Propane trick

[RRich]

With all the BBS changes, I thought it would be a good idea to re-post this:

Often engine ills can be traced back to the fuel mixture,
too much or not enough fuel.
Measurements can be done with expensive instrumentation to
determine whether the mixture is right for that engine, but
there's an easy and inexpensive way as well.
Propane burns nearly the same as gasoline, and can be used
to temporarily richen the mixture.

Use an inexpensive propane torch, the cheap ones are the
best. It takes a little modification to the torch before
it will work effectively. Remove the tiny orfice, the tiny
hole that restricts the amount of propane that can be released.
Sometimes the orfice is removable, sometimes it needs to be
drilled out. Use the smallest drill bit you have to enlarge
the hair-like hole.

It will not do the job if you do not drill or remove the orfice,
it will not give enough propane.

Also remove the torch head, either by unscrewing it or cutting
it off. What you end up with is just the valve.
Connect the valve to a small propane bottle, like the torch
would use.
To make sure you have correctly removed the orfice, hold the
bottle with the valve down and open the valve - you should
get lots of propane, some liquid, mostly gas.
DO NOT DO THIS NEAR A FLAME - or you'll be surprised.

Slip a long vacuum hose over the pipe, long enough to reach
the air intake stream, like the carb's snout, from the
driver's seat.
Now you have a tool that will help you diagnose lots of
problems.

Operation - hold the bottle with the valve on top, you get
propane gas for low RPM tests. Hold it upside down you get
liquid propane for high RPM or under load tests.

BE CAREFUL - PROPANE IGNITES VERY EASILY -- Do not spray it
on the distributor or on bad ignition wires, or on any sparking
device, like an alternator.

Vacuum leaks - Valve at the top for gas - simply spray a
little propane around the suspected areas, like carb base
gaskets, vacuum tees, intake gaskets, injector seals,
brake booster, hoses, etc. When you hit the leak with the
propane the RPM will change. If someone has already tried
to adjust the carb with the leak present, the carb may well
be adjusted too rich, nullifying the propane. In that case,
simply lean the mixture down with the idle screws till it runs
rough, then use the propane. Make it lean on purpose and
the system becomes very sensitive. Even tiny leaks can be
found in this manner.
Unlike liquids, like carb cleaner, gasoline, ether etc.,
propane will not wash dirt into the leak's hole, temporarily
plugging it. And, unlike liquids, in case it does happen to
ignite, it flashes, burns fast, scares hell out of you, but
once it flashes the flame goes out. A liquid makes puddles
that continue to burn causing extensive damage.

Yes, it will scare hell out of you - you'll leave some hair
on the hood latch too.

Remember, propane is heavy, so it will collect in low places.
It also tends to blow around, and being invisible you can't
see where it's really going. Use it sparingly. --
(No, the heater hose doesn't have a vacuum leak, the propane's
blowing back into the carb.)

Idle Mixture - Valve at the top for gas - if the mixture is
set properly, adding just a touch of propane will speed the
engine up ever so slightly. Adding more propane will cause
the speed to drop.
Experiment with that - notice just a little propane speeds
it up, more slows it down. That's because the ideal setting
is just slightly lean. If it was set too lean. the R's will
really rise - the engine "likes it." If it was too rich,
adding propane will make the R's only drop. The curve is a
bell shaped curve, with a slightly flat top. Get a good
"feel" for that.

Cruise Speed under load - Valve at the bottom for liquid.
Tape or attach the hose to the air intake - right in the
airstream. Run the long hose and valve to the driver's seat.
Go for a ride. The same principle applies at speed under
light load. Adding propane should just barely increase the
speed if it is already getting the right mixture of gasoline.
Adding more should slow it down - too rich.
If the engine "really likes it" you were too lean.
This is a great way to determine whether or not you need to
change jets, and which way, richer or leaner. Who needs
$50,000 worth of equipment when you can do it for $5?

Diagnosis - often the question is whether or not a problem
is fuel or ignition related. Simply duplicate the condition
where the poor running or misfire occurs, then add propane.
Obviously if adding the fuel makes the problem "go away" it
was a fuel problem.

Stumble On Acceleration - a popular problem. Bad accelerator
pump? Snap the throttle to make it stumble, but while you
snap the throttle, snap the propane valve open at the same
time. It takes a little practice, but if the stumble dissapears
-- guess what? Propane won't help wrong timing advance.

Closed Loop Systems - Whenever you add propane the engine
will react as above, but the computer will see the RPM change
and compensate in 2 ways. At idle it will re-adjust the
IAC till the RPM returns to the preset idle speed. At higher
speeds the O2 sensor detects the added fuel and cuts back on
the gasoline. The end result is it will momentarily have a
reaction, then return to what it was before. Then, when
you turn off the propane it will do exactly the opposite.
For example on an engine with a vacuum leak: The engine will
be running rough but at normal speed. When you "hit the hole"
the R's will increase a moment, then drop down again.
But - you'll notice the engine is running smoother now.
Then when you remove the propane, the R's drop suddenly as
it becomes way too lean for an instant, then it returns to
normal again.
The reaction, lean/rich, is the same as with open loop, but
only for a quick instant.

"False Air" on MAF Vehicles - Spray a little on the ducting
between the MAF sensor and the throttle body. The ducting
should be sealed, no leaks, a common problem.

Priming an Engine - shoot a good shot of propane into the
aircleaner, start it up. If it backfires it won't sit there
and burn like it will when you pour gas down the throat - and
you don't have to remove the aircleaner.

Most vehicles can run completely on the propane from your
valve. If an engine is hard to start, try adding a shot of
propane to see if it helps. Remember the amount of fuel is
determined by the valve, the amount of air is determined by
the throttle opening. I've even driven my van a few blocks
on the propane when I ran out of gas in the rain and didn't
want to walk.

You'll find this tool becomes one of your handiest tools in
your toolbox.

Remember - propane ignites easily - observe all the safety
rules, be careful and it can be your friend.

---- BE CAREFUL! ----
_________________

[WalterX]

RRich,

The first line in this trick should always read....."Find a Fire Extinguisher."

Always a great tool though!

[RRich]

You really shouldn't need a fire extinguisher. It's a gas vapor - if for some reason it does ignite - it flashes fast, then goes out. Using ether, carb cleaner or other liquids puddle on everything - when they ignite they burn longer, doing more damage.

He He -- One time I was demonstrating how to use it - we were looking toward the scope at the reactions. The hose flipped around and went in the GM cap - the little door was missing. It filled the cap with propane - POW - the cap blew off!
No fire, but my face was red - not from the explosion, but from embarrassment - DUH!

Of course - you use it UNLIT!

[Jeepster Jim]

Originally Posted by RRich

You really shouldn't need a fire extinguisher. It's a gas vapor - if for some reason it does ignite - it flashes fast, then goes out. Using ether, carb cleaner or other liquids puddle on everything - when they ignite they burn longer, doing more damage.

He He -- One time I was demonstrating how to use it - we were looking toward the scope at the reactions. The hose flipped around and went in the GM cap - the little door was missing. It filled the cap with propane - POW - the cap blew off!
No fire, but my face was red - not from the explosion, but from embarrassment - DUH!

Of course - you use it UNLIT!

Rummors have it that RRich torched himself and ended up with a "Don King" hair do LOL

[GoldToyBox]

The damnist things happen at the damnist times!
Great post

Bumping BTT