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 16 - 30 of 55 results.
Rest assured that if the parts say Impco on them they are genuine Impco. Algas was bought out by Impco many years ago along with Beam.
  • Posted 25 Nov 2012 03:00
  • Reply by Partsguy5
  • California, United States
Well, I don't really know.......

The parts were ordered from an IMPCO distributor whom I was referred to after I called the IMPCO headquarters, and the parts all say IMPCO on them, cast into the aluminum.
The part numbers all seem to match IMPCO part numbers in the IMPCO catalog.......

But maybe they really are not IMPCO after all....

  • Posted 25 Nov 2012 02:37
  • Reply by dkmc
  • New York, United States
Are you sure you are dealing with an Impco and not an Algas fuel system. It seem so.
  • Posted 25 Nov 2012 00:34
  • Modified 25 Nov 2012 00:36 by poster
  • Reply by MEngr
  • Missouri, United States
Well, knowing the regulator is 25 years old makes it suspect anyway.
I just bought a kit today for a Model J reg and a VFF 30 lockoff from our local Toyota dealer in the Star Lift Parts line of parts.
That is Toyota's alternative parts line but the parts in the bag were genuine Impco brand.
The Toyota part number for the J model rebuild kit is 00591-51142-81. Comes with its own instruction booklet and the cost was $17.31 USD.
  • Posted 24 Nov 2012 15:08
  • Reply by L1ftmech
  • Tennessee, United States
I'm not sure how the WP rating from the old BEAM equipment and the new IMPCO equipment are related?

The IMPCO reg and carb are designed to work together.

The BEAM system is 250lbs WP 0.19 PSI water column.
The IMPCO system is 312lbs WP and 2 inches WC

I took off the cover on the primer button side.
The diaphragm looked -as new- I looked carefully and closely
and saw no holes or rips or cracks.

Put it back on and tried to start the engine.
I noticed propane smell and looked everything over carefully.
Gas is escaping from the vent screen.
A slow steady silent flow of gas.
The primer button seems to have a lot of resistance when pushed. It was that way before.

So apparently sitting around for 25 years never being used has still had ill effects on the rubber products in the unit.
This was never installed on anything, it is as new.

I am ordering a rebuild kit right now.
  • Posted 24 Nov 2012 04:29
  • Modified 24 Nov 2012 04:32 by poster
  • Reply by dkmc
  • New York, United States
by closing off the air intake hose your equalizing the air/fuel mixture which tells me that it is not getting enough fuel if that makes it run better.
by pressing the primer button your adding fuel to the mix so all this tells me the regulator is not delivering enough fuel.

take a look on the origional regulator and see that the W.P rating is on it, then look on the new one you installed and see what it is.
The W.P rating is the working pressure rating, some are different than others. But all in all since this regulator is so old i'd be willing to bet it is either the wrong pressure rating OR what others have said, it may have a bad diaphram or something. Also make sure the fuel filter isnt clogged up, we'll assume it is not since you already removed the fuel inlet line and got good squirt of raw gas from the line when you cracked the valve on the tank.
  • Posted 23 Nov 2012 23:43
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!
DMV, you aught to by your self a repair kit for this unit, it's a straight forward job to install the diaphragms and any springs you get with the kit, this unit did not come of another truck 25years ago did it. The thought being this will come in useful one day, I'm sure we have all done it at sometime or another.if that's the case then you may find that heavy ends have solidified in the honeycomb tracking as I call it, it's easy enough to clean out.

Regards Titus
  • Posted 23 Nov 2012 20:21
  • Reply by Titus
  • North Yorkshire, United Kingdom
What doo I look for??
How will I know a defective diaphragm?
Is it obvious?
  • Posted 23 Nov 2012 15:14
  • Reply by dkmc
  • New York, United States
Yes, a pin hole or a small tear could certainly explain the drop off after an initial good rev up.
Going to be interesting to hear about that diaphragm inspection.
  • Posted 23 Nov 2012 14:59
  • Reply by L1ftmech
  • Tennessee, United States
Take the cover off the side with the push button and it's right there.
  • Posted 23 Nov 2012 12:18
  • Reply by mrfixit
  • New York, United States
Well, the carb is new.....bought last week.

The reg. is unused, but 25 years old.

So I guess it would be the Reg.
  • Posted 23 Nov 2012 11:22
  • Reply by dkmc
  • New York, United States
Now my guess is the diaphram in the regulautor or carburetor leaks.
  • Posted 23 Nov 2012 10:23
  • Reply by mrfixit
  • New York, United States
Mr fixit is definately on the right track here it sounds more and more like a blocked fuel filter, if there is a fuel stop solenoid at the base of the carb which is subject to vacuum activation then if there is a gasket or manifold leak then this may should down as the vacuum falls thus stalling the engine. It may not have a fuel stop solenoid if not set the power mixture valve to the half way mark,
Screw the idle mixture screw up fully and then back of four turns and see if the engine will idle as this should give the engine a reasonably rich mixture if it still stalls out you will have to look for an air leak or a blocked filter.

Regards Titus
  • Posted 23 Nov 2012 09:30
  • Reply by Titus
  • North Yorkshire, United Kingdom
Well......I spent an hour with it in a more relaxed and paicient
state of mind instead of trying to find a "pit stop" solution.

As a test I managed to install a piece of 5/8 ID hose in place of the 1/2" OD copper tube between the reg and "carb".

No difference in symtoms.....still goes lean after 20-30 seconds.

Here's the progress part:
I do now KNOW for certain it is going lean as I was able to help it by choking down the air inlet -carefully- and more precisely with my hand and actually keep it running.

The possible culprit:

In this process I have also found I can "play" with the primer button on the Model J and advert stalling altogether!
Matter of fact, after a short learning curve (lol) I found if I play the primer button in sync with the throttle, I can go from idle to wide open with no lean out.

And it seems if I just hold the primer button in with little force from my finger, the whole program seems to improve over the entire no load speed range.

Whe I leave the button alone, again, it will idle for 20-or-so seconds and then 'go lean'.

This Model J regulator has sat in a drawer for aprox. 25 years and was never used.
Is it possible time and age has damaged the internal rubber parts? There were no plugs in the ports, they did look clean, but I suppose it may have dust in it.......

I guess the next step is to do the pressure test and probably disassemble it for inspection.

Oh.......also had a timming light hooked up to the coil wire all the while, and it did seemed to be a steady output with no misses or shut offs.
  • Posted 23 Nov 2012 06:25
  • Modified 23 Nov 2012 06:42 by poster
  • Reply by dkmc
  • New York, United States
sorry dk,
musta overlooked that part
was basing my response on your origional post only
  • Posted 22 Nov 2012 20:10
  • Modified 22 Nov 2012 20:13 by poster
  • Reply by swoop223
  • North Carolina, United States
You've been swooped!

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