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Postby Comrad » Mon Nov 10, 2014 8:41 am

Is anyone here running/familiar with autogas? My 1976 4x4 F250 is a 351c petrol/gasoline engine. Its had a conversion done so it runs duel fuel, petrol/gasoline and autogas/propane.

I quite enjoy having the gas on board, it adds to my fuel storage, plus it cuts down on cost. Accounting for currency and volumetric conversions, "gasoline" prices where I live are roughly $6.40 a gallon, as opposed to autogas which is roughly $3.90 a gallon. I don't get nearly the same amount of power per volumetric measure of autogas as I do with petrol, but my "back of the envelope" calculations suggest that there's a definite economical benefit to using the autogas.

Is anyone else familiar with autogas? I'm having a slight issue at the moment where I feel like the engine is struggling a little, like its misfiring when I put it under load, or try to take off in second gear. I remember a mechanic telling me once when I was still a kid with an autogas car, and knew nothing about working on cars, that autogas is harder to ignite than petrol, so any issues with your ignition system are likely to be noticed earlier when you have autogas. I remember him saying it was one thing in particular - I just cant remember what it was. Obviously its either distributor, leads, or spark plugs, I just can't remember which. Does anyone here know?

Also, while I'm on the topic, has anyone ever water-proofed a "gasoline" vehicle? I want to be able to cross the same rivers, etc... that the diesel vehicles do. I usually just coat the distributor with WD-40 and hope for the best, but, I've heard of people sealing the distributor with silicone and installing a high-mount breather tube. Does anyone here have any experience/resources with this.

Thanks guys, sorry for all the questions. Hope someone can help out.
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Re: Autogas

Postby LostSkillsPodcast » Sat Nov 15, 2014 2:05 am

it sounds like you are having spark knock issues. it sounds like you need to retard the ignition timing when you use propane.
here is a little info to help you
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Re: Autogas

Postby Agcoach » Sat Nov 15, 2014 11:08 pm

Its not propane, but I am running a truck on compressed natural gas (CNG). Same 16 mpg on gasoline or cng. And its $1.65/ gal equivalent here. Three years and the truck has paid for its self in fuel savings alone.

Good luck with yours
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Re: Autogas

Postby Comrad » Sun Nov 16, 2014 9:34 pm

Thanks for that link, Jeff, I didn't really know about spark knock.

The thing about it for me is that it didn't always happen, its only started recently. This sort of rules out a bunch of those causes on the link, except for maybe the idea that I need to clean out the carburetor to ensure my air-fuel ratio is still correct. It's not like I've changed anything on the vehicle with regards to ignition/fuel recently.

I did a quick inspection of my leads and distributor on the weekend, and couldn't really see anything. I was considering upgrading them anyway. I was going to replace all the leads and spark plugs, and keep the old ones on board as spares. I was also thinking of sealing the distributor cap with sikaflex and tapping in an air fitting going to a compressor to create positive pressure inside the distributor with a breather hose going up higher on the vehicle. I'm planning on going to some pretty remote places in the outback of Australia, so I might have a few river crossings to go through. I'm slowly building it up to tackle anything.
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