Clark C500 SERIES:
Can't get propane running without primer button pushed in.

Can't get forklift running properly. Have to keep the primer button on the converter pushed in with a little stick to keep it pushed in in order to keep it running. I've replaced the converter with a new Impco Model J, but no difference. Then I took the mixer apart, and cleaned it out, it was very dirty with oil + dust buildup (Does the diaphragm have oil below it, so when you push on the diaphragm you get oil coming out of the 4 air passages?). Still no difference. Then took the lockoff valve off, cleaned out the filter with compressed air (had some small metal filings in there too), and put it all together, but still no change. The forklift is really old and doesn't warrant a mortgage. When I pushed in the diaphragm on the lockoff valve, I can get the machine to run , but I have to keep the revs up because when I let it go to idle it just dies. And then to start it up, I have to push in the converter primer button etc. and do it all over again. Anyone able to advise me on my next steps to try?
  • Posted 1 Apr 2008 06:45
  • Discussion started by ken_h
  • British Columbia, Canada
Ken_h
Showing items 1 - 3 of 3 results.
Sounds like maybe your throttle linkage possibly isn't positioned correctly. The big screw on the mixer that looks like it's made to be adjusted with a nickel is your idle mixture. Doesn't really effect your idle speed too much, at least not dramatically like your talking about.
I would start by inspecting the throttle linkage from the floor board back. Do you know if it's a Continental flat head or a Wackashaw? get me the truck's serial # - it either starts with 355 or 235. I forgot to mention- that the "oil" you saw in the regulator is typical- that's a by-product of "cracking"- when the fuel changes from a liquid to a vapor. Some requlators even have a drain valve to drain that gook out of there. stinks, doesn't it!
Try unhooking the linkage from the carburator (mixer) to eliminate linkage problems. Is there a return spring for the accelerator linkage?
  • Posted 1 May 2008 18:14
  • Modified 2 May 2008 03:19 by poster
  • Reply by larry_m
  • Pennsylvania, United States
Larry: Thanks so much for your help! I now have the machine running again, but it now it's running at super-high revs and I can't seem to get them down. I've tried adjusting 3 things: The rich/lean control on the top of the propane/air mixer, the huge screw on the side of the mixer which cuts off airflow from the hole inside, and I tried adjusting the position the linkage to the pedal holds on the shaft that runs through the carburetor/mixer (and thus positions the butterfly flap inside). All efforts came up with no change. I need advice from a guy like you with experience! Thanks again Larry.
  • Posted 5 Apr 2008 06:26
  • Reply by ken_h
  • British Columbia, Canada
Ken_h
Just because the convertor is new, doesn't automatically mean it's good. Double check the presure at the 1/8" pipe plug- should be 1.5 PSI. If it's good, sounds like a vacuum leak.Pushing the primer button makes it go full rich. Use carb cleaner to find the leak. Keep it running with your "little stick" and spray around the intake, throttle shaft and mixer gasket, if the RPM's pick up when you spray something- there's your leak. Dont give up on the C500! One of the best trucks ever made! Let me know how you make out- I'll try to help.
  • Posted 4 Apr 2008 09:09
  • Reply by larry_m
  • Pennsylvania, United States

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