There should not be,  there are lockouts on the propane delivery system but
not ignition.
trace your loss of spsrk bacwards through the distributor and then to the
coil.  The coil should be wired to the ignition wire from tthe ignition
switch ( I assume it is a points type ignition by your post) small stud with
nut and the other small stud with nut to the points in the dist and the
other side of the points to ground. Obviously the centre HT lead goes to the
dist..
With engine stopped disconnect the HT (coil to dist) lead from the
distributor take off the dist cap  and turn the engine until the points are
closed. Secure the dist end of the HT close to a ground away from the
carburettor, and turn on the ignition, now with a screw driver gently push
on the points arm, cam side, to open the points and a small spark should
jump the points and at the same time a large spark should jump the HT to
ground.  If this does not happen, check for 12 volts across open points
(should be there) , then turn off igntion and check again for fro 0 voltage,
then check your condenser for a short   should be no conductivity between
lead and ground.  If all this is here and still no spark chech with a new HT
lead and make sure it is plugged ALL the way in.  If you got a spark off the
coil you should be able to trace things down the line from there

hey all,

I'm posting for a friend, but witnessed the events leading to this post.

We removed the propane system from a 1971 Imperial w/440.And replaced all of
the fuel components to go back on pump gas, including a new carb, fuel pump,
lines and sending unit.

We are under the impression we removed all components properly, but for some
reason now we get no spark. The points,rotor,cap,wires,and plugs were all
replaced and the coil seems fine.

My question is : Is there an electrical interruption installed in a propane
system that will not allow spark unless some sort of condition is met ?

Also : If someone has a schematic for the ignition on a 440 in it's original
state that would help too as we are not exactly sure the coil was hooked up
properly.

Any info or thoughts are appreciated, or perhaps a website that may have
that info.

Thanking in advance ...