Natural gas conversion - where to feed the gas

[square1]

Subscribed. Hope to learn more about the Petro to NG conversion. Specifically my question is about starting the generator on Petro and then switching to NG once running. I understand without electric start it's nearly impossible to get one stated on NG.

 

[Rocky J]

Subscribed. Hope to learn more about the Petro to NG conversion. Specifically my question is about starting the generator on Petro and then switching to NG once running. I understand without electric start it's nearly impossible to get one stated on NG.

Some regulators have a primer button you push to manually hold the diaphragm open like the one Travelover has per the youtube video he attached, you could compare it to a choke on a gasoline carburetor . On forklifts, automobiles they have a electric solenoid mounted over the primer button so when the electric starter is activated the solenoid pushes and holds the button down until you stop using the starter . Some regulators like Travelover has do not have the built in safety valve that takes a second small vacuum hose , this shuts off the vapor if the engine was to quit. To use the device indoors it is normal to have, so there is a whole different device that looks like a regulator but is a safety fuel shut off that should be but will still work with out, it is mounted between the tank/fuel supply and the regulator and has a small vacuum hose that is ported in somewhere between the throttle plate and the engine block for constant vacuum. With all this going on some can be hard to start, My loader has a V4 Wisconsin and I start it on gasoline , it has a electric fuel pump with a switch on it , after it starts I shut off the fuel pump and when it starts surging running out of gasoline I turn on the propane bottle , not a exact science if I am a little early it just blows black smoke and runs bad for a few seconds.My guess is that it is the engine is wore out and not enough vacuum to open and draw the propane until the RPM's are higher then the starter can turn.

 

[Travelover]

Subscribed. Hope to learn more about the Petro to NG conversion. Specifically my question is about starting the generator on Petro and then switching to NG once running. I understand without electric start it's nearly impossible to get one stated on NG.

Some regulators have a primer button you push to manually hold the diaphragm open like the one Travelover has per the youtube video he attached, you could compare it to a choke on a gasoline carburetor . ...........

Rocky nailed it - the primer button holds the diaphragm open and allows the gas to purge the air in the lines. There are dozens of YouTube videos on this and in many, they just hold the primer button in until they can smell gas. Then pull the rope or engage the starter and you are ready to go. Without a primer, you'd need to crank it a long time especially if you had a lengthy hose.

 

[Travelover]

So, I got a new used manifold yesterday off eBay. Can I feed the natural gas directly into the manifold? It seems like there is a good vacuum there - that is where vacuum is pulled on a car to operate brakes, etc. What would be the minimum diameter barb for an 11 HP engine?

 

[Rocky J]

So, I got a new used manifold yesterday off eBay. Can I feed the natural gas directly into the manifold? It seems like there is a good vacuum there - that is where vacuum is pulled on a car to operate brakes, etc. What would be the minimum diameter barb for an 11 HP engine?

Do you mean with out a carburetor ? If so the answer is no. It needs to use the throttle plate in the carburetor. The Inside Diameter on my hose from the regulator to the carb is 3/8 inch , so you need to know what size pipe thread is in your regulator or take it with you to the hardware store. If I was guessing it would be 3/8 npt (national pipe thread) to 3/8 hose barb, the hose is not under pressure so any thin flexible hose will work . It is important that your hose ends up between the carb and the air filter in the air filter box, it needs the negative pressure that will not be on the other side of the filter. other then drilling a hole big enough to get that hose into the air filter box you will not alter anything else from a normal running gasoline engine, in fact if you run out of propane turn on the gasoline and start it back up.

 

[Travelover]

Do you mean with out a carburetor ? If so the answer is no. It needs to use the throttle plate in the carburetor.

No, I'm leaving the carburetor in place so it can also run on gasoline if need be. I'm proposing drilling and tapping the manifold between the carb and the engine and installing a barbed fitting to attach the gas hose.

The Inside Diameter on my hose from the regulator to the carb is 3/8 inch , so you need to know what size pipe thread is in your regulator or take it with you to the hardware store. If I was guessing it would be 3/8 npt (national pipe thread) to 3/8 hose barb, the hose is not under pressure so any thin flexible hose will work .

Yes, the outlet of the regulator is 3/8" NPT. My question was, "what is the necessary inside diameter of hose between the regulator and the engine". It sounds like you were successful with 3/8"

It is important that your hose ends up between the carb and the air filter in the air filter box, it needs the negative pressure that will not be on the other side of the filter. other then drilling a hole big enough to get that hose into the air filter box you will not alter anything else from a normal running gasoline engine, in fact if you run out of propane turn on the gasoline and start it back up.

Why would the gas inlet point need to be between the carb and the air filter as opposed to directly into the manifold as described above? With the carburetor installed, there is a vacuum (negative pressure) in the manifold.

 

[Rocky J]

The throttle plate in the carburetor is going to control the amount of vacuum on the Regulator , it is a Demand Regulator , more vacuum = more fuel , this regulator is like a carburetor supplying the right amount of fuel to air mix . In the intake between the carb and engine block is constant high vacuum and would give it uncontrolled amount of fuel to air mix, if it did start it would be like the choke full on when running on gasoline. If you look inside the gasoline carburetor you will see the tube the gasoline comes out of is in-between the throttle plate and the chock plate , this regulator needs to be separated from the engine with the throttle plate .

 

[Travelover]

The throttle plate in the carburetor is going to control the amount of vacuum on the Regulator , it is a Demand Regulator , more vacuum = more fuel , this regulator is like a carburetor supplying the right amount of fuel to air mix . In the intake between the carb and engine block is constant high vacuum and would give it uncontrolled amount of fuel to air mix, if it did start it would be like the choke full on when running on gasoline. If you look inside the gasoline carburetor you will see the tube the gasoline comes out of is in-between the throttle plate and the chock plate , this regulator needs to be separated from the engine with the throttle plate .

Good explanation, thank you. I'll need to figure out a way to feed the gas into the air cleaner box just in front of the carb inlet to be sure I have an adequate pressure drop.

 

[Travelover]

The picture below is what is under the paper air filter. There is an offset plate covering the carburetor inlet that extends down to the lower right to cover the crankcase breather tube inlet. I think that plate helps increase the vacuum at the inlet of the breather tube. I'm thinking of tapping a hole in the upper left corner for a natural gas inlet barb and extending the existing plate over the barb base inlet. This extension should give me additional vacuum at the gas inlet.

Does this sound reasonable?

 

[Rocky J]

This is what I did, yes it egg shaped the hose a bit.