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1992 Ford F-350 7.3 IDI NA drives 1/2 mile then dies and has hard starts...

Discussion in '6.9L IH & 7.3L IDI Diesels' started by foundonroaddead, Jan 20, 2021.

  1. notenuftime

    notenuftime Full Access Member

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    Screenshot_20210121-092109.png
     
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  2. foundonroaddead

    foundonroaddead Registered User

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    I have ordered new shower heads for each tank. May need to buy the whole unit too but will update once i manage to drain the tanks out and drop them. Considering replacing the fuel switcher valve (finally realized that was what FSV was after some reading :p) while i’m at it. I can hear it go *thunk* as i move the dash switch so it does something. Due to sitting so long, with 1/2 full of diesel in each tank, and all the sudden pumping it all empty, i’m guessing it pulled out a lot of build up out in the process as the barrel i put it in is completely black even though i put 2 filters before my little $10 ebay pump.
     
  3. John Scott

    John Scott Registered User

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    Ok so it sounds like its isolated to the front tank... there's 2 orings in the connector to the switching valve might check and make sure they r ok.... from there I would inspect or replace the rubber line from the tank to switching valve... also might pull sender out and make sure there's no rusty holes in the pick up tube inside the tanks
     
  4. notenuftime

    notenuftime Full Access Member

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    In all honesty I say just get rid of the front tank and run the rear. FSV valves suck, unless you build a manual one. Add a inline fuel filter as well.
     
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  5. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    He has said that it will do this on both tanks, but it will do it worse on the front tank. He also said that both tanks are over 3/4 full so the shower heads are probably not the issue. When they fall off, you'll run out of fuel at about 1/4 tank. Since you can gear the FSV working and both thanks are almost full, I tend to lean toward the FSV also not being the issue unless there's a way that it can pull outside air into the system which should show up as at least dampness on or around the FSV (I think). Do you know why the truck was parked for so long? Was it having these issues back before it was parked? I believe that some have said on here that the bowl on the bottom of their Facett wasn't tight enough. If it's not completely tight, and there is some type of build up on the shower heads in the tanks, then the pump could be straining enough to pull air in through a not-quite-completely-sealed seal. Maybe the front tank pick up is more plugged than the rear one and that's why the problem's worse on the front tank?
     
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  6. foundonroaddead

    foundonroaddead Registered User

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    The truck was parked because when my dad had it as his daily driver, every time he’d leave a jobsite he would have to sit there and crank it for 3-5 minutes with the mechanical pump just to get it to start up again. I think he said it ran fine after it was running but it seems to me like air intrusion would cause the suction of the fuel to be lost and drain all the way out back into the tanks.

    I was leaning towards that idea of the heads being clogged as well. Before the truck was ever running we drained out all the old fuel and it was real dirty, even with two inline filters. they picked up all kinds of gunk on their own though. so with that in mind, and it sitting so long, pumping all 15 gallons or so out in a 3 hour span must have filled the little heads with particulates.

    my analogy of it was it’s like taking a deep breath and holding your nose but still trying to breathe. you can stay awake doing it on your couch but hold your nose while going for a run and you’ll pass out cause your lungs cannot keep up quick enough. if that makes sense.

    truck has 170,,,k and he managed to put only 50k on it from the span of 1996 to 2008.
     
  7. foundonroaddead

    foundonroaddead Registered User

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    However even if it’s an issue isolated to the fuel tank, i can’t process how i was able to drive it real hard for probably 10 minutes about 2-3 miles one day and then it craps out and starts dying every 15 seconds to the next day only being able to go half a mile and it start the same problem once again. can’t seem to find a consistent pattern in its behavior. so confusing!
     
  8. Shadetreemechanic

    Shadetreemechanic Full Access Member

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    Half the FSV is always operating under negative pressure so it won't always weep when sucking air. I have never seen an FSV itself actually leak, its generally the oring quick fittings on the in and our ports.
    Working on the FSV is messy. You will be covered in diesel when its done, but if you are planning to drop the tanks you have already resigned yourself to get messy.
    Why don't you disconnect the valve. You can then test it by blowing air through it to check for clear flow in both positions, you can also put air back into the tanks to blow any obstructions in the pickups out, and then replace all the FSV orings and put it back together?
    If you hear the FSV click, then you know the motor works. that leaves you with debris keeping it from moving fully from one position to the other. Failed showerhead chunks can get into the fsv and cause flow problems, but usually a little air pressure from the other side can blow them out.
    It sounds like you are chasing the problem that parked it years ago, so at least its consistent.
    The other thing that no one has mentioned is clogged tank vent. You can test this by pulling the fuel caps off and driving it, but I have never seen one die within a couple miles of starting with clogged vents, that usually takes several miles of highway driving to show up.
     
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  9. foundonroaddead

    foundonroaddead Registered User

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    Great idea! I’ll disconnect the hose on the FSV and just use an air hose and see what it will blow out on both sides and back through the lines into the tank.

    Also, if you are aware, are the o-rings just a generic size like 1/4 or something else? And the fuel lines felt quite hard (30 years old after all) if they happen to break can i just replace it with plain ole rubber fuel line hose like what’s used on the return lines and such and crimp them with hose clamps?
     
  10. Shadetreemechanic

    Shadetreemechanic Full Access Member

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    Knock on wood I have never broken one of those hard lines. Take them loose from the frame clips so you have more room to bend them. I do think the o rings are standard. You will probably break a holding clip or two getting them off so pick up a pack of them. Dorman sells a bubble pack of them at most parts stores.

    If I were going to splice into the hard lines with rubber, I would do it with a brass barb fitting. You can heat those hard lines with a heat gun and they will soften so you can push a barb fitting on them. My fear would be that slipping fuel line over them would want to leak in cold weather because there is no texture to the hard lines.
     
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  11. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Just to add here. You want to make sure that there's two sizes in this pack and it's not just a pack of one size. I don't know if they're sold in packs of just one size, but I wanted to point that out.
     
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  12. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    I'm not a strong reader so maybe I missed some info but idles fine then dies while driving is a classic clogged fuel filter. In your case maybe the screen on the Facet, maybe the main filter under the hood.

    Not saying it isn't the FSV, could be junk in there too but the clogged filter has happened to me and it was infuriating for 3 days before I figured it out. In my case a little pre-filter on a cheap cube pump but same concept. If you have a fuel pressure gauge for a gasser you can use that to check at the filter header. The last port on the header towards the IP is the only one that reads after the filter. I can't remember what that port does currently as mine was deleted.

    Also for the hard lines if you cut into them just slip fuel rated hose over them and use a spring clamp, not a cheap screw type clamp. No leaks or air in over 10 years like this for me.
     
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  13. foundonroaddead

    foundonroaddead Registered User

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    Update: i took off the FSV, cleaned it down with brake cleaner, and blew compressed air into the 6 inlets, plugged it back in, switched the tanks, and blew it all out again. Couldn’t see much debris come out of it though. Then took the compressed air and blew into the return and sending hoses for each tank and well... i got myself a nice, refreshing bath in the process. i did hear some thunk sounds when blowing air into the lines, as if something fell to the bottom of the tanks. maybe knocked whatever was in there loose.

    then i put the hoses all back onto the FSV and turned on my electric pump and no leaks around the FSV as far as i could see. However, my pump kept struggling to pull up fuel. i put a tire gauge on the Schrader valve next to the fuel filter and it was only putting out 5 PSI max, then would get a little burp of fuel, fill up the bowl, reach 8-9 PSI, then drop back down after 2 seconds. the truck wasn’t even running.

    i have this one mounted next to the fuel filter in the engine bay and know most all these pumps are designed to push not pull, so i think i’ll mount it down by the FSV instead and see if the problem persists. if it does, i’ll just toss this facet somewhere and get a different brand all together.
     
  14. foundonroaddead

    foundonroaddead Registered User

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    this is quite funny. the rear tank before was working fine, and the front was sucking in straight air. now it seems the roles have flipped and the front tank sucks up fuel, albeit with a ton of air, and the rear seems completely dry. this is baffling.
     
  15. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Do you have the air purge off the header going to the #1 injector return line? If it's deleted the air won't really purge until you turn the key on with a cold engine. And it'll take a bit since you blew the lines out.

    Facet Duralift pull just fine, unless of course it's drawing air! But they do self-prime and are used on refer trucks 10' over the fuel tank, which is quite a bit more pull than our application. Move it if you like but at this point it's not going to be causing trouble.

    For troubleshooting you might just pull the supply line out of the FSV and put it into a bucket of fuel. Still drawing air? Your problem is downstream of the FSV. If it's good then FSV or upstream.
     

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