Yale G83P-040:
Propane fuel system problems and Velocity Governor question

Yale G83P-040
Chrysler slant 6 engine

Velocity Governor question*

Propane forklift started running rough and stalling, restarts got harder and longer till
the thing would only just fire a couple times but not start up.

Had an old BEAM regulator and carb.
Since I got the machine 3-4 years ago, I knew the regulator had problems because
when you turn the key 'on' the fuel solenoid clicks, and you could hear propane hissing
into the carb....even before the engine is running.

SO.....got a new IMPCO regulator and carb, installed and mounted.

STILL does the same thing with these new parts, although, it does idle and will
rev up, but starts a lean out trend over 20-30 seconds and then stalls.

Sometimes it seems rich enough and revs up crisply, and idles, then it 'goes lean', runs rough, stumbles and eventually dies after 20-30-60 seconds.

There is a velocity governor under the carb........

* My key question is, HOW DO THEY FAIL ?
Is there a diaphragm inside that can break and let in a giant vacuum leak?

Seems like there is an intermittent lean out condition going on here.
  • Posted 21 Nov 2012 09:35
  • Modified 21 Nov 2012 10:07 by poster
  • Discussion started by dkmc
  • New York, United States
Showing items 46 - 55 of 55 results.
OK, if you are disconnecting the liquid hose BEFORE it enters the regulator/vaporizer you should get LIQUID fuel out when the lockoff solenoid is energized. That part of the hunt is not a defective condition. The fuel is supposed to be in liquid state when it enters the regulator/vaporizer.
What kind of hose do you have that leads the vaporized fuel to the mixer (part you are calling carb)?
Unless that hose is rated for LPG service, the inner hose liner layer might have swollen and is now unable to flow the volume of fuel needed at higher RPM and power demand.
A constricted vapor hose will also cause fuel deficiency because the engine induction vacuum (that is supposed to unseat the regulator secondary valve) will be greatly reduced inside the regulator secondary chamber.
For this engine, the vapor fittings at the mixer and at the regulator should be 5/8" size.
  • Posted 22 Nov 2012 03:57
  • Reply by L1ftmech
  • Tennessee, United States
It's got to be running out of gas due to lock off, hoses, or tank and coupler. Do that test again that you take the hose off and energize the lock lock and let it stay on for 3 seconds, outside and carefully.
  • Posted 22 Nov 2012 03:50
  • Modified 22 Nov 2012 08:48 by poster
  • Reply by mrfixit
  • New York, United States
Model J regulator, CA100 mixer.

The bulkhead fitting has less than 25 hrs on it and the filter appears to be as new.
Perhaps it's impossible to visually tell if the felt filter is clogged?

Liquid fuel out of the end of the hose fitting just before the regulator (where it goes INTO the fuel solenoid). Also liquid fuel out of the solenoid valve when energized. And for several seconds, not just a split second. I wanted to be certain there was plenty of free flowing fuel available up to the regulator.
It blasts out the end of the hose.

No VFF-30....there is a vacuum switch in the circuit with the fuel solenoid.....which is bypassed for testing.

I am positive it goes lean now because I had my hand almost completely over the air intake and it ran fairly well till it got so lean it died. It seems to run 30 seconds or so the lean out and stall. It actually sat there at high idle and then quit more than once.

Also tested with carb cleaner and it runs OK and steady on that, as long as I'm spraying it in the carb in a steady stream.


I can check the ignition also, but it really seems like fuel delivery problems.

Any way to test the regulator??

I will try a different tank too!

  • Posted 22 Nov 2012 03:40
  • Modified 22 Nov 2012 03:50 by poster
  • Reply by dkmc
  • New York, United States
May I suggest that you keep in mind that we are trying to help you- being short & demeaning with the hand that feeds you (hats off to Swoop 223 for taking his time & talents in trying to help you) isn't the best way to get the help you require.

The proper Impco fuel system for your application would be the VFF-30 vacuum lock off, Model J or Cobra regulator/vaporizer & CA100 carburator/mixer.

Perhaps if you explained yourself more clearly our answers would be more on target. Your symptoms can be caused by a few different issues, proper diagnoses & comunication can get us to resolve this, if we work together.

Have you concidered the ignition system- have you checked for spark when the unit is begining to die? As mentioned- have you checked for a clogged fuel filter at the bulkhead fitting? Have you checked the connector at the fuel tank? And lastly, have you tried using different propane tanks? These should be the basic tests being done before diving into the fuel system components.

And for the record, I personally have never seen a pnuematic governor exhibit the symptoms you have.
  • Posted 22 Nov 2012 02:50
  • Modified 22 Nov 2012 02:55 by poster
  • Reply by bbforks
  • Pennsylvania, United States
bbforks (at) Hotmail (dot) com
Customers love technology- until they have to pay to fix it!
You said, "I tested the fuel solenoid WITH THE TANK VALVE CRACKED OPEN and the fuel hose disconnected completely from the regulator.....liquid fuel came out...... "

Are you meaning that you disconnected the fuel vapor hose that leads from regulator to the mixer? and liquid fuel pours out of the regulator at that hose nipple on the regulator?
Tell us WHICH Impco regulator and mixer you installed.
  • Posted 22 Nov 2012 01:56
  • Reply by L1ftmech
  • Tennessee, United States
The regulator and carb on there now is NEW
There is no fuel leaking in the carb now......read my post carefully.

I tested the fuel solenoid WITH THE TANK VALVE CRACKED OPEN and the fuel hose disconnected completely from the regulator.....liquid fuel came out......

  • Posted 22 Nov 2012 00:17
  • Reply by dkmc
  • New York, United States
if you are hearing a hissing at the mixer when you turn the key on even while the engine is not running this should not be happening. the diaphragm in the mixer is what regulates the flow of vapor into the engine but only when it is running, it opens and closes using the engine vacum from the engine via a vacum hose coming from the intake manifold and should only open the mixer under vacum while the engine is running. If you are getting a hissing sound just by turning on the system i would make sure the diaphragm is not damaged. Pull the cover off the mixer and remove that diaphragm and check it for any holes, cracks and pay close attention to the center button on the diaphragm itself and also inside the mixer where it seats, this is what actually seals the vapor. A dirty or bad seat on the diaphragm button can allow vapor to pass when it is actually supposed to be closed and can make the engine run badly or not at all.
  • Posted 21 Nov 2012 21:55
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
Hmmm. Maybe try this test just to prove it is a fuel problem. Rev it up and get it to stumble and ready to stall, then spray a shot of WD-40 in the carb and see if it wants to take back off and rev. It sure acts like it is running out of gas. How about the fuel tank coupler? If that had a problem it would still give you a shot of gas out of the disconnected hose because the hose was full but maybe its not coming out of the tank properly.
  • Posted 21 Nov 2012 21:02
  • Modified 21 Nov 2012 21:30 by poster
  • Reply by mrfixit
  • New York, United States
I had the hose to the PCV valve plugged
And I took the high pressure fuel line off the regulator and
momentarily bumped the key......plenty of liquid propane came out of the hose.

  • Posted 21 Nov 2012 12:27
  • Reply by dkmc
  • New York, United States
There is no diaphragm that can cause a vacuum leak. Bad gaskets could. There is a spring in there, that if it breaks, the throttle plate will close too easily and won't rev up. It sounds like maybe the fuel filter, located between the tank and the lock off solenoid, could be plugged enough to be restricting the fuel flow. The flow may be good enough for idle but when throttled up the flow may not be good enough and the pressure starts to drop in the hose downstream of the filter and after 20-30-60 seconds it goes lean and stalls. Also, I would check the PVC valve.
  • Posted 21 Nov 2012 11:16
  • Reply by mrfixit
  • New York, United States

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