INNOVATECH PRODUCTS & EQUIPMENT CO., INC.
26
IMPCO FUEL SYSTEM ADJUSTMENT INSTRUCTIONS
1. BE SURE THAT WATER HOSES, FUEL HOSES AND WIRES ARE PROPERLY FASTENED IN PLACE. THEY SHOULD BE CLEAR
OF EXHAUST SYSTEM AND SHARP OBJECTS.
2. BEGIN TO PRESSURIZE THE FUEL SYSTEM BY OPENING THE FUEL CYLINDER HAND VALVE SLOWLY AND CONTINUE AS
FOLLOWS:
A. SYSTEMS WITH VACUUM OPERATED SHUTOFF VALVES SUCH AS THE IMPCO VFF30 MUST HAVE VACUUM APPLIED
TO THE VALVE TO ALLOW FUEL TO PASS THROUGH TO THE VAPORIZER-REGULATOR. THIS CAN BE DONE BY
OPERATING THE ENGINE CRANKING MOTOR.
B. SYSTEMS WITH ELECTRICALLY OPERATED SHUTOFF VALVES MUST HAVE CURRENT TO THE VALVE BEFORE IT
OPENS AND ALLOWS FUEL TO PASS THROUGH. A VACUUM SWITCH OR OIL PRESSURE SWITCH MUST BE USED AS
AN ADDITIONAL SAFETY AND SIRED IN SERIES WITH THE ELECTRIC SOLENOID. ACTUATING EITHER OF THESE
CAN BE DONE WITH THE CRANKING MOTOR. IT MAY TAKE MORE CRANKING TO ACTUATE THE OIL PRESSURE
SWITCH.
3. CHECK ALL OF THE FUEL CONNECTIONS FOR LEAKS WITH AN APPROVED LEAK CHECK SOLUTION THAT CAN BE
ORDERED FROM YOUR LPG PARTS SUPPLIER.
4. THE FUEL CYLINDER MUST BE LOCATED WITHIN THE OUTER LIMITS OF THE MACHINE.
BEFORE YOU MAKE ANY FUEL ADJUSTMENTS:
1. THE AIR CLEANER SHOULD BE INSTALLED.
2. IGNITION TIMING MUST BE CHECKED AND ADJUSTED PER THE ENGINE MANUFACTURER’S SPECIFICATIONS. PROPANE
BURNS SLOWER THAN GASOLINE. RETARDED TIMING WILL REDUCE HORSEPOWER AND INCREASE EXHAUST
EMISSIONS. MOST MANUFACTURERS RECOMMEND ADVANCING THE TIMING 3 TO 5 DEGREES. THIS WILL INCREASE
LOWER END TORQUE HORSEPOWER; HOWEVER YOU MAY EXPERIENCE A LOSS OF POWER UNDER EXTREME HEAVY
LOAD CONDITIONS. WHEN MACHINES ARE WORKED VERY HARD, BE CAREFUL NOT TO ADVANCE THE TIMING
BEYOND THE MANUFACTURER’S RECOMMENDATION. THIS WOULD CAUSE UNNECESSARY STRESS ON THE ENGINE.
3.CONVERTING ENGINES TO BURN PROPANE MAY CAUSE THE GOVERNED ENGINE SPEED TO CHANGE. TO MAINTAIN THE
TRUCK’S “NO LOAD” AND “LIGHT LOAD” DRIVABILITY, IT MAY BE NECESSARY TO RESET THE GOVERNOR TO FACTORY
SPECIFICATIONS. THE ENGINE MUST BE AT ITS NORMAL OPERATING TEMPERATURE PRIOR TO MAKING ANY
ADJUSTMENTS.
4. THE ENGINE AND TRANSMISSION SHOULD BE AT OPERATING TEMPERATURES.
POWER ADJUSTMENT:
FULL POWER MIXTURES ARE CONTROLLED BY THE MIXTURE ADJUSTMENT AT THE FUEL INLET OF THE MIXER. THE FUEL
MIXER CASTING IS MARKED WITH AN “R&L” INDICATIONS THE FULL, RICH AND LEAN POSITIONS OF THE VALVE. THIS
ADJUSTMENT WILL CONTROL THE FULL LOAD FUEL MIXTURE AND MUST BE MADE WITH THE ENGINE UNDER FULL OR
WORKING LOAD.
IDLE ADJUSTMENT:
TURNING THE SCREW “IN” WILL MAKE THE FUEL MIXTURE RICHER AND TURNING IT “OUT” WILL MAKE IT LEAN. THIS
ADJUSTMENT MUST BE MADE AT THE MANUFACTURER’S RECOMMENDED IDLE RPM.
WE STERNLY RECOMMEND THAT YOU USE A CARBON MONOXIDE FUEL ANALYZER TO ADJUST THE FUEL MIXTURE.
READINGS USING CARBON MONOXIDE ANALYZER:
POWER MIXTURE - .1 TO .2 PERCENT
IDLE MIXTURE - .5 TO .75 PERCENT
READINGS USING AIR FUEL RATIO ANALYZER:
POWER SETTING - 15.5 – 16 TO 1
IDLE SETTING - 14.5 TO 1
NOTE: WHEN EXHAUST ANALYZERS ARE NOT AVAILABLE, A TACHOMETER MAY BE USED.
MAKE FUEL ADJUSTMENTS TO OBTAIN MAXIMUM RPM READING, THEN LEAN FUEL MIXTURE TO LOWER READINGS TO 10 – 20 RPM.
