Propane as an alternative fuel – 1994 Toyota Pickup 2wd

I was looking for an older truck to move heavy things around like a motor block, transmission, or anything bigger than my car trunk.  I’m not a picky person, and was aiming for an 80’s Ford F150 or Ranger.  I ran across a truck that caught my attention since I like to experiment.  A 1994 Toyota 2wd pickup that was converted to propane and turbocharged!

This particular one is rather unique in that it’s been a test-bed demo truck most of it’s life.  For the last 5-8 years she’s been living the used-truck life in the hands of 2-3 people, however.  The conversion to propane is the awesome part – All of the vacuum tubes & emissions stuff in the engine bay is gone, with the EFI system capped & fuel injectors unplugged.  A 27-gallon ASME horizontal propane tank is bolted into the bed of the truck.

A propane hose is mounted through the floor of the truck bed, running through the frame into the engine bay running through the firewall where it connects to a propane filter, propane regulator, propane vaporizer, & propane mixer/carburetor.  The mixer/carburetor feeds directly into a Garrett T3 turbocharger (mounted on the engine exhaust manifold), with the EFI system intake tube feeding directly from the turbocharger.  Below is a picture of my engine bay.

The ignition coil & module on my setup (as seen in this photo below the mixer & vaporizer) is custom, with a higher amperage pass-through to detonate the propane with a solid spark.  I’m running NEW stock NGK plugs, distributor cap/rotor, & NGK ignition wires.

Since there is a turbocharger on the system, an HKS turbo timer is installed, and vacuum sensor to be able to detect boost/air fuel ratio (AFR)/PSI/etc.  It helps alot when tuning the mixer after installation!  Another thing to note is on my setup the turbocharger has a direct oil feed from the oil sensor on the engine block to the turbocharger bearing and back around through a filter dedicated to the turbocharger, and back around into the block.

For those who don’t feel like worrying about installing vacuum sensors, etc, you can tune the mixer just as I did:  the air/fuel screw 4 1/4 turns out and the WOT knob just a hair under fully rich.

The plus side of propane in Arizona is the ability to get an Alternative Fuel plate which allows driving in the HOV lane!  Propane also has a much higher octane, which allows a much higher compression ratio (14:1 or higher).  It requires a hotter spark to ignite, but burns clean with far less CO2 exhaust.  Propane enters the engine as a vapor (non-liquid) gas, with none passing the piston rings into the oil.  Propane also is VERY stable, and will not go bad just sitting in the tank, unlike gasoline which rots.  The negative is that propane gets a lower MPG by 10% or so, but usually is negated to the same MPG with a turbocharger.

The 1994 Toyota pickup is a reliable vehicle, but is not smooth riding.  Due to it’s light body, a bump is really felt but it sustains nicely.  Driving to work (30 miles one way, freeway) is rather nice, however.  Since it is turbocharged, the life really shows above 55 MPH and with a 5-speed manual transmission (5th gear is overdrive) the RPMs aren’t very high at about 3300 RPM at 80 MPH.

I have a few fixes to do, with the lower engine needing to have seals replaced to stop oil leaks along with maintenance changes of coolant hoses & water pump before the summer comes.