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Thread: H-1 Ground Support Heater, NSN 4520-01-056-4269

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    4 Star General Wire Fox's Avatar
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    Default H-1 Ground Support Heater, NSN 4520-01-056-4269

    I just brought home an older ground support heater, NSN 4520-01-056-4269, manufactured by Davey Compressor Company of Cincinnati, Ohio. It's definitely a bit rough around the edges, but it looks like all of the essential equipment is there and in-tact. The hour meter reads out about 1400 hours, so it seems that it was rather well-loved in its day. Also a nice perk is that when the seller got it, there was a twin also being discarded where the other recipient only really wanted the trailer, so he took most of the other equipment off of it-leaving me with a spare control panel (including the regulators mounted to the under side of it), spare diesel engine, and spare blower assembly. Not a bad deal for all of this at less than the price of single small engine!

    I can't find the exact manual for this unit, but have found similar ones that will definitely be helpful on their own; however, if anyone has this manual/T.O., I'd really appreciate it. It should be T.O. 35E7-2-11-11.

    This unit appears to use a single shaft-driven fuel pump & fuel filter for both the engine and combustion chamber (if I read it correctly, some similar models seem to indicate having a separate v-belt driven pump for the combuster). Another thing that seems to be different is the trailer chassis and speed rating: most look like they have a sort of of U or O-shape chassis, but this is a more traditional ladder frame. As well, the wheels are pretty typical to the average small trailer I've seen, the "tow bar" is a nice, full-length trailer tongue that doesn't fold or slide, and there's marking on the trailer indicating a top speed of 50 MPH-much better than the 20 MPH most trailer-mounted H-1 heaters are rated for! As for obvious defects, I've already encountered several cracked O-rings. Without a manual, I know I'm going to need to learn to measure o-rings correctly and pay a visit to my local supply house to replace these one-by-one. As well, to be expected, the fuel is positively bad that's sitting in the tank. I need to drain it all out, clean the tank, try to purge the lines, and change the fuel filter prior to trying to start this.

    Oh, and this heater also already helped educate me on what an "oil bath filter" is. I went to check the air filter, expecting to have a dry element or a lightly-oiled foam filter, but then had the bottom drop out and spill oil all over my leg and the floor...oops. After doing some googling to see an example of that filter and realizing that it was meant to be that way-not some odd backflow of oil into the air filter-I accepted that I was just an idiot and proceeded to throw my pants in the washer.

    Here's the data pulled from nsn-now:
    MOUNTING TYPE TRAILER
    HEAT MEDIUM TYPE AIR
    CIRCULATED AIR TYPE HEATED
    WIDTH 55.000 INCHES NOMINAL
    CURRENT TYPE DC
    DEPTH 70.000 INCHES NOMINAL
    PRIME MOVER TYPE DIESEL ENGINE
    CURRENT RATING IN AMPS 35.0
    HEATING ELEMENT TYPE BURNER
    IGNITION METHOD ELECTRODE
    HEAT DELIVERY RATE 400000.0 BRITISH THERMAL UNIT
    INTEGRAL FUEL TANK CAPACITY 24.5 GALLONS
    VOLTAGE IN VOLTS 24.0
    FUNCTIONAL DESCRIPTION DESIGNED FOR PREHEATING AIRCRAFT ENGINES,COCKPITS AND CABINS WHERE THE AFCT OPERATE IN ARCTIC REGIONS
    FUEL TYPE JP-4 JET FUEL AND JP-5 JET FUEL AND DF-A ARCTIC DIESEL FUEL OIL AND DF-1 WINTER DIESEL FUEL OIL AND DF-2 REGULAR DIESEL FUEL OIL
    HEIGHT 42.000 INCHES NOMINAL
    REFERENCE DATA AND LITERATURE AF TO. 35E7-2-11-1
    SPECIFICATION/STANDARD DATA 81349-MIL-4607 GOVERNMENT SPECIFICATION
    NONDEFINITIVE SPEC/STD DATA 4 CLASS
    UNPACKAGED UNIT WEIGHT 734.00 POUNDS


    Will edit soon to mobile upload some pictures... Including the seller's photos right now. Edit 4: there's my pictures I took this morning!

    EDIT: This thread is the same unit as mine. The engine P/N matches up, too: https://www.steelsoldiers.com/showth...r-Trailer-Help
    Another EDIT: Found a document from Hatz-Diesel that gives specs like oil type, volume, temperature ranges, torque specs, and tolerances for the various engines. Assuming I'm interpreting the P/N correctly, this would be a variant of their E-673 engine, which has a full set of specs in the attached PDF.
    Edit 3: Found a parts manual that helps my case on the P/N format (LN is a sub-option), plus I also found a repair manual the covers the E-571, 671, 572, 672, 573, and 673 models. I've got the part manual uploaded, but the repair manual won't go through for some reason. I'd be happy to email this to a MOD if they can add upload it for me...
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    Last edited by Wire Fox; 04-26-2019 at 12:03.
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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    4 Star General Wire Fox's Avatar
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    Alright, so I've gotten a start on getting truly hands on. Drained and rinsed the tank with some fresh fuel, changed the engine oil (well, it had no oil. I just ended up filling it), and attempted to change the fuel filter unsuccessfully (more on that soon...). Slaving off of my HMMWV and following the operating instructions on the data plate, I got it to fire right up! The engine roared up to life pretty quick and seemed to be going well, but started surging and eventually would slow and die. I could immediately restart, but it would slow and die faster, the less it sit.

    I popped off a fuel return line to see how much girl was getting back and it was a pretty substantial volume. I filled a pint container in under a minute, stopping with the engine starving and dying. With that much fuel on the return from the engine's injection pump, it doesn't seem like fuel pressure and volume should be the issue...

    That said, I found it suspicious that the fuel filter installed is a PH51A oil filter. I've been very unsuccessful in finding a suitable replacement filter actually rated for fuel use (with water separator) that can fit in the space. The 8" filters are just barely too long... If you think that an oil filter can actually work in this role, let me know. The PH51A at least does not have a bypass. It's M18-1.5 thread size makes it harder to buy substitutes... http://productguide.luber-finer.com/...l?partNo=PH51A

    As well, I'm trying to learn how to service those oil bath air filter. I recognize that it's entirely possible that my actual problem is this air filter being clogged, but I can't figure out how to remove and clean the packing material after I have the oil bath can removed, at least without seemingly destroying the fiber. I'll be digging around YouTube and some similar engine repair manuals trying to figure this one out. Until then, I'd appreciate some tips!

    Sent from my Nokia 6.1 using Tapatalk
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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    You need to join the forums at Bob Is The Oil Guy, those people will climb out of the woodwork with all of the answers you need. Iím afraid I canít offer any help but Iím very interested to see where this goes. Thank you for sharing that with us.

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    4 Star General Wire Fox's Avatar
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    What to do with the air filter is straight out of the Hatz Repair manual:

    Remove oilbath-airfilter by unscrewing fixing nuts on airintake flange of cylinder head. Do not tip oilbath-airfilter after removing since filter oil would run into filter element. When starting the engine this oil would be sucked into the engine and cause a dangerous increase of engine speed and thus might damage the engine.

    For cleaning remove oil tube by opening clips. Remove dirty oil and clean tub thoroughly with fuel. Fill clean oil up to mark "a" on the tub.

    Rinse detachable filter element thoroughly with fuel. Do not reassemble filter element immediately after rinsing but allow fuel to drip out for 10 minutes. Clean air-intake apertures carefully. Also the non-detachable filter element in the oilbath-airfilter has to be cleaned from time to time by repeated dipping and rinsing of the upper part of the filter in fuel. Wait 10 minutes in order to allow fuel to drip out.

    Note:
    The engine life is dependent on the proper maintenance of the oilbath-airfilter, which is therefore of particular importance. A neglected oilbath-airfilter causes premature wear since unfiltered or insufficiently filtered air is sucked into the engine. An oilbath-airfilter without oil in the oil tub is absolutely useless.

    The exhaust silence can be detached by unscrewing the fasting nuts and the corresponding flange on cylinder head.
    In short, sounds like I need to actually pull this off the engine to get a clearer picture of how to disassemble the filter, as there should be both a removable and non-removable filter element-I'm likely hung up on the non-removable element, plus I saw that there definitely was already oil in the filter, so that needs cleaned regardless.

    As to the advice on checking out bobistheoilguy, that's a great idea! I've read many discussions over there and know that they can get quite in-depth, so they've very likely to be able to help!
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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    4 Star General Guyfang's Avatar
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    This thing is Air Force equipment. I have looked everyplace I can think of, and can't find a TO for it. There has to be someplace that keeps this sort of TO. As long as it's for public release, it should be available. I will try an Air Force tech guy in Ramstein in the morning. I don't have his email, and it's 24:00 now.

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    4 Star General Wire Fox's Avatar
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    Quote Originally Posted by Guyfang View Post
    This thing is Air Force equipment. I have looked everyplace I can think of, and can't find a TO for it. There has to be someplace that keeps this sort of TO. As long as it's for public release, it should be available. I will try an Air Force tech guy in Ramstein in the morning. I don't have his email, and it's 24:00 now.
    You're the best for taking the effort to look for that, even if you end up not turning up anything.

    I did find an army TM that covers another piece of equipment that uses the same engine. It's been helpful at understanding some of the operations of the engine that weren't covered in any repair manual yet. Still, none of these adequately cover diagnostics of the combustion system and proper testing values of the various electronics on it. The data plate still does show me what each testing point's fuel operating pressure should be, so that's a small relief...

    Liquid fuel transfer pump:
    TM 10-4320-310-14
    TM 10-4320-310-24P

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    Last edited by Wire Fox; 04-30-2019 at 16:15.
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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    4 Star General Wire Fox's Avatar
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    Nice! While looking for information about the fuel pump, I stumbled upon the patent for the exact heater I'm working on. Funny enough, the patent literally expired today. https://patents.google.com/patent/US4276018

    The attached PDF has multiple detailed drawings and the dialog of the patent very clearly explains the operation of the heater and how one component interacts with the next. This is going to go a long with helping me trace out the problems in the unit...

    In a sad twist, Suntec/Sundstrand is informing me that I'm SOL on the fuel pump, as the model on there is very obsolete and they state there's no parts (including gaskets and filters) available, plus there's no direct replacement available. I'll probably still give their current J-series parts a try, as I bet that they're more similar than they let on, plus I think my main focus will need to be on the Bosch injection pump.

    EDIT: I think I may have figured this out. Reading the description in the patent, I can see that all of the fuel is going to pass through the main fuel pump (the injection pump does not do significant self-draw, like I've come to expect with larger pumps). With the heater de-engergized, all of the fuel it pulls is going to dump through the bypass line, which is pushed to the injection pump and any excess returns to the fuel tank. When it heater is energized, a solenoid opens, allowing fuel to both be pushed to the injector for the burner and to send fuel to the injection pump on the engine (plus dump any excess). In testing, I find that running for several minutes will eventually lead to the engine slowing down from apparent fuel rate loss and will stall. If I turn the burner on, the engine will almost immediately begin this process and will begin to fail rapidly. Switching it off can sometimes save it for a few moments before requiring a restart. If the system has a few moments to settle while off, it can easily start and run again for a couple of minutes without any repriming-the lack of repriming makes me think that it's not air intrusion, though this is at high risk of that due to age of the soft fuel lines. My hypothesis is that I have obstructions in the fuel pump's internal filter. As the system runs, the obstructions are picked back up and gradually jam the filter again, ultimately leading to its failure. Lack of pressure allows the worst of the sediment to fall and thus the engine can restart again. Now, this could also just be an improper main filter on my part that has too low of a fuel rate. The best that could be located expediently was a FRAM PH3980, which is supposed to be a 20 micron filter with anti-drainback and no bypass. There is no water separation capability, but the GPM is relatively low at 3 GPM for engine oil, which may be restricting the engine since diesel pumps always work with an excess of fuel.

    I will inspect the fuel pump's filter for substantial contamination and clean it as best as possible due to no replacement being available and check for performance improvement. Failing that, I will source a more appropriate fuel filter that should be able to guarantee proper flow. Failing that, I will replace fuel lines. Lastly, I will inspect the fuel injection pump. If that can't get this engine to run reliably without losing power, I have no idea what will. Once the engine is running, then I can focus on getting the burner's injector and igniter system working properly-then finally on to repairing the alternator's charge system and re-calibrating the output thermometer.
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    Last edited by Wire Fox; 05-01-2019 at 12:31.
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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    dumpsterlandingfromorbit! gimpyrobb's Avatar
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    I may have one of those fuel pumps, let me do some digging.

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    4 Star General Wire Fox's Avatar
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    Quote Originally Posted by gimpyrobb View Post
    I may have one of those fuel pumps, let me do some digging.
    Let me make sure I actually need one first before you dig too hard. I have a chance to turn the wrenches again tonight to check it. I also have a proper fuel filter arriving tomorrow I'm case it's not the pump.

    Sent from my Nokia 6.1 using Tapatalk
    1994 M998A1, 2-dr, 6.5L GEP NA

    Checkout my build thread! http://www.steelsoldiers.com/showthr...ild-in-Indiana

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