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Thread: Bleeding a Perkins, is it really that complicated !?

  1. #1
    Seglare Sven's Avatar
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    Bleeding a Perkins, is it really that complicated !?

    So now that we know more about our fuel gauge, it is time to bleed the Perkins.

    I've just read the workshop manual and it seems way too complicated. It talks about unscrewing

    - the vent plug on the fuel filter

    - the head locking nut on the side of the fuel injection pump

    - the air vent screw near the top of the fuel injection pump

    - the pipe union coupling at the fue injection pump inlet

    - the unions at the atomizer end of the high pressure fuel pipes

    and then pumping fuel until no air bubbles come out.

    Since we have the electric fuel pump in series with the fuel lift pump it sure seems like running it for a while should clear most of the air out of the system with the possible exception of the last part, the high pressure fuel pipes.

    I've read on some diesel forums that you can also run a diesel of WD-40 (into the air intake) to lubricate the pistons while priming the system. Is that really a good solution ? I guess the WD-40 will burn just fine and drive the engine but it seems too simple.

    After fixing the manual pump tomorrow (at least ordering the part :-( ) I need to get the fuel system bled so we can calibrate the fuel gauge and fill the tank back up to head for Moss Landing and MBARI. Insights are appreciated, as usual !



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  2. #2
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    I have cranked many Perkins's in my time, and yes, that does seem a little too much. I have never once did this, that it wasn't a messy proposition. Plenty of "oil diapers" is the plan. Pampers work well in the absence of the "correct" oil absorbent pad.
    The top of the filters do need to be opened, because the air trapped in the top of them can't get out any other way. Then the line that connects to the injection pump should be loosened, and pump fuel through that sucker like you own stock in B.P. I can't see a reason in the world to break those unions. There's only one fuel line coming to the injector pump, and you're just purging the air. The return line doesn't matter HOW much air is in it, it just recirculates it back to the top of the tank. Warm fuel albeit. Diesels like hot fuel.
    You may have to go through the process of bleeding the high pressure lines at the injectors. That in itself can be a lesson in patience, but it's the only way.
    I don't know about the WD-40 in the intake. I've never squirted any in a diesel, so myself, I can't say "do it". Or not for that matter. Bearing in mind that this advice is coming from the same idiot that put laughing gas in his motor. But that old dog hasn't run in years, and in my exasperation, (read:damn fed up), with the cranking procedure, that by then it was, "I'll crank it, or blow this piece of junk to pieces". It eventually fired..
    Without ether..

  3. #3
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    Here is my generic procedure to bleed any mechanical diesel:
    1. Make sure the fuel filter is full, run the aux pump, etc. to do so.
    2. Hold "throttle" wide open.
    3. Crack all the high pressure lines at the injectors.
    4. If the glow plugs are easily accessible, remove them.
    5. Crank the engine, holding WOT, with aux pump on, until fuel is seeping at each injector/HP line union.

    Once there is fuel at the injectors, tighten up the lines again. Reinstall glow plugs if needed. Then run through the standard starting procedure. It should start. This procedure works for VW, Kubota/Universal, GM and Mercedes diesels and has never failed for me. YRMV.....

    I have also heard that diesels will start on WD40 but I have never tried it. Supposed to be less violent than ether..... You are your warranty at that point.

    RT
    Rob Thomas
    Wakefield, RI
    1983 Ericson E38 "Ruby"
    "I purchased a boat because setting fire to $100 bills was not an efficient enough way to dispose of them...."

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    Principal Partner exoduse35's Avatar
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    Yes RT, WD-40 does work as a starting fluid. It is actualy mostly karosene and scent. Your Method is almost exactly as mine and always works. I alow the glow plugs to cycle as I crank over the engine. As the cylinders bleed and you close themdown the first ones will begin to fire and releave the stress on the battery and starter. Asthe fuel lines are all diferent lengths (and thus volumes) there is either a lot of flouding to the first cylinders making it dificult to burn, or you can use it to help get the job finished. Edd
    Edd
    E 35-2 # 163 Exodus
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    IF the glow plugs come out there is little resistance for the starter turning the engine so that is why I do it. I hear you on the "tighten the lines that wet early" as yes they will begin to fire and help spin the engine. Actually, if an injector is suspect due to rough running, etc. any injector line can be "cracked" or loosened while the engine is running. If there is no change in engine smoothness or rpm that injector is not functioning correctly. Old mechanical diesels are some of the simplest engines to work on and keep running. I'd take a mechanical diesel any day over anything electronic or a gasser.

    RT
    Rob Thomas
    Wakefield, RI
    1983 Ericson E38 "Ruby"
    "I purchased a boat because setting fire to $100 bills was not an efficient enough way to dispose of them...."

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    Seglare Sven's Avatar
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    Close the cooling water sea-cock ?

    I think the answer will almost certainly be "no" both because of dry impeller wear and the possibility of overheating if it isn't opened soon enough once the engine fires.

    But, I worry about filling the water lift and getting back-flow while bleeding the high pressure lines ?

    I assume the lift pump does nothing to help bleed the high pressure lines and that only turning over the engine will accomplish that ?

    (BTW, a complete aside ... we now know that when the fuel gauge first reads zero we have almost 5 hours (gallons ?) left. When the gauge reads 1/4 we have 10 gallons.)



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    Absolutely, yes. You don't want to crank for very long or you will fill your waterlift.

    Disconnect the raw water cooling line where it enters the exhaust elbow, and let the water flow into the bilge while you are purging the fuel line.

    Closing the raw water seacock won't harm your pump impeller so long as it isn't run dry. There should be grease in your water pump which will lubricate the impeller. But it's probably better to do disconnect at the exhaust elbow.

    Which Perkins do you have? The 4-108? Those were a bear to bleed.
    Last edited by Steuermann; 08-28-2012 at 01:47 PM.

  8. #8
    Seglare Sven's Avatar
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    Quote Originally Posted by Steuermann View Post
    Which Perkins do you have? The 4-108? Those were a bear to bleed.
    Yes, 4-108.

    We have the electric in-line pump to help out but never having done this I'm basically walking through the whole process in my head, step by step, before starting anything that could cause cascading problems. So, thanks for the input (and all the earlier ones too of course) !



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  9. #9
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    The electric pump will help push fuel and trapped air through to the injection pump. This fuel and air will pass through the IP as the engine is cranked and escape at the injectors that have been loosened from their hard lines. This is the same concept as bleeding a brake system with a power bleeder only you have to crank the engine to have the IP cycle the fuel/air through it. That said, I just leave the seacock closed to keep from filling the waterlift muffler. Never had a problem with the impeller wearing out just cranking, make sure to open that seacock immediately if the engine starts to run! RT
    Rob Thomas
    Wakefield, RI
    1983 Ericson E38 "Ruby"
    "I purchased a boat because setting fire to $100 bills was not an efficient enough way to dispose of them...."

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    Ok, I just replied, but came back to my desk after grabbing a sandwich and saw it didn't post, so here goes again.

    The electric pump will help a lot. With the Kubota-based marine engines, you just turn on the pump, loosen a screw on the injeciton pump and bubbles are routed through the return line back to the tank. [edit: But you don't have one of those, so I don't know why I bothered mentioning that. You have an old-fashioned marine engine (a good one, though).]

    I presume the fuel pump is located between the fuel tank and the fuel filters. You can bleed all the fittings from the fuel filters to the injection pump, and perhaps farther, without cranking the engine by using the electric pump. I always bleed fittings one at a time, starting at the fuel filters. Depending on the type of fuel filter you have, there should be a plug that you can unscrew at the top of the filter to let air out. Loosen it until you get a constant stream of fuel with no bubbles. Catch the fuel in a rag. (No matter how careful you are, one thing is for sure, and that is the interior of your boat will never smell the same again!)

    Your installation probably has two filters. The first will most likely be a large pore filter/water separator, the one closer to the engine will be a fine pore filter. Bleed each one in turn, starting from the one closest to the electric pump and proceeding toward the engine. Each filter unit should have a small screw or pipe plug at the highest point on the top of the filter unit that you can remove to bleed air bubbles. Remove the first one, let the bubbles escape, tap on the filter to make sure no more bubbles are stuck to the filter element, then tighten and do the same with the next filter.

    When the filters are purged, move to the injection pump. There should be a bleed port on the top, or near the top (it's been a while since I've worked on that engine). Loosen it 1/4 turn and see whether the electric pump has enough power to force fuel through the pump through the check valves. If fuel and bubbles run out, wait until all the air bubbles are out, then tighten the plug.

    At this point you can try cranking the engine to start it. It _might_ start, but my experience is that it probably won't until you get the injection pump primed. You are going to have to start cranking the engine from here on. Loosen the connector at one injector 1/4 turn and crank the engine until fuel and bubbles, then fuel only, weeps out. Then with the engine still cranking, tighten the fitting. That operation should take no more than 5 seconds of cranking to accomplish. Repeat with connectors to #2, #3 and #4 injectors. While you're doing all this, one or more cylinders should fire which will help speed the process. Once the engine is running, unless it is running smoothly, loosen each injector line in turn, then re-tighten in order to evict the last few bubbles.

    If you have no luck, repeat. Always start with the fuel filters and proceed towards the engine. Never simply open all of the fittings or you will have a miserable time cleaning the mess. When changing filters, often a bubble will get hung up in the housing or on the filter element. I always connected a piece of hose to the engine side of the fuel filter and let the electric pump run quite a lot of fuel, usually a liter or so, into an empty milk jug. By the time that much fuel had been run through the filters, usually all the air was purged.

    Once you've done this, the next time will be easier. And you will make sure you never trust a dial-type fuel level gauge on a sailboat again. A sight tube is much more reliable.

    And make sure you take all your oily rags and dispose of them properly. Don't keep them below, even if there is only a little oil on them. They can ignite with surprising ease.

    Best of luck!
    Last edited by Steuermann; 08-28-2012 at 04:20 PM.

  11. #11
    Seglare Sven's Avatar
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    Thumbs up Many Thanks ! We have a running engine



    The Racor was still full of fuel so we could not have sucked in all that much air into the system

    I took the advice to turn off the cooling water intake.

    We ran the fuel pump for 30 minutes or more while I re-read the advice here and the manuals and started taking apart the cabinetry around the engine.

    I found that one flare-fitting in a fuel line leaked when pressurized by the electric pump. Slight panic when I couldn't get it to seal and then found that the flare was basically all gone ! The marina/yard here has no official diesel mechanic so I thought I was up a creek and I was about to call John for help. Then I talked to the yard manager (Erik or Eric) who's a really nice guy and he said that unofficially he's a mechanic (trained on aircraft engines). He made a new flare fitting for us on the spot and we were in business.

    Then I asked Nancy to crank the engine for 20-25 seconds just on the off chance that it would work ... it blew the 200 Amp fuse at the battery after maybe 15 seconds !?

    I replaced the fuse with a 300 Amp fuse and we started doing 5 second starts with me loosening one injector union at a time.

    It probably took 15 minutes but then we had fire in the hole and started rejoicing


    My hands don't even look filthy, we must have done something wrong

    So, our sincere thanks to all. We'll miss our departure day because of the late success and we're still getting the gelcoat done, but we are back in business !



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