Filter light flashing and black smoke???

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Mammoth73, Sep 15, 2018.

  1. Mammoth73

    Mammoth73 Registered User

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    '93 7.3idi turbo 260k

    I've been getting major power loss and black smoke lately. But the fuel filter light started flashing intermittently at idle...

    Replaced the filter and the light went away for a couple days with no real improvement in performance. But I'm getting excessive black smoke when under hard acceleration or when I'm towing.

    I've read all I could find on it but have just about ruled out everything I can think of. It seems as if I'm having 2 contradictory problems that both started around the same time.

    Within the past year I've cleaned the tanks and put new pickups in, new lines up to the pump, new pump, new filter, new injectors and had it timed and she ran like a champ for about 2 weeks after the timing then just started going downhill.

    The filter light is intermittent in the sense it'll start blinking between shifts or at idle, go away for a good bit, then come back after the first shift if I leave it parked and running for a few.

    What befuddles me is that I'm getting black out the tailpipe along with some kind of fuel restriction, but she was running like a Kenyan on speed just a couple weeks ago...

    Has anyone seen anything like this before or maybe at least point me in the right direction before I start throwing any more parts at it?

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  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Do you have any gauges? I don’t remember. Try unplugging that filter sensor and see if it still randomly comes on, usually they don’t blink like that so that may just be a wiring issue.

    For the black smoke, if you get air fed into the pump housing from the fuel line it will open the metering valve to purge it, which is effectively like going full throttle for a moment, which could give you the black smoke, but it could be you’re pump is getting worn out. Have you checked your air filter?
     
  3. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Just to clear things up, you replaced "the pump", by this do you mean the injector pump(IP) or the lift pump?

    But the problem actually sounds like you have a supply line clog/restriction. This could be an inline filter that someone added anywhere between the tank and the stock filter, even before the fuel selection valve.
    Could also be a pinched/kinked hard or soft line, and maybe when you replaced the pickups you used something that could collapse under suction or suck itself to the bottom of the tank?

    When you said it ran great for two weeks does that mean there wasnt any black smoke during those weeks?
     
  4. Mammoth73

    Mammoth73 Registered User

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    No gauges yet but I foresee a pyro sneaking it's way into the budget soon.

    By pump I did mean lift pump and yes there was virtually no smoke. The PO had the inj pump done just before I got it. Checked the filter, it's dirty but it's been way worse with nowhere near the smoke I have now no matter what I did to the throttle but I'll be getting a new one nonetheless.
    I've got a 5" clear vinyl connecting line from AN to the pump. Its got bubbles but they've always been there and never gave me this kinda smoke. When I had my air intrusion problem I didn't have this either.

    Is there any way to go directly to the pump with anything other than a hose clamp?

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  5. Mammoth73

    Mammoth73 Registered User

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    I've got stainless braided AN from the tank I'm using up most of the way to the pump with all new fittings as well as cleaned/lubed all the connections when I did and just checked the soft ones and didn't see any kinks or potential obstructions.

    Guess I'll use the rest of that stainless braid going straight to the pump and see if that gets rid of my air bubbles or problems.

    I'll also order the new air filter and she's due for an oil change as well. I should also add that it's a new selector valve. OEM part # not what you find in the stores out here.
     
    Last edited: Sep 16, 2018
  6. Clb

    Clb Another old truck Supporting Member

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    Who built the i.p.\inj.?
    Time to check timing.
     
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  7. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I timed the truck not long ago.

    You need to find the source of the air bubbles, If your truck fires up every time like you’re not loosing prime then it’s on the suction side of the system, so check everything pre lift pump. I think I remember making a comment about it smoking at idle saying that those injectors may need going through, or you may have a pump issue.
     
  8. Mammoth73

    Mammoth73 Registered User

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    You definitely did. That kinda sucks cuz I just put the damn things in a couple months back. Didn't have them tested before hand but I got them off rock auto as "new" Delphis but IIRC they were stanadyne coded and was sure not to damage the tips. it's weird since the problem seems intermittent at times. After the injectors were put in it ran like a champ, then after the clutch/ flywheel conversion it went back to sluggish. Then after the timing it ran great again, now back to crap.
    Would injectors fail intermittent like that?

    I might also add that my fuel filter actually loosened itself and was spewing diesel just before these issues began. I suspect the vacuum pump going out caused extra vibration which could've done that. But after I tightened it back up it was like new again for the trip home but that's it. Made sure to lube and prime the new filter and it's on tight.

    I'll try the filter wire and see if that changes anything.
    Although now that you mention it did seem to crank a little longer than normal yesterday morning. Then I guess I'll run that stainless braid line the rest of the way to the pump and see where that puts me.


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  9. DaveBen

    DaveBen Supporting Member Supporting Member

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    Run some injector cleaner thru your fuel system. That might clear it up.
     

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