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7.3 IDI slow to start after fuel line replacement

Discussion in '6.9L IH & 7.3L IDI Diesels' started by J Mark, Sep 16, 2020.

  1. J Mark

    J Mark Registered User

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    Hi folks, new to the forum and new to diesel truck ownership also. I have a 1990 F250 7.3 IDI, had it for about a year. Had a local mechanic replace the fuel lines recently due to cracking, and since then it's had a hard time starting when cold. It'll cough a bit of smoke right away, like it wants to catch, but then takes 20-30 seconds of cranking until it actually starts - at which point it runs a bit rough for a little bit longer. Before the fuel lines were replaced it started up just fine. Oh also there is a clicking sound after the 'wait to start' light goes off before I turn the key to start. Is it possible the mechanic didn't reconnect something needed for the initial feeding of fuel at startup? Or something else?
     
  2. frankenwrench

    frankenwrench overkill is under rated!

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    May have jarred a glow plug wire loose. What it sounds like to me with the clicking. If u get immediate belch if smoke when cranking it's getting fuel. But no glow plugs, hard to start. Even if it's just a few disconnected.
     
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  3. gandalf

    gandalf Senior Member

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    Welcome to the best Ford IDI forum there is! You'll find us a friendly bunch, and more knowledgeable than the mechanics at many Ford dealers. They simply don't want to deal with these old diesels.

    You've got to tell us more about your truck. How many miles? Has the injection pump been replaced? How about the glow plugs? The lift pump? Are you running a lift pump or have you converted to an electric fuel pump? Add some basics about your truck in the signature block, so it appears on your every post.

    Based on what you've said, I think you have an air leek in your fuel line. You've got to crank until you eliminate the air in the fuel lines. Be careful--if you crank more than 15-20 seconds quit and let the starter cool for a couple minutes. That starter is fighting high compression turning over the diesel, it's working hard.

    The clicking sound is probably your glow plug controller, in which case you shouldn't worry. It might also be an electric fuel pump, in which case it's normal.

    More will follow me with additional suggestions.
     
  4. J Mark

    J Mark Registered User

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    Thanks for the suggestions - on my issue and on using the forum! My truck is all stock as far as I know, 91,000 miles. I've had it for about a year but haven't driven it all that much. It was an old guy's occasional hauling truck for most of its life, I don't know if the IP or glow plugs ever got replaced. Also don't know about the fuel pump upgrade or not.

    Glow plug wires all seem connected as far as I can tell, and a once-over on fuel lines seems like everything's connected too. Is there a way to locate air leaks in the fuel lines that might not be obvious on first glance?
     
  5. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Look for wet places along your fuel lines. Air leaks will usually, but not always, let fuel out after the engine is shut off. Air leaks can be a PITA to find. You didn't say which fuel line(s) cracked, but I'm going to assume that it's one of your injector lines since they seem to be the most common. I'm also going to suggest to start looking at the return caps on your injectors closely. If the mechanic was working around them, he/she could have bumped one or more of the caps or rubber lines between them. That's all it takes to start a leak if the O-rings underneath them are old and hard. Another thing to check is that all of the metal clamps that hold the injector lines are in place. If one is missing, it can let another injector line crack.
     
  6. J Mark

    J Mark Registered User

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    Thanks, y'all. Upon further inspection it's leaking fuel (and probably sucking air too) from the top of the fuel filter, around the fuel heater.
     
  7. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    I'm glad that you found the issue. That's a common place for a leak to happen. Since the heater does next to nothing, even when new, a lot of people just delete it. You can pull it out and tap it out to 1/2" NPT and put a plug in there.
     
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  8. Cubey

    Cubey Full timer RVer

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    Yellow natural gas/propane rated teflon tape might work as a band aid for the threads. I used it for my electric fuel pump conversion fittings since I already had a very old roll of it from RV propane lines. The stuff doesn't seem to go bad with age since it's not leaking any from any of the fittings after 6 months of being exposed to diesel. I've also used it on propane lines in my current RV without any leaks. It should hold up better to diesel than white water rated teflon tape. It's thicker/more rigid, not super stretchy.
     
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  9. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    The heater on the 7.3 style filter head doesn't thread in.
     

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