your response!
    Well, to give an update...when I got off work today I managed to get the truck started, but only with a hot wire to the FSS.... as soon as I put a hot line on it the wait to start light stops illuminating and the push button works properly. but of course since its a hot wire as soon as I disconnect it the engine comes to a halt.

    Would you still say thats a possible fusible link? they appear to be in good shape, but i am not sure how to test them.
     
  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    You could do a continuity test from end to end. No continuity, bad fusible link. That may now be above my very limited electrical knowledge. It does sound like the issues are related somehow.
     
  5. 94IDIFactoryTurbo

    94IDIFactoryTurbo Registered User

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    I am thinking that most signs lead to the fusible links. I shall be doing a few tests tomorrow when I have more daylight.
    I've been reading a few posts on installing Maxi fuses in place of the old links, anybody have thoughts? If so, any sources I might be able to look into? Electricity and me arent the best of friends, but I can follow directions pretty well :cheers:
     
  6. franklin2

    franklin2 Full Access Member

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    I like fusible links. They are small, insulated from dirt and corrosion, and they work. Maxi fuses will work but they are larger and need a place to mount out of the weather and harms way. A fusible link is just a undersized piece of wire with special fire retardant insulation around it so it will not catch fire when it burns in two.

    There is one fusible link that you have burnt, but I do not know the exact location of it on your truck. The reason it's not over at the solenoid with the rest of the fusible links is because it's after the keyswitch, it onyl has power in start and run.
     
  7. 94IDIFactoryTurbo

    94IDIFactoryTurbo Registered User

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    Well said, it seems that they are the original ones. 25 years later and the only reason one fried was because of user error... I'll have to dig around for some diagrams to see if there are more on my truck hidden away somewhere like you mentioned. Will post again once I get back under the hood. These early sundown nights are killer...
    Love my truck, even if it is a bit needy :Thumbs Up
     
  8. franklin2

    franklin2 Full Access Member

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    The diagram below is not for your truck. It's for a 86 diesel, but you can see the theme of how they wired it up using a fusible link. I said the fusible link would not be over with the others, but they say this fusible link V in 1986 is over near there, I will see if I can find a picture. Remember, this is an 86, not a 94. Too bad we do not have a set of these diagrams online for a later truck.

    [​IMG]
     
  9. franklin2

    franklin2 Full Access Member

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    In this picture on a 1986 truck, if you look carefully you can see the fusible link V in all that mess. Your truck will not have that glowplug relay and some of that other stuff.

    [​IMG]
     
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  10. 94IDIFactoryTurbo

    94IDIFactoryTurbo Registered User

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    Sorry for the delay in responding, with the holiday season and all that I havent had much spare time lately. I spent a few hours replacing a burnt out fusible link that didnt seem to fix the issue at first. Replaced a few fuses that looked like they werent good, and called it a day.. came back to it today and the issue is not presenting itself anymore. I appreciate all the responses. Will keep you all posted if the issues re occurs. in the mean time i will keep a few wires laying around for if the issue pops up again down the road to hopefully avoid being stuck on the side of the road.

    In the mean time i shall go back to the other projects the old IDI needs...

    Thanks everyone!
     

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