Forklift problems, runs 3sec. and dies
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  1. #1
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    I'm hoping one of you guys knows a bit about what I need to look for, how to fix it and are willing to share.

    We've got this forklift at work, its a clark about 6000lbs, I think the model #is 'officially abused and never maintained'. The cyclinders all need to be redone and the valves stick, but generally it works. All the wiring is mickey moused and the ignition and starter switch are hanging out the side.

    The current problem involves something I have no knowledge of, propane engines. It used to start and run good, and then it went to crap. When we mickey moused the wiring we bypassed the coil resistor, and after blowing two coils, added a resistor, this may or may not be part of the problem. Now there is no ignition bypass to put a full voltage to the coil on startup, this is just info on what has been done. Now to the problem, the forklift will start up, if its cold, but will only run for a few seconds, unless your constantly playing with the gas, then you might get a couple of minutes out of it, but once its started, its done for the day.
    I haven't done any research on this yet, I've been putting in 12-14 hours a day and the EMJ driver is getting a little sick of us pulling material off his truck with a tow strap, besides, we have some heavy shipments coming in that can't be dropped on the ground. I just haven't had the spare time.

    I'm guessing it is either a valve or a carb problem, the problem is, I have no background dealing with how propane goes from a liquid to a gas and through the carb. I guess I could have a tech(or whatever a forklift mechanic is called) come and look at it, but I figure, we do our own machine repairs, how hard can a forklift be.

    If any of you can help me get pointed in the right direction, I'll even post a pic of this 'piece of crap' so you all can laugh at it, it might even be worth scrap value?

  2. #2
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    This sounds like something that was happening to a forklift of ours.Called in the forklift repair company down the street & they had it fixed in no time.I believe it had to do with the carb but who knows if it's the same problem.Best bet is to call in a pro.

  3. #3
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    not being a jerk, i hope..

    did you try another can of propane? sounds like either low on pressure (or gas) and/or a "wet" can

    jeffe

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    I am betting you have a Clark 500 series with the Clark OHV engine and shuttle shift "rock crusher" transmission. That is high-low with forward and reverse. There is nothing electrical on those trannies.

    First, make sure the engine is full of coolant. If the vaporizer is not submerged, it will freeze up instantly. The vaporizer is an internal unit if the forklift is old. If it is a conversion, the vaporizer is in the upper radiator hose.

    Press the center button on the regulator when attempting to start. If no button exists, the unit is a modern electric only solenoid unit. Apply 12 volt when cranking and running. Clark has a surge system on the regulator when cranking. There is a wire from the 'R' starter terminal to the regulator center post. When running; the ignition feeds the regulator through an oil pressure switch. You must have the ignition on and two pounds of oil pressure to keep power to the regulator, after cranking.

    The carb is a simple unit and I doubt it is bad. Check the fuel filter. It is the brass screen before the regulator. Propane carries a gummy residue if it has been improperly refined. Carb cleaner and air pressure in reverse will dislodge the gum. A new filter is better. They are ten bucks.

    The ignition is pure Chevy from about 1959 to 1980. That means that you use all old GM parts, including the coil resistor. You better have 1.82 ohms resistance and the eight volt GM coil. It takes someone special to screw up an old Clark. Those green monsters were just this side of indestructable.

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  6. #5
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    Bob,
    It would be best if you could describe your propane system to us. There are a whole lot of different ways to get the LPG to the carb. You could have a separate vacuum or electric lock-off, your vaporizing system could be in the radiator hose or have lines routed to your vaporizer, etc. I work on one Clark that matches nothing in the books if I go by serial number. It's sister by serial number lives 100 yards away at another business and has the same problem.

    Since it's a 'piece of crap' you can't hurt much by pulling the line from the regulator to the carb and seeing if it'll run on ether.

    Something to think about. How much time have you wasted on this thing? That $75-$150 call isn't all that much in the scheme of things. Then again, I'm on the other side of the fence

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    my old reliable hyster kept cutting out,,I would get off and check the LP, etc etc then it would start again. Half hour later it would cut out again. this was happening all day, but I noticed eventually that it only happened when I was near a particular wise guy, who it turned out was turning my valve off and then turning it back on when my back was turned. ......

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    There's no magic to propane, you do all the steps in the corect order to troubleshoot them , then repair the defective part. However it should be done by a professional unless you have a lot of fire insurance.Shooting ether can also be dangerous.

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    Bob,
    If this unit is new enough to have Impco carburetor and vaporizer, check the back side of the vaporizer for a small hole (1/64"). This vent to atmosphere must be able to breath to let pressure from the tank pass. If it is plugged, the symptoms you describe will result. Just one possibility.
    Max

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    Thanx, I was at work all day today and didn't even look at it, however I did call back there on the way home and the co-worker said it is a model GCS-20MC made in 10/84. From the condition of it I'm surprised it isn't steam powered, I though it was about 10 years older.

    It does have a fresh tank of propane in it, that was the first thing we did when this started acting up. As far as time into it goes, not that much, about 20 minutes to mickey mouse the ignition, and had a part time college student do most of the other stuff that had to be done, with supervision of course.

    I'll take a good look at it Monday morning (I'm actually going to take a day off), and let you guys know what type of system it is so maybe you can help me get a little further along. As far as fires go, its in the middle of a sand and gravel parking lot, and if it burns the owner will have no choice but to buy or lease another one. Also as far as having a professional come look at it, we had one come out last year, they didn't want to touch it except for to completely overhaul it, which really isn't a bad idea.

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    Hi,
    Sounds very familiar!!!!! I have a Clark Gpx 2500. We have had a lot of problems with it. Here's what I discovered. We installed 1 new ignition module, halfway worked. Replace the distributor twice, second new one worker GREAT!! Unfortunately, two weeks later new module seems to have failed ( I think we didn't have the resistor in the circuit correctly. Just for fun, put a timing light on one of the plug wires and see what you discover.
    Best wished Jim.

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    Since this thread is only 7 YEARS old, I'm guessing Bobw got the forklift running by now, but he did not post an update to this thread.

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  14. #12
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    Guess I should look at the date!

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    Quote Originally Posted by flathead View Post
    Guess I should look at the date!
    Check the oil level first as some used a low pressre switch on the lockoff.

  16. #14
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    Here is the update, I haven't worked there for close to 6 years now. Never got that forklift running, flat out didn't care, it was a giant piece of crap, hotwired,
    no floor board, torn up tires. The boss at one point had someone that knows forklifts come and look at it, he laughed and threw a high ball number at it, more
    than getting a decent used forklift would have cost.

    Did a few little things for the cabinet shop across the street and he started to let us use his forklift when we needed it
    for free.

    From what my business partner said, that old forklift is still sitting back there, rotting away.

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    you should write a book on the old forklift

  18. #16
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    This is all good advise. I've always been surprised at how cheap fork lifts are at auction. More problems? maybe. But now we know what to check first.


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