View Full Version : Propane mixer question??

07-13-2008, 11:03 PM
Hey guys.. I got spark and the timing "close" on my lil' forklift tonight. Just trying to get it to fire and run for a short burp so I can see if the engine is worth fooling with any further. I don't want to put a bunch of time and money into a dead pig.
I loosened off the propane mixer took out one bolt and twisted it enough to pour a slug of gas down the manifold. Seems like it isn't even sucking the gas into the cylinders. I poured gas into the cylinders through the sparkplug holes but the thing is acting weird. I'm wondering... propane mixers... do they need the pressure of the gas to open them?
Seems like the thing isn't getting any air. It's firing but sounds very weird.
Any ideas?

doctor demo
07-13-2008, 11:36 PM
Russ, Have You done a compression and leak-down test ?
It seems that You might have stuck valves/rings.

07-14-2008, 12:16 AM

I recommend you remove the intake/exhaust manifold and clean out
all the carbon buildup within it.


07-14-2008, 12:32 AM

I recommend you remove the intake/exhaust manifold and clean out
all the carbon buildup within it.

Patch.. it was on LPG.. there is no carbon that i can see in any of the valves etc..
Steve... it looks like all the valves are working fine. Ya.. I better take a compression test in the morning. I'm now thinkin I may just twist the mixer a bit to act as a butterfly..it'll get air then.
I was told by the last owner that used this that it did run when they parked it. It belonged to Pepsi. They had to upgrade it due to Compensation infractions... but that could be BS also....I will be the only one to know for sure :D

07-14-2008, 01:31 AM
Your plugs could also be totally shot.

Propane generally is so easy on engine and ignition components that nothing ever gets done to them service wise.

I have had several that ran like crap until I cleaned and gapped the plugs.Last one was our old Datsun at work,it acted like poor compression,but turned out to be points.The little bearing pad that rides the dist cam was worn smooth off,points wern't even opening:D

I used to take the mixer off the intake and stick the snout of a propane torch over it.Open the valve and spin then over,usually they would pop and half arsed run,if they did that it wouldn't take much to make them run.

07-14-2008, 03:16 AM
Distributor contact point gap 0.022 Inch (0.56mm)
Distributor cam dwell angle 25 - 34 Degrees
Engine compression (At cranking speed) 145 within 10 PSI (10.2 within 0.7 kg/square cm)
Idle mixture adjustment LPG (Impco) 2 to 4 turns out from full in position.
Ignition timing 5* BTDC
Spark plug make Hyster Part No. 138366
Spark plug size 18mm
Spark plug gap 0.025 Inch (0.64mm)
Valve tappet clearances Intake 0.012 Inch (0.31mm) Hot or Cold
Valve tappet clearance Exhaust 0.020 Inch (0.51mm) Hot or Cold

07-14-2008, 08:13 AM

I'm not sure what you are talking about

the mixer is the doughnut shaped thing that puts the LPG into the manifold

the vapouriser is the gadget that turns liquid LPG into a gas

the vapouriser ...has a tick over circuit operated by selonoids....

it will pump gas for several seconds ...when you first turn on the ignition ...
if there is no coil pulsed signal after those several seconds .....(the engine hasn't started ) then it will close the solenoid and stop the LPG

When the engine does start...once the engine is revved a bit ...it goes onto main gas ...this is achieved by the vacuum pull of the engine ...acting on the diaphragm in the vapouriser ...

all the best.markj