Propane issues on a 20r

Lauderdale · Sep 1, 2014

My friend has a 20r setup on propane. He traded for it ran great the first few days. Then just began running awful. I've fooled with it but I have no idea about propane. It wasn't running at all. I set the timing wide open, and now it idles and creeps around fine. As soon as you get some speed up it starts shuttering and not wanting to maintain speed. Let me know what yall think. It doesn't have a mixer on it.

Fire Freak · Sep 1, 2014

What do you mean it doesn't have a mixer on it? pictures!

Technician · Sep 1, 2014

It has a mixer

Technician · Sep 1, 2014

Has to

Nuts · Sep 1, 2014

Maybe its :afro: rigged and just has a propane hose from the tank to the carb? :dunno:

altfuel1991 · Sep 2, 2014

Can you please define "set the timing wide open" for me. Propane has some general guidelines for timing that will work and get it close but wide open is not one of them. Here are the general guidelines:

On most applications, the timing should be a total of 30 degrees(base and centrifugal) with all of it in by 2500 rpm. What we normally do is disconnect the vacuum advance, run the engine up to 2500 rpm, set the timing at 30, lock it down, then let it idle with the vacuum advance disconnected. See what your base timing is running. If it is low,4-10 degrees for example, you can alter the centrifugal to lower that number and increase the base, still keeping a total of 30 degrees. As you increase the base timing check to see if the engine spins and starts smoothly when hot. If you reach a point that the engine bucks or loads the starter, back off about 3-4 degrees and that is your base timing. Subtract that number from 30 degrees and that will be the advance you need to have. This will provide a good start, strong idle and proper advance curve. We have had some engines run as much as 20 degrees base timing but 14-16 degrees is normal. The vacuum advance should be connected to ported vacuum and have no more than 10 degrees. This helps fuel economy at light throttle positions.
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Can you provide info on what brand components are on this truck? That would help figure out what is going on with it. Or if you could post photos that might help also.

buggy68 · Sep 2, 2014

pics ? curious whats going on with no mixer!

TacomaJD · Sep 2, 2014

I hate that everybody calls the vaporizer a "mixer" The vaporizer is NOT the mixer. It is a diaphragm operated device that controls fuel flow based on vacuum, and the engine coolant runs through it, in order to heat up the liquid propane and turn it into vapor...hence the name VAPORIZER! It also regulates the fuel flow down to a much lower psi before it enters the carb.

The correct reference for "mixer" is actually the propane carburator itself, that's mounted to the throttlebody. They do two totally different things. Actually all carbs are "mixers" for that matter, as they all mix some form of fuel with air.

Since it does not have a VAPORIZER, and only has a liquid propane line running straight to the carb, it's not vaporizing the propane before it enters the combustion chambers and I would assume most engines usually don't have the compression to combust straight liquid propane and run smoothly. My propane engine always seems cold natured until it warms up, when the engine warms up, the propane begins to vaporize as it passes over the heating fins inside the vaporizer that are heated by the engines coolant. Plus it would be an unregulated fuel flow into the carb, since the vaporizer also regulates that too. Also, fuel and air mixture is something else.

I think you are chasing your own ass troubleshooting this without a vaporizer. :dblthumb:

TBItoy · Sep 2, 2014

TacomaJD said:
I hate that everybody calls the vaporizer a "mixer" The vaporizer is NOT the mixer. It is a diaphragm operated device that controls fuel flow based on vacuum, and the engine coolant runs through it, in order to heat up the liquid propane and turn it into vapor...hence the name VAPORIZER! It also regulates the fuel flow down to a much lower psi before it enters the carb.

The correct reference for "mixer" is actually the propane carburator itself, that's mounted to the throttlebody. They do two totally different things. Actually all carbs are "mixers" for that matter, as they all mix some form of fuel with air.

Since it does not have a VAPORIZER, and only has a liquid propane line running straight to the carb, it's not vaporizing the propane before it enters the combustion chambers and I would assume most engines usually don't have the compression to combust straight liquid propane and run smoothly. My propane engine always seems cold natured until it warms up, when the engine warms up, the propane begins to vaporize as it passes over the heating fins inside the vaporizer that are heated by the engines coolant. Plus it would be an unregulated fuel flow into the carb, since the vaporizer also regulates that too. Also, fuel and air mixture is something else.

I think you are chasing your own ass troubleshooting this without a vaporizer.

hell he may be running a vapor draw bottle

TacomaJD · Sep 2, 2014

Lol There is no telling. I wanna see pics!

TBItoy · Sep 2, 2014

TacomaJD said:
Lol There is no telling. I wanna see pics!

Hell, it may have a couple grill bottles and regulators T'd together to a hose-pipe duct taped into the airbox :fish:

altfuel1991 · Sep 3, 2014

It is going to have a mixer and a vaporizer on it. It may not have a lockoff valve on it though.

Lauderdale · Sep 3, 2014

I'm trying to get pictures, but he won't send them. It has a vaporizer. I didn't know that was the term for it. The bottles he's running are just your. BBQ grill bottles.

TacomaJD · Sep 3, 2014

Lauderdale said:
I'm trying to get pictures, but he won't send them. It has a vaporizer. I didn't know that was the term for it. The bottles he's running are just your. BBQ grill bottles.

That's the problem. That's a vapor tank, they'll run the engine, but won't supply enough fuel to run it like it's supposed to. You need a bottle that has a LIQUID valve on it. The liquid valve will have a pickup inside the tank that delivers LP to the tank outlet, like a gas tank on cars/trucks. Get the right bottle, problem will likely be solved.

TacomaJD · Sep 3, 2014

Or, in the meantime, turn your existing tank upside down so the LP will be forced to the outlet via gravity. Then troubleshoot timing and all that....and find a proper tank.

Lauderdale · Sep 3, 2014

Thanks. We'll see what that does. I've got him a carb coming. He's going to be running it on the roads.

Lauderdale · Sep 3, 2014

TacomaJD said:
Or, in the meantime, turn your existing tank upside down so the LP will be forced to the outlet via gravity. Then troubleshoot timing and all that....and find a proper tank.

Thanks again flipped the bottle over. He said, "It runs like a raped ape!" He's on his way to get a bottle right now.

TacomaJD · Sep 3, 2014

It's all about understanding how it works, glad he's on the right track now. I chased a problem with mine for about 3 weeks not too long ago, that turned out to be a faulty diaphragm in the mixer/carb. Positive side to that is, now I understand 100% of how my propane system works now, and did not know much of **** about it when the problem first showed it's head. :dblthumb: