air in fuel line problemI

Discussion in 'Diesel Tech / 24 volts' started by Paraglider, Dec 4, 2016.

  1. Paraglider

    Paraglider

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    Some 40 series guys suggested I post this on this forum.

    I have an HJ47 late model 1982. A quick history if that helps understand what might have caused the problem now: The truck was sitting in Washington for 8 months, started a couple of times there but never really driven. I had it towed to Gary Mudrak in Sonoma. He did some work for me. When I went to leave, there was some air in the fuel line that he bled and then it seemed to run fine. I drove it for about 1.5 hours and it died. Bled the fuel line at the filter like he did. Ran another couple hours. This repeated itself several times down to San Diego. The last leg, though, lasted about 4.5 hours w/o any problem. It died as I was pulling into my driveway. I bled it and drove it about 2 miles the next day. I then left to go out of the country for 2.5 months (previously planned trip). Was not driven during that time. Came home and had to bleed it to start. Would run for a couple minutes and die. Repeat this 5-6 times and that's the way it is today.

    Here's what I have done so far:
    1. replaced the secondary fuel filter (not the water separator).
    2. replaced the primer pump with a Bosch.
    3. checked the fuel line back to the main tank and couldn't find anything obvious.
    4. checked the switch valve (auxiliary and main tank--see photo)

    Here's what I haven't done:
    1. isolated each element in the link (the primer pump/fuel feed pump, injectors, injector pump, switch valve, primary filter--water separator). At one point, the injectors were bled. There's no fuel leaking around the injectors or injector pump where fuel enters or at the primer pump.
    2. tried replacing current fuel line with clear to see if there is air visible and where it starts.

    Here are a couple questions:
    1. If I run fuel directly from a pail to the injectors, would that work without having any pressure in the line? I'm not familiar enough with this engine to know what I can isolate easily and what I can't.
    2. The primary fuel filter/sediment/water separator is very old. I don't see any pin hole leaks but not sure I would and I haven't dismounted it to try to look on all sides. Today, I replaced the clamp on one of the lines because there was a hint of very very slight fuel leak (glimmer at end of hose and about 1/2 inch fuel damp at the bottom of the hose. This is in the last pic. I don't yet have a replacement filter for this to try.
    3. I haven't followed the lines that have two bolts in them but would anyone know w/o that info. what these two lines might be going to or coming from or what it means?
    4. Should I be concerned about the kink in the fuel hose that feeds the auxiliary tank?

    Thanks for any help! This is frustrating and time consuming. :)

    20161203_155925.jpg switch valve

    20161203_151953.jpg fuel line from the auxiliary tank (don't think it's a return line)

    20161122_052048.jpg bolts

    20161203_152328_001.jpg kinked hose

    20161122_045532.jpg partial pic of the fuel filter; the one line hides the other behind it
     
    Last edited: Dec 4, 2016
  2. Squash

    Squash SILVER Star

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    My first step would be fuel from a clean source to the IP, once the engine runs smoothly move back towards the tank testing all fuel line components individually and replacing as required.
    It does not take much for a line or component like a filter to suck air.
    By all means use a length of clear hose between IP and filter as your visual aid and helper.
    Thing about diesel engines is that most IP's suck fuel from the tank, therefore leaks are tough to see because air is being sucked in rather than fuel being pumped out like a cut artery.

    IF you have to bypass filters then do so....they sell new ones!
     
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  3. mudgudgeon

    mudgudgeon

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    Was it running smoothly before dying? Or rough and stumbling at times?

    If it was stumbling, try replacing the last rubber hose before fuel enters the IP with 3' of clear hose . loop it out of the hood so you can watch it while uoi drive. Air bubbles will be readily visible.
    On the suction side, if a rubber hose is weeping fuel replace it.

    I've had a loose fuel filter letting air in cause my diesel to die with no warning. Prime the system and all good, then suddenly die.
     
  4. doug720

    doug720

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    Agree with above, and change all the hoses on the suction side at a minimum, and I would change them all, as many look original and/or in poor condition.

    Make sure the new hoses are diesel compatible, the correct size, and clamp with good clamps. I like to double clamp suction side hoses.

    Look for any diesel "Seeps" on filters, separators, connections, banjo fittings - hollow fittings that hoses connect to that use special hollow bolts to attach to injection pumps, filters etc. These use copper or aluminum washers to seal. Again look for seeps.

    This can be frustrating, but something is causing it to loose prime, and it's likely some connection or hose.
     
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  5. handcannon

    handcannon

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    For my Nissan SD-22 a Wix 33972 fuel filter has been recommended. The picture I have shows it as a clear case in-line type of filter with a screen instead of a pleated paper filter. I have never used one, or tried to find/purchase one, so I don't have experience with it. But, the information I have on it has-- Style: fuel filter (complete in-line), Type: full flow, Media: plastic mesh, Burst Pressure: 58 PSI, Max Flow Rate: 1 GPM, Nominal Micron Rating: 50. So, to me it sounds like it would be a good one to use while chasing down your air problem. It may be possible to not use a filter while chasing down your air problem, but it is also possible that you could dislodge junk somewhere that might create additional problems in your IP.

    As both Squash and mudgudgeon are saying, finding places for air intrusion can be difficult. Since it is not uncommon for the fuel lines to have a negative pressure (vacuum) for air to intrude without any visible external fuel leak. That is why starting up next to the IP with an alternative fuel source, and new fuel lines, is very important, and work your way back towards the fuel tank until you start seeing air bubbles in the clear line. If at all possible, when the fuel line barb is long enough, use two clamps together at each connection. This can help eliminate invisible air intrusion.

    Keep us posted on your progress/questions.

    Don

    PS- If that picture of the kinked fuel line is a filler neck supply (I think it is), then I would not be worried about it. It will only be possible for it to slow down the filling of the tank. It is something I would address sometime in the future, but it is not your air intrusion problem. Also, it looks like a radiator hose. I don't know about diesel, but gas in contact with a radiator hose will destroy the hose. The hose WILL soften up and be destroyed by the gas (personal experience).
     
    Last edited: Dec 4, 2016
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  6. roscoFJ73

    roscoFJ73

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    Looks like the PO did a rough job on the aux tank install. What/where is the fuel filter bolted to? It only has one bolt holding it on. Or is it a sedimenter?

    That one looks like a breather hose for the filler if that's the filler neck next to it.
     
  7. Paraglider

    Paraglider

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    When it was running after the initial bleed, it ran smoothly and does after almost all bleeds (probably on a couple the air wasn't really bled out completely).
     
  8. Paraglider

    Paraglider

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    Thanks (to all) for the comments. I will follow everyone's advice to use clear lines starting from the IP primer (That's the first place flexible lines are used.) and go back and use double clamps where possible. And yes, the kinked hose is part of the filler neck. Glad I don't have to worry about it in the near term.
     
  9. Paraglider

    Paraglider

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    the primary filter (sedimenter/water separator) is bolted by one bolt to the chassis. I'm planning on switching out that filter and using a Delphi 296 with a glass bowl (which I have already) but I had a tough time finding the right nipples (thread size). they should be on their way, though. I'd like to keep the fuel filter light possibility but all I can find for replacements that have a water sensor are REALLY expensive, so I figured I'd just look at the glass bowl occasionally and see if there's water.
     
  10. roscoFJ73

    roscoFJ73

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    Ok ,that clears it up. The sedimenter/water separator is not a filter , it just a place where water can be trapped until you empty it. The primary filter is the one on the fuel pump. Have you emptied the sedimenter out? I wouldn't rely on the light to tell you its full.
    The Delphi 296 is a great piece of work. Its cheap, the filters are cheap ,its compact and durable. I had one on my 1HZ into FJ73 swap .
    If the sedimenter is working ok ,there is no reason why you cant keep it, but I would secure it
    When things are sorted out ,you may also consider adding a pre filter. Its a larger micron filter that stops most of the junk reaching the primary filter.
    If it gets clogged up you can ditch it and keep driving or put another one in .They are cheaper than a primary filter.
     
  11. Paraglider

    Paraglider

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    okay. I thought I had read somewhere that called the sedimenter the primary filter and the other a secondary but I probably misread it. I have taken off the small bolt at the bottom of the sedimenter and let it run for a bit. It seemed like only diesel was coming out, so I put the bolt back in. I doubt it emptied the whole thing because the fuel doesn't just run out. It's a fast drip mostly with an occasional small stream. Does that mean something? The filter I put on it (the one connected to the injection pump) is a Wix 33393, supposedly good to 10 microns.
     
  12. John Galt

    John Galt

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    The primary filter is the screen on the fuel inlet pipe in the tank; it can get clogged with crud.

    There's another filter screen in the banjo bolt on the inlet side of the fuel feed pump that can also become clogged with crud.

    The sedimenter may have crud and corrosion in it if a steady flow of fuel isn't coming from the drain hole.

    Remove, disassemble and clean.

    On my truck I removed the screen in the tank and added an inline primary filter between the sedimenter and the fuel feed pump.
    On the BJ74 the sedimenter is in the engine bay where it can be easily serviced.

    Wix 33972 / Napa 3972 diesel Fuel Filter

    [​IMG]
     
    Last edited: Dec 5, 2016
  13. Paraglider

    Paraglider

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    John, thanks for that info. If the truck runs fine for 2-3 minutes before it starts stumbling, would that indicate that crud in the filter or on the filter screen in the banjo bolt on the inlet side of the fuel feed pump are not the primary issue?
     
  14. roscoFJ73

    roscoFJ73

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    The primary fuel filter is the big one in the engine bay. That's why the little one next to it is called the "pre filter" if you have one.
    The gauze on the fuel pick up maybe the first line of defence but its not really a filter.
     
  15. Paraglider

    Paraglider

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    It's a good day today! I had one small but important victory--thanks to your guys' advice. I disconnected the fuel line where it meets the primer pump, connected a clear hose from my diesel canister, primed it and it started right up and ran so nicely for about 11 minutes before I stopped it, restarted and it ran just as well. So I know that everything from the primer pump forward is working as it should and am super happy about that. If that's my only Christmas present, I'll be happy. :)

    I have two sets of questions, though. I'll treat the one first and then will post the other right after. In the pics I'm going to attach, what I don't understand is that after I primed the pump (and it primed pretty quickly and became much more pressurized than before, the whole clear hose didn't fill. It looks like there's a large area in the hose where there's no fuel and no matter whether I lifted the canister up (for gravity), it stayed in the hose. But the fuel level in the clear line before the primer pump almost never varied from its initial level (meaning, even though it doesn't appear to have fuel in the clear area of the hose, a tiny amount must have been being sucked through anyway, I guess). My question is why did the air get in the clear hose in the first place and why does it appear to not have a negative effect on the running of the engine (I mean the technical reason why)?
    The second related question is, how does this differ from if I have air in the line that stops the engine--will the air look different (like little bubbles in the fuel vs. a stretch of fuel line that appears to have no fuel in it--like I had here yet the engine didn't miss a beat)?

    thanks again for sharing your knowledge.

    20161206_071404.jpg

    20161206_071410.jpg

    20161206_071419.jpg
     
  16. John Galt

    John Galt

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    Let's focus on solving the problem not on semantics.
     
  17. John Galt

    John Galt

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    Pull suction on the fuel line that runs from the fuel feed pump to the tank. If there are no blockages then fuel should flow freely with little suction.
     
  18. Paraglider

    Paraglider

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    John, so from the feed pump, it goes to the sedimenter, I think, and then it goes to a manual switch that supposedly goes between the main and auxiliary tanks. So there's no clear run from the feed pump to the tank. My original plan was to put clear lines between the sections to see where the air is entering but given the fuel lines from the sedimenter on to the tank look like they're original lines (so 34 years old), I just figured I'd replace them with new fuel lines, replace the sedimenter probably, and see what happens. Does that sound reasonable?
     
  19. roscoFJ73

    roscoFJ73

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    I mentioned the (unlikely) case of having a vacuum in the tank. An easy test for that is to leave the fuel cap off so air can get in easily.

    Ive had my own drama yesterday of air in the lines from a faulty hand primer/filter head. At the moment I have by passed the primary filter and I am using only the pre filter.
    I diagnosed it with clear PVC hose
    When I can get a video uploaded I will show you just how much air it can take before it stalls.
    When the air is entering in the fuel lines it moves around a fair bit,it doesn't stay still like you described.
     
    Last edited: Dec 6, 2016
  20. roscoFJ73

    roscoFJ73

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    Normally fuel would run from the tank to the sedimenter. Then to switching solenoids then to primary fuel filters and then the injection pump.
    I would try and find the leak before adding any new fuel line.
     
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