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Discussion Starter · #1 ·
All,

I got the parts set up for my old rotary generator to run it on propane but I'm having issues with it. I can't get the engine to fire.

A few details -
The gas manifold sits under the carb.
The regulator is a Garretson KN style

The propane hose from the tank (using a bit thats left in a 20lb tank, maybe the last 1/4 of the tank) is fed with an adjustable pressure regulator. I set it to 5lbs. The low pressure reg on the generator hums with the gas on and when I push the prime button on the back of the regulator the humming stops.

The hose from the regulator to the manifold under the carb is temprary. I cut a shorter piece but I can't find it at the moment so I just threw on the rest of the coil I had to test it.

I have a couple "load blocks". One is an adjustable needle valve. I didn't think I was getting enough gas through it so I pulled it out and used my bolt/elbow contraption to try to get more gas flow. I adjusted it a few times opening it further. Still can't get the engine to fire.

For what it is worth, in the beginning I set the propane up without the hose between the regulator and manifold. I could smell propane coming out of the regulator so I assumed it was working. I am not sure about the humming though.

Ideas?

Picture is with the needle valve plumbed in. Black hose is between the regulator and manifold. Stainless braid sheath hose is the supply from the tank.
9499
 

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Your set up requires two regulators.
One at the tank and your KN at the generator.
Hopefully you do have both installed.
If not you have possibly damaged the Garrison KN.
 

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Discussion Starter · #3 ·
Your set up requires two regulators.
One at the tank and your KN at the generator.
Hopefully you do have both installed.
Re-read what I wrote.

The propane hose from the tank (using a bit thats left in a 20lb tank, maybe the last 1/4 of the tank) is fed with an adjustable pressure regulator. I set it to 5lbs. The low pressure reg on the generator hums with the gas on and when I push the prime button on the back of the regulator the humming stops.
 

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Discussion Starter · #4 ·
Looking in to it here... I see on Garrettson's site the max inlet pressure is 13.84 inches of WC. That doesn't make sense. That calculates out to less than 1/2 PSI.

I thought the outlet pressure was supposed to be between 10-14 inches of WC. If the inlet pressure is less than that you can't get that output pressure?
 

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Discussion Starter · #5 ·
This is a close-up of one of the regulators. I got 3 of them, 2 to use and a spare/possibly put on another unit, but wasn't in the cards when I ordered them. Maybe down the road.

In any event, these are the ones without the adjustment screw - the opening (above the inlet port and below the "mount up" words) where the screw would be is blocked off.

9500
 

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the garretson is not to regulate down any pressure.
it is a demand safety regulator only.

the inlet pressure needs to be about the 11-13 wc to the demand regulator. and yes on the less than 1/2 a psi!
so you can tell if the demand regulator output is flowing with out the engine connected the main regulators pressure is way too hot on the inlet pressure. it will push flow past the valve in the demand regulator at 13-15wc or higher.
the slight suction on the carb adaptor hose trips the flow to on.

and most load blocks for a 200cc to a 390cc engine use a 3/8 dia bolt with mostly open flow.

also run a shorter line from the demand regulator to the carb plate.
you want that at 2 foot as max length...
shorter is more responsive for loads.
 

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Discussion Starter · #7 ·
Apparently I did not cut the shorter hose as I thought I did - I measured the hose I had and it was the 6ft I bought originally. Then I found the mark on the hose where I had sized it up from before, but again.. never cut it. In any event, I got the hose shorter.

I was not able to get the generator to run right off of propane today, however I thought I would fire it up on gas then switch it over to see if it would run - and it does.

So now a mystery - if it runs on propane but won't start on it - what am I doing wrong, if anything, on this unit?

For what it is worth, the load block tuning is a bit finicky. With a load I can get the RPM's to settle in. Light to no load and the RPM's hunt a bit.

Another tidbit is the initial pressure regulator (picture attached this round) has to be all the way closed to get the right mix to the regulator on the generator - at least at the moment. I thought "off" meant "off", but when I was tweaking it having the pressure regulator on the tank all the way closed down is where I got the best running on the engine - plus the tuning of the load block.

9504


9505
 

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Discussion Starter · #8 ·
Talking with a buddy of mine I got to thinking about the manifold placement.

On the GX690 the gas manifold sits above the carb - between the carb and air filter housing - and starts on propane no problem. On the small engine here the gas manifold is between the carb and engine block. I can change that. The order doesn't physically/part-fitment-wise matter - I can easily swap them. Would it be worthwhile to try swapping them? Or is there something I am messing up in the "flow" of things by setting it up how I have it?

For what it is worth, there is another hole that the gasket between the carb and air filter housing has right next to the intake hole between the mounting bolts. I am not sure what it is for, nor did I pay attention to see if that was on the engine block side of the carb.
 

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it need to be in front of the carb.
or have a carb that is setup for gasious fuel.
what engine is on this gen set?
and how many cc?
 

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Discussion Starter · #12 ·
I will keep hammering the set up for a bit and see what I can come up with.

The picture below is from the air filter side of the carb. When I initially put the manifold (under the carb as I'm holding it) on it was between the carb and engine block. I switched it around to sit between the carb and air filter instead.

Question - what does the hole that the red arrow head sits over do? I did not take that in to account when I made the manifold and the manifold blocks it. The hole vents to the air filter housing. The manifold sits over top of it blocking it. However, the engine starts and runs on gasoline and the engine will run on propane - once started on gasoline. I just can't get it to start off on propane.

9526


Here are a few more pictures of the part fitments.

If you reverse the image of the carb face above, you can picture where the matching notch is in the air filter housing below:

9527



Here is how the manifold sits on top of the carb - on the air filter side where I moved it to.
9528


Something that strikes me a bit when thinking through the issue - vacuum is what draws the fuel (in this case, propane - natural gas also works the same way, really as does gasoline - just from a different port) in to the intake. When I prime the carb with propane (using the prime button on the regulator to shoot gas straight through, as opposed to the vacuum drawing from the regulator as it would when running normally) I am not able to get the engine to fire off to start. Is it possible that I am drawing too much air and not getting enough draw of the propane through the system? Should the fuel line be blocked off so it does not "vent" and cause a vacuum leak when I am trying to get the propane/NG to draw through the carb? Is there anything else I need to block to get the draw on the propane up?

When I start on gasoline the engine is already running so the draw through the carb is already in place. Therefore, when I switch to propane there is already a strong vacuum - more so than I would be able to generate pulling the cord start. So the idea of too much air and not enough fuel getting in on start up tends to make sense - the vacuum through the carb when it is running allows me to get enough vacuum to be able to tune the gas draw from the load block, but no matter what I do I can't get enough draw through the carb to start it.... ?
 

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drill the bowl vent port as a feed through
and then use a solid gasket from the plate to the carb inlet.
use the old carb gasket on the plate to the air filter box.

you will have to have the air filter in place for this to start and run right.
the air filter sets the intake flow resistance to make the demand regulator trip for flow.

also a slight taper on the inside of the adapter helps.
and an angle on the flow nipple.

some where i have pix on this.
 

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Discussion Starter · #14 ·
drill the bowl vent port as a feed through
Is the vent port on the bowl the bolt that is at an angle, not the one on the very bottom?

I'd rather not modify the carb other than maybe blocking ports (like the gasoline inlet if that is what is causing the vacuum to not be enough to start on propane). That was the reason for the separate gas manifold - to give a place where propane/NG could be injected in to the intake stream without modifying things much.

I understand the idea of the air filter being in place to help with establishing enough vacuum.

The question is, I think... What is preventing the vacuum on start up on propane but it works on gasoline? If air can get through from the gasoline line (by not being blocked off) that is one idea. Though, there is a vacuum fuel pump and the end of the intake line has a marine fitting that is closed when not connected = blocked. The vacuum line (that gives the pulsing for the pump to run) goes to the OHV cover. I don't think that line would allow any air through to the fuel port on the carb.

Another question - on generators that are dual fuel with a selector "switch" or "knob" - what happens when you move the position from gasoline to propane? I know some of them have electronic fuel solenoids on the carb that will block the gasoline flow. What else, mechanically, if anything, is happening when the selector is switched to propane?

On my EU2200i the on/off rotary dial has a 3ord position that pinches off the gas line so that you can run the gas out of the carb for storage, for example. If you go all the way to off it will cut the ignition and kill the engine immediately. That is good for restarts soon after, but it leaves the carb primed and that fuel sitting in there can gunk up over time - hence the 3ord position to cut the fuel off and let the engine run all that fuel in the carb out = so it doesn't gunk up as easy.

I am assuming there are multiple things happening with those fuel selectors on generators that have that dual fuel set up. What are those things?
 

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you will be drilling that new mfg plate!
not the carb!

and the air filter as restriction is the only way a plate style setup will work.
 

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Discussion Starter · #16 ·
I worked on the natural gas side today with the generator. I also tried a few things with propane trying to get it to start. I tried blocking off the gas line and the OHV cover breather tube - the only 2 "vents" I could figure, besides the air filter.

I also moved the manifold back under the carb - between the carb and the intake on the block. The reason I did this was 2 fold -
1. The manifold doesn't have the additional access hole that the arrow points to in an earlier post. By putting the manifold under the carb the original porting works between the carb and air filter.
2. The choke plate at the front of the carb is to restrict the air draw. With the gasoline fuel line and bowl in place the choke plate closing creates more vacuum on the fuel draw, thus more fuel can be pulled in to the engine. With the gas hooked up to the manifold on top of the carb - on the air filter housing side - the choke is underneath the gas injection point. So when the choke is on there is no additional vacuum on the gas draw, in fact the exact opposite is true - less draw is there because there is less draw from the air filter - which is where the gas is being injected to. By putting the manifold under the carb the choke closing will cause more vacuum on the gas port thus drawing more gas in to the intake.

With all that having been said, I was still unable to get the engine to fire off on propane. I didn't even bother with trying to start on natural gas - I assume it would only be more difficult.

However, I did hook up the natural gas line and get the engine running on it after starting with gasoline. The generator is quite weak on it, but lower power output on natural gas is par for the course. As to the exact wattage reduction - I am not real sure. I did not measure it. However, it does run!

I would assume the engine would run stronger if I had a higher volume gas line to pull from. That is just an assumption. The big generator (15kw) won't run on natural gas through the regulator normally, but will with the primer button held open = bypassing the regulator. I'm assuming there just isn't enough gas behind the regulator to make it do what it needs to do how it needs to do it.

Note the needle nose pliers pinching off the gas line. That was for 2 reasons - to stop the gasoline flow and to block that line from venting causing less vacuum on the natural gas. I turned on the natural gas slow once the gasoline was starting to run out of the bowl. It took a bit of tweaking of the load block but it does run.
9529
 

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Discussion Starter · #17 ·
Update -

We had the gas feed upgraded with a tap right off the meter (1" line). I mentioned that in another thread a while back now, maybe a couple months ago.

I went through the motions to get this older/smaller open frame unit set up to run on the natural gas a couple days ago. I had trouble getting it to start so I went back to the "start on gasoline and switch over" trick - that never fails. Once I got things switched over to natural gas I tuned the load block. I set the mix a tad rich at a pretty high load and it seems to work pretty good. With the load block tuned there I can get the generator to start on natural gas now. However, it does take a lot of work to get it to go. It takes a few rounds of priming, pulling the starter cord, and repeat. Once it fires it barely chugs along at first. I have to feather the primer on the regulator for a bit to get the engine to come up to running speed. Once it is at running speed there is enough draw through the carb to get the regulator to run. If the engine is not up to operating speed it doesn't have enough vacuum to work the regulator.

What I don't know is if the generator will start cold like this. I had already got the unit running on gasoline so it was warmed up when I did this. However, it was relatively reliable - reliable in the fact that I could always get it going again on NG, but "relatively" because of the challenges with it struggling at first until it gets up to speed.
 

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yea.....
hummm
welll..
where to start?
lol
this was your home made conversion plate right?
 
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