Propane generator setup

 I recently acquired a DeVilbiss GT5000 w/Tecumseh 10hp HM100 that has
already been converted to dual fuel.  It has an Impco VFF30-2-4 feeding
a Beam T50G feeding a venturi adapter (no name).

The problem I am having is getting it to start and stay running from
propane.  I can warm it up on gasoline and then switch to propane and
it runs fine, but cannot get it to start cold and stay running on
propane, even on a mild 50-60 degree day.  It will fire and perhaps run
for 10 seconds, then die.

The lockoff is working and the regulator appears to be working
properly.  I can see vapor exiting the hose (lazily, but I assume the
engine will draw what it needs under vacuum) if I open the lockoff with
vacuum hand pump.  Have also tried both vapor feed and liquid feed to
the VFF30.

I have tried adjusting both the adjustment screw on the regulator and
the large needle valve going into the venturi (load block?), with no
luck.  Also tried keeping the lockoff open with hand pump to eliminate
lack of vacuum as the cause.

Any help to get this setup would be greatly appreciated.

  The zero pressure regulator (the thing with the big diaphragm that
connects to the "carburetor".) is mis-adjusted or else something is
wrong with the carb so that not enough vacuum signal is being
developed.

The zero pressure regulator is just that.  It should be closed at zero
pressure but open at the slightest negative pressure.  It meters
propane according to the vacuum developed in the carb's venturi.

Another possible problem is not enough signal being developed at
cranking.  Make sure the choke shuts completely.  If the regulator is
properly adjusted and the choke is shutting as it should then it may
be necessary to plug and redrill the choke bleed hole to a smaller
size.

Make a water manometer and Tee it into the propane feed line to the
carb.  You should see significant depression - at least a half inch of
water - during cranking.  If not then there is your problem.  A 10 HP
engine with the choke fully closed should develop a large signal -
several inches of water.

Some versions of the Impco zero pressure regulator have a primer
button.  This is a little spring-loaded button on the regulator body
that lifts the regulator needle and lets some propane flow to the carb
even with no vacuum signal.  If yours has that, be sure to use it.

The guys who used to maintain the floors at my restaurant used a
buffer with a 16hp honda engine equipped with a primer zero pressure
regulator.  It required considerable cranking even with the button
depressed. Both of their buffers acted this way but they're the only
instance I've seen of this behavior.  Just mentioning it in case yours
ends up with that characteristic.

Oh, and since this is a dual fuel unit, make sure that the choke
you're using is upstream (toward the air cleaner) of the propane carb.

On 9 Nov 2006 19:32:05 -0800, kent.mccarthy@gmail.com wrote:


John De Armond
See my website for my current email address
http://www.neon-john.com
Cleveland, Occupied TN
Don't let your schooling interfere with your education-Mark Twain

 
Neon John wrote:


Thanks, John, it was the choke.  I didn't realize that the gasoline
carb's choke should be closed for it to develop enough vacuum to hold
the lockoff open.  That's why it would run for 10-20 seconds, but when
all the primed lp gas was drawn from the regulator it would die.  Once
the engine warms up, the choke can be opened - the rings must seal
better and produce more vacuum, which makes sense.

 kent.mccarthy@gmail.com wrote:

You don't say whether this is a new or second hand unit.

If S/H you may need to clean the gas converter. A waxy build up inside
the converter will cause moving parts to stick, once warm the waxy
substance is soft enough for moving parts to move.

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