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Curtis B.
Curtis B., service manager
Category: Heavy Equipment
Satisfied Customers: 18961
Experience:  30 years exp. with diesel engines, heavy equipment and forklifts, including lp forklifts
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I have a 1977 Hyster H50 propane powered forklift. We had

Customer Question

I have a 1977 Hyster H50 propane powered forklift. We had a cold snap recently and when I tried to start it once it warmed up to 30 degrees or so, it would fire but not run. I replaced plugs, wires, dist cap, rotor. Now, once in a while I can get it to start but it will only idle. If I try to rev it up it will die. Any ideas? Propane system was working fine before the cold snap, but could the vaporizer be the culprit? Any problem with ditching the propane and converting to gas?
Submitted: 3 years ago.
Category: Heavy Equipment
Expert:  Curtis B. replied 3 years ago.

curtis b :

Have you changed propane tanks? Check the connection on the forklift, the female connection that goes on the bottle should have no gaskets or o'rings in it. It should only have a shiny stem that will go into the bottle connection. The seals are all in the bottle. If you have anything that keeps the bottle from fully opening, the unit will no recieve enough propane to run above idle. Also check the propane filter, it could be plugged or have frozen moisture in it. You will have a filter at the hose coming from the tank, going to the vaporizer or the filter will be in the vaporier inlet side. Converting back to gasoline is not something that needs to be done. The propane can be made to start easly and burns much cleaner than the gasoline. Let me know. Thank you.

Customer :

It does seem logical that it might not be getting enough propane. It does not have a filter but I was considering taking off the vaporizer and cleaning it. However, it seems to be getting propane everywhere. What confuses me is that when I squirt just a little starting fluid in the intake, it won't fire at all. If I've got good spark, shouldn't it fire on starting fluid? I seem to have good spark, but could the coil be a problem?

curtis b :

The mystery of propane is you can't see it! When you spray starting fluid in it , you are actually flooding the engine with too much fuel, so it will not run. The unit will have a filter, it will be on theiinlet of the vaporizer on the side where the hose comes from the tank. Did you examine the hose connection as I discribed? Fuel will be the problem, not the coil.

Impco VFF30 Vacuum Fuelock Filter
Full Size Image

curtis b :

The vaporizer pictured, Is the fuel lock and filter built into one unit. You remove the cover on the inlet side to expose the felt filter.

Customer :

I'm not looking at it right now, but propane line from the tank initially goes into what I believe is a separate fuel lockoff, then to the vaporizer which looks most like the Impco model J series. Connection from the tank to propane line appears to be correct as you describe. I believe that the propane line going into the vaporizer goes into the top.

Customer :

Does the Impco model J series have a built in filter than can be cleaned/replaced? If the propane tank is at an angle for a long time (hood left up in cold weather) so that it isn't level, can that affect the fuel flow?

curtis b :

The first item will be a filter lock/vaporizer, the second item Model J is the regulator , it has no filter in it. The only thing that leaving bottle at an angle affects would be whether it lets out vapor or liquid. A forklift should have a tube on the inside of the bottle that lets liquid flow to the vaporizer. If the tube is not under the fluid level, it will expell vapor. The lift will run on either, but power is less with the vapor.

Customer :

Okay, so I'll take the filter lock/vaporizer off, take it apart and clean it. Should I also do so with the regulator (it's actually a model J--see photo)?

Customer :

It's got two water lines going into it so I'm not sure how messy it would be to take off and take apart; however, I'm willing to try anything at this point.

Customer :

Full Size Image

Customer :

Full Size Image

Customer :

Full Size Image

Customer :

Full Size Image

Customer :

First image is regulator

Customer :

Second is fuel lockout

Customer :

Third is back of regulator

Customer :

Fourth is carburetor.

Customer :

Line goes from propane tank, to fuel lockoff, to regulator, to carb (or mixer?)

Customer :

I see that there is a little line going from lockout to base of carb; I guess this is a vacuum line.

curtis b :

Great pictures, yes the small line is the vacuam line. One thing that I haven't mentioned is the mixer (carburator) it has a diaphragm in the top of it, it can be bad, but usually if it is, you have a no start.

Customer :

I have had the top off the mixer and looked at it...if the diaphragm is bad, would it be obvious to me looking at it?

curtis b :

Yes, it would be obvious. If all else fails, I would replace the Model J regulator, a better replacement is the Cobra model.

Customer :

Is it worth taking the model J apart to see if anything is wrong?

Customer :

Would a Cobra require any other modifications to the system (aside from possibly where the hoses/lines attach to it)?

curtis b :

The model J and the cobra look the same on the outside, the difference is on the valving internal. I don't recommend rebuilding a J , with the prices for new unit running less than $100.00. Its just not worth the trouble. No modification is necceasary to fix in the cobra. Or you can still buy the J, they just don't last as long as the new cobra.

Customer :

I have purchased and installed a new vaporizer and lockoff. No change. I'm not surprised because I took the old ones apart and they looked really good.

Customer :

I have new ignition parts. I have spark. I have compression. Carb diaphragm looks good. I've even bypassed lockoff and ran propane directly to vaporizer/regulator. Behavior is always the same. Forklift fires but won't start, or if it does start, it will only idle poorly.

Customer :

Is it possible to get a bad tank of propane? Aside from that possibility, I'm beyond stumped.

curtis b :

One thing that hasn't been looked at is the timing of the unit. Have you tried moving the distributor to see if it makes any difference. I think this old ford engine has timing gears and not a chain, but it still could be out of time. I had a thought, the model J has a spring loaded pin the the center of the cover, does this spring pin have any tension on it ,or is it hard to push? I would assume by now that you have tried a different bottle of propane. If you loosen the propane line at the lockoff, do you get fuel under pressure?

Customer :

According to our timing light, the timing is correct.

Customer :

Spring loaded pin is very hard to push, which I'm assuming is a sign that there is good propane pressure.

Customer :

I do get fuel under pressure.

Customer :

I guess my next step should be to try a different bottle of propane. I have not done so because I don't have another and live in the middle of nowhere, but maybe I could borrow one. I think there's one other propane powered forklift in the county.

curtis b :

Pin should be easy to push! Usually if pin is hard to push, the regulator is not working. Try turning off the propane bottle and see if it will fire, then just barely open the propane bottle to see if it makes difference.

Customer :

I'll try this later today when it warms up a bit.

Customer :

The pin on the old regulator pushed hard too when under pressure. They both push easily when they are not under pressure. Could diaphragm in mixer be bad even though it looks okay?

curtis b :

The diaphragm could be bad, they can have pin holes that are hard to see. The pin the the center of the regulator should be fairly easy to push, if will give a little extra shot of propane when it is pushed. If it hurts your finger to push it, there is too much pressure on the inner parts.

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30 years exp. with diesel engines, heavy equipment and forklifts, including lp forklifts