Terrible fuel economy on autogas / propane

[Therrol]

Hey guys, i've got a 1986 Dodge B250 I just purchased. It's stock propane, and i've been forced to into a bit of a reality check in the few days i've owned it.

It's got two tanks, a stock one and an auxillary tank. For some reason the main tank doesn't work, it just dies a few moments after I switch. The auxillary tank is pretty small. I'm not sure of the exact volume, but it costs about $40 CAD to fill up at 88c per liter. So i'm guessing the tank is 40 or 50 liters (hard to tell how empty it is with the fuel gauge. This only got me 80KM in the city, and 120KM on the highway. This works out to an insane 50L / 100KM or less than 5 MPG. The previous owner told me that he would get 600KM with both tanks. Assuming the second tank is about twice as big as the first, that's about 10MPG which is what I was expecting. Anyone have experience with fuel economy on a propane vehicle?

I've got a V8 318.

 

[WriterMs]

Are propane fueled more common in Canada? Must be. Since no one has replied, I thought I'd type something here to send the thread back up through the "Today's Posts" to see if there is someone who can advise you but did not see the question the first time around.

 

[wagoneer]

Can you switch to natural gas ? I have no experience .

 

[becida]

Propane has less energy (in a given amount) than gasoline, so you'd get less miles/gal than gasoline. No idea what the problem is with the tank switch, I'd wonder if it's actually working? 80 km between refueling stops would be hard to live with....

 

[highdesertranger]

A propane powered vehicle can be converted to gasoline fairly easily. you could also make it a dual fuel vehicle. like Rob said propane has less energy per unit than gas so you get less MPG. highdesertranger

 

[Optimistic Paranoid]

Can you switch to natural gas ? I have no experience .

No.  Propane tanks hold liquid and operate at about 400 psi.  Natural Gas is compressed gas and operates at around 3000 psi.

 

[Optimistic Paranoid]

About the only helpful suggestion I can make is to consider the possibility that you have a fuel leak, one that only leaks when the vehicle is running.  I had this happen once on a gasoline powered car.  There was a pinhole leak in a rubber hose, but it was at a high point in the fuel line, so it only leaked when the fuel pump was pushing fuel through the line.  Boy, did THAT play hell with my mpg!

Try letting the vehicle idol, on level ground, over a clean area, and check for leaks underneath.

 

[Therrol]

Hey guys, thanks for all the tips. I did end up figuring out. Turns out, it all boils down to driving habits. I think I was a little over excited about the concept of having a V8 318 so perhaps I was too heavy with my foot. The highways here are 120 km/h. I found that driving 80 to 90 drastically improved my fuel economy. I was getting roughly 10mpg on the same drive back. Considering the cost of propane, that means that the operational costs of the vehicle average $22 / 100km. Compare that with $10 / 100km of a 4 cylinder ford focus, and i'm happy with the results.

I did get the second tank working. It's much larger than the first. I get about 400km on that tank, and the second one is around 130km. It was the switch after all. The part was inexpensive and easy to install. For anyone else trying the same thing, all you have to do is close the isolation valves on the tanks and idle the vehicle until it dies. Then carefully remove the fuel hoses, bold the new one in place, rewire it, and connect the fuel lines again. I then let the van sit for a while so the propane smell could dissipate, then slowly opened the isolation valves. You can drip a bit of soapy water onto the fittings. if you see bubbles, there is a leak.

Also remember that propane fittings are reverse threaded. You don't want to accidentally tighten them to the point of stripping the threads when you're trying to remove the hoses.

 

[Willy]

I'd love to get 10 mpg with my propane rig. I think 6-7 mpg is it for me. ..Willy.