Generator on Propane/NG Issue

northerner · October 2013

I converted my EU 2000 to run on three fuels (gasoline, propane and natural gas) through a conversion kit sold by Central Maine Diesel. This is accomplished by drilling the carb and inserting a tube with hose attachment to the propane or natural gas source, and by installing a shutoff valve for the gasoline. The fuel for the propane or NG is controlled by an on demand regulator, that uses carb vacuum and a large silicone diaphragm to control the amount of fuel flow through the regulator. If there is no vacuum (ie engine quits running) the fuel is shut off.

With the advent of cloudy weather and shorter sun days, I attempted to get it going on propane for now. Initially, I couldn't get it running last night, so I just ran the generator on gasoline for an hour or so, to give the batteries a boost. This morning, I decided to take apart the on demand regulator, and installed a new rebuild kit (diaphragm, valve, springs, etc...) even though the existing parts looked OK. I did this as I accidentally hooked it up directly to a propane tank a while back, and thought I may have compromised the diaphragm with the high pressure. I have a primary regulator in place now, that brings the tank pressure down to about 1/2 psi or so.

With the generator operating this morning, I initially could only get about 1300 to 1400 watts max out, and that was with the load block turned all the way out. It has increased since, as it's warming up a little outside (went from about 8c to about 12c now) and I'm currently putting out about 1600 watts. I'm running off a 20 lb tank that is about 1/2 or more full. Could it be that there is insufficient vaporization that is limiting the output? Or perhaps the primary regulator is dropping the pressure too low?

I also attempted to start the gen on natural gas last night, and I couldn't get it to fire at all, whereas the propane at least showed signs of firing with the load block adjusted all the way out. That's why I was figuring there may have been an issue with the on demand regulator. The instructions say that the load block (mixture screw) on the output of the on demand regulator should be set approximately 1/4 turn out for every horsepower. I have it turned out in excess of 10 turns. I know that EU 2000 is peppy now, but it doesn't put out that kind of power.;)

westbranch · October 2013

Re: Generator on Propane/NG Issue

Hmmmm, when I ran my 78 Ford P/U on propane it never falter till temps dropped well below 30 below. It had a heater in the vaporizer but the engine had to warm up first, helped at low temps. Mind you I just did the normal 5 min warm up in the winter anyway gasoline or propane.

So it may be that you have too little output pressure from the regulator. Can you adjust it?

You should see some derating from gasoline to propane as there is less caloric value in propane.

Does that tank have one of those new OPD Valves, (with the internal and external threads), if so you need a shutoff in the outlet line after the regulator as it will choke off the flow thinking there is a leak.

TIP, they have to be opened VERY slowly... or they shut sown, but not supposed to, BBQ will barely start...

northerner · October 2013

Re: Generator on Propane/NG Issue

I believe the regulator can be adjusted and may be the problem. No problem with gas coming out of the tank as I tested that and it's running fine now. Just that the load block is adjusted way out. Funny though I couldn't get it to fire at all on natural gas last night. Could have also been a problem with the diaphragm.

northerner · October 2013

Re: Generator on Propane/NG Issue

The problem isn't with the primary/secondary regulator. I tried pushing in the priming button on the on demand regulator, and that floods the engine. So plenty of gas available. It's running fine now, just an issue with the load block adjusted out really far for proper operation. There is an adjustment for the spring on the diaphragm controlled valve, but it's locked in place and I can't turn the cap. Looks like it's factory set. I do notice that it's turned in further than as shown on a picture of it. This means that there's a little more spring tension on the valve and is more difficult to open from vacuum pressure.

northerner · October 2013

Re: Generator on Propane/NG Issue

I'm finding the same issue in attempting to use the on demand regulator with natural gas in that I'm only getting about 1/2 the power from the generator maximum, and is difficult to start. Again the problem is with the spring tension on the diaphragm of the on demand regulator is too much, and as result the vacuum pressure from the carb doesn't open the valve in the on demand regulator enough to obtain full speed operation. I verified this by pushing in the priming button while running (which is a way to manually open the valve) and the engine picks up speed. Putting in a lighter spring should solve the problem. Anyone else out there have experience with running on natural gas?

NorthGuy · October 2013

Re: Generator on Propane/NG Issue

I wonder if the gas pressure in the pipe is high enough?

papa · October 2013

Re: Generator on Propane/NG Issue

northerner, Couple of questions.

1.) On small, multi-fuel units, the carburetor typically isn't drilled. Instead, a separate venturi 'adapter' is installed between the carb intake and air cleaner. So this begs the question... Where, exactly on the carburetor, did you 'drill' it?

2.) How far is the demand regulator mounted from the carburetor? And is it mounted vertical (as opposed to a pancake laying horizontal)?

Iceni John · October 2013

Re: Generator on Propane/NG Issue

The Garretson KN demand regulator needs a gas pressure of 11" WC which your main regulator should always be supplying. Different models of KN are factory-set to different pressures - you should never need to touch those settings provided you have the right model for your application. Is the KN mounted vertically? Do you have sufficient flow rate through its supply pipe? Is it mounted too far from the carburetor? Is the load screw set correctly on the load block - if it's unscrewed too far it will run far too rich. Are you are high altitude? Do you have any air leaks in the carburetor?

I recently installed an LPG conversion kit on my Champion 3500W generator in my bus, and it works fine even under full load. It does however only start on the third pull, presumably because the carb is sucking gas through from the KN on the first and second pulls. Mind you, it never fails to start on the third pull now, hot or cold, just like it always started on the first pull with gasoline. I have 1/2" flexible stainless gas pipe running from the main two-stage regulator to the generator, via a distribution manifold and a quick-connect, but everything is 1/2" to allow sufficient gas flow.

John

northerner · October 2013

Re: Generator on Propane/NG Issue

NorthGuy wrote: »

I wonder if the gas pressure in the pipe is high enough?

Gas pressure is high enough to run an 80, 000 btu furnace, plus hot water tank range and another 10,000 btu heater in my workshop. I did the test with the other devices off, so that shouldn't be a factor affecting the pressure. I have it piped in to the on demand regulator with 1/2 " gas pipe and flex line, and the line is quite short. So I don't think gas pressure is an issue. Particularly when I push in the priming button on the regulator, engine picks up speed to near normal.

northerner · October 2013

Re: Generator on Propane/NG Issue

papa wrote: »

northerner, Couple of questions.

1.) On small, multi-fuel units, the carburetor typically isn't drilled. Instead, a separate venturi 'adapter' is installed between the carb intake and air cleaner. So this begs the question... Where, exactly on the carburetor, did you 'drill' it?

2.) How far is the demand regulator mounted from the carburetor? And is it mounted vertical (as opposed to a pancake laying horizontal)?

I ordered the carburetor from Central Maine Diesel and they drilled out the carb, so I assume that part was done properly. It ran fine on propane in any case. The demand regulator is very close to the carb, and mounted on the access panel, and is mounted vertical. The one thing I noticed about the regulator, is that the screw for adjusting spring tension on the diaphagm assembly and valve, is turned in quite a distance, meaning more vacuum pressure is required to open it. On pictures of the regulator, the screw appears to be turned out farther. Perhaps a manufacturing issue. I'm looking at either putting in a lighter spring or shortening up the existing one. I'm sure that will solve the problem.

northerner · October 2013

Re: Generator on Propane/NG Issue

Iceni John wrote: »

The Garretson KN demand regulator needs a gas pressure of 11" WC which your main regulator should always be supplying. Different models of KN are factory-set to different pressures - you should never need to touch those settings provided you have the right model for your application. Is the KN mounted vertically? Do you have sufficient flow rate through its supply pipe? Is it mounted too far from the carburetor? Is the load screw set correctly on the load block - if it's unscrewed too far it will run far too rich. Are you are high altitude? Do you have any air leaks in the carburetor?

I recently installed an LPG conversion kit on my Champion 3500W generator in my bus, and it works fine even under full load. It does however only start on the third pull, presumably because the carb is sucking gas through from the KN on the first and second pulls. Mind you, it never fails to start on the third pull now, hot or cold, just like it always started on the first pull with gasoline. I have 1/2" flexible stainless gas pipe running from the main two-stage regulator to the generator, via a distribution manifold and a quick-connect, but everything is 1/2" to allow sufficient gas flow.

John

John, The KN is mounted vertically and close to the carburetor. I've tried adjusting the load block throughout the whole range and no success. Pushing in the priming button a little, however, does allow the generator to run at nearly full speed. Also, it runs fine on propane. I'm located about 2000 feet above sea level, so not really at high altitude. So I'm thinking it's an issue with the KN regulator.

NorthGuy · October 2013

Re: Generator on Propane/NG Issue

northerner wrote: »

Gas pressure is high enough to run an 80, 000 btu furnace, plus hot water tank range and another 10,000 btu heater in my workshop. I did the test with the other devices off, so that shouldn't be a factor affecting the pressure. I have it piped in to the on demand regulator with 1/2 " gas pipe and flex line, and the line is quite short. So I don't think gas pressure is an issue. Particularly when I push in the priming button on the regulator, engine picks up speed to near normal.

Different utilities require different gas pressure. In the garage, I have 6 WC for the furnace (60,000 BTU) and generator (260,000 BTU). In the house, I have 10 WC for several appliences. I set it higher because of tankless water heater (180,000 BTU), which requires 9-11 WC. You can change your pressure by adjusting incoming regulator, which is usually next to the meter.

northerner · October 2013

Re: Generator on Propane/NG Issue

NorthGuy wrote: »

Different utilities require different gas pressure. In the garage, I have 6 WC for the furnace (60,000 BTU) and generator (260,000 BTU). In the house, I have 10 WC for several appliences. I set it higher because of tankless water heater (180,000 BTU), which requires 9-11 WC. You can change your pressure by adjusting incoming regulator, which is usually next to the meter.

So I take it, you can purchase a meter to actually measure the gas pressure? I do believe that the standard gas pressure is about 6 WC and that's roughly what is required for my on demand (KN) regulator. Sounds like this problem is an issue with that regulator.

NorthGuy · October 2013

Re: Generator on Propane/NG Issue

northerner wrote: »

So I take it, you can purchase a meter to actually measure the gas pressure? I do believe that the standard gas pressure is about 6 WC and that's roughly what is required for my on demand (KN) regulator. Sounds like this problem is an issue with that regulator.

Sure. Something like this.

Here's a picture of mine for the generator. I bought it used on eBay.

papa · October 2013

Re: Generator on Propane/NG Issue

northerner wrote: »

I ordered the carburetor from Central Maine Diesel and they drilled out the carb, so I assume that part was done properly.

I have no experience with CMD, so can't speak to their experience. As I eluded to, the smaller, multi-fuel generator installs do not normally drill the carburetor. I will say that if it isn't drilled precisely within the crown of the venturi, then it will NOT pull sufficient fuel from the demand reg. The proper way to test this, is to install a manometer between the demand reg and the carburetor and measure the negative WC fuel draw in the line. You can buy or build one - many cheap & easy DIY manometers scattered around the web.

northerner wrote: »

The one thing I noticed about the regulator, is that the screw for adjusting spring tension on the diaphagm assembly and valve, is turned in quite a distance, meaning more vacuum pressure is required to open it. On pictures of the regulator, the screw appears to be turned out farther. Perhaps a manufacturing issue.

I have a KN demand on my 3.5kw Champion with the aforementioned adjusting screw head buried slightly over 1/4" below the case surface - mine runs fine.

papa · October 2013

Re: Generator on Propane/NG Issue

One more tidbit....

The proper way to adjust the load block (fuel adjustment), is to...

1.) Warm-up the engine then apply an estimated 50-70% load.
2.) Back-out (open) the load block screw until the engine RPM don't increase anymore.
3.) Slowly start closing the load block screw until the engine RPM just starts decreasing - reopen the screw slight and stop.

Ideally, on propane, the engine F/A ratio should be as LEAN as possible, but still achieve max RPM and load. If you run it too RICH, you'll toast the exhaust valve.

westbranch · October 2013

Re: Generator on Propane/NG Issue

Years ago we switched our propane BBQ to NG and had to resize the orifice of the jet...so it is possible they drilled it for propane only. If so, the diameter is probably about 50% too small.

northerner · October 2013

Re: Generator on Propane/NG Issue

papa wrote: »

I have no experience with CMD, so can't speak to their experience. As I eluded to, the smaller, multi-fuel generator installs do not normally drill the carburetor. I will say that if it isn't drilled precisely within the crown of the venturi, then it will NOT pull sufficient fuel from the demand reg. The proper way to test this, is to install a manometer between the demand reg and the carburetor and measure the negative WC fuel draw in the line. You can buy or build one - many cheap & easy DIY manometers scattered around the web.

I have a KN demand on my 3.5kw Champion with the aforementioned adjusting screw head buried slightly over 1/4" below the case surface - mine runs fine.

It could be that the carburetor wasn't drilled properly by CMD. I may look at getting a manometer. Mine is obviously not getting enough fuel on NG irregardless, as it picks up speed when the primer is depressed a little. Is the KN regulator adjusted for each generator? I'm sure your 3.5 kw Champion will have more vacuum capability than my small 1.6 kw Honda. I figured the regulator would adjust the flow dependent on the vacuum pressure, and thus work for any genset. There is an adjustment for the spring tension on the diaphragm, and appears they used lock tite to set it in place. (either at the factory or by CMD?)

northerner · October 2013

Re: Generator on Propane/NG Issue

papa wrote: »

One more tidbit....

The proper way to adjust the load block (fuel adjustment), is to...

1.) Warm-up the engine then apply an estimated 50-70% load.
2.) Back-out (open) the load block screw until the engine RPM don't increase anymore.
3.) Slowly start closing the load block screw until the engine RPM just starts decreasing - reopen the screw slight and stop.

Ideally, on propane, the engine F/A ratio should be as LEAN as possible, but still achieve max RPM and load. If you run it too RICH, you'll toast the exhaust valve.

While running on propane, I had it running as lean as possible. Thanks for that info!

northerner · October 2013

Re: Generator on Propane/NG Issue

westbranch wrote: »

Years ago we switched our propane BBQ to NG and had to resize the orifice of the jet...so it is possible they drilled it for propane only. If so, the diameter is probably about 50% too small.

This is a tri fuel kit ordered from CMD, and meant to run on gasoline, propane and natural gas. There is adjustment in the load block to compensate for the differences in propane and natural gas. I tried every adjustment while running NG, to no avail. Depressing the priming button (a manual control for the diaphragm controlled valve) did produce results.

papa · October 2013

Re: Generator on Propane/NG Issue

northerner wrote: »

Is the KN regulator adjusted for each generator?

Not that I'm aware of. To the best of my knowledge, the KN series has two offerings - a smaller HP unit w/7/16" dia. inlet orifice, and a larger HP unit w/1/2" inlet orifice. The specs are factory set and shouldn't need adjustment. The amount of engine vacume required to operate this demand regulator is typically measured in negative water column (WC), and is set at the factory to function at -0.5 or below w.c. (-0.12 kPa).

northerner wrote: »

I figured the regulator would adjust the flow dependent on the vacuum pressure, and thus work for any genset.

Not any genset, but yes, it works reasonably well across a broad engine HP size (Up to approx 40 HP for the smaller unit). However, if the engine has bad rings, low compression or a vacume leak, for example, its vacume will suffer and may not be sufficient to properly operate the demand reg.

There's a decent YT explaining the KN (although his numbers are inaccurate - he stated the WC as 6 inches which is not correct).

https://www.youtube.com/watch?v=CfM6D65MC_w

If I understand you correctly, it runs OK on propane?... yes? But does not accommodate NG?

This is frequently caused by too small of NG supply line, or the primary reg is too far from the genset. I would encourage at least 1/2" supply line between the gas company's reg and the KN @ up to 50' distance. The gas company's reg acts as the primary reg, so plumb it directly to the KN.

northerner · October 2013

Re: Generator on Propane/NG Issue

papa wrote: »

Not that I'm aware of. To the best of my knowledge, the KN series has two offerings - a smaller HP unit w/7/16" dia. inlet orifice, and a larger HP unit w/1/2" inlet orifice. The specs are factory set and shouldn't need adjustment. The amount of engine vacume required to operate this demand regulator is typically measured in negative water column (WC), and is set at the factory to function at -0.5 or below w.c. (-0.12 kPa).

Not any genset, but yes, it works reasonably well across a broad engine HP size (Up to approx 40 HP for the smaller unit). However, if the engine has bad rings, low compression or a vacume leak, for example, its vacume will suffer and may not be sufficient to properly operate the demand reg.

There's a decent YT explaining the KN (although his numbers are inaccurate - he stated the WC as 6 inches which is not correct).

https://www.youtube.com/watch?v=CfM6D65MC_w

If I understand you correctly, it runs OK on propane?... yes? But does not accommodate NG?

This is frequently caused by too small of NG supply line, or the primary reg is too far from the genset. I would encourage at least 1/2" supply line between the gas company's reg and the KN @ up to 50' distance. The gas company's reg acts as the primary reg, so plumb it directly to the KN.

When I mentioned this regulator will work with any genset, I meant gensets withing the range that this regulator was designed for (as you mention approx 40 hp) What I was trying to say is that the way it should work is adjust the flow for any size of genset (within the range of this regulator). My feeling is either there is a vacuum leak (which I will look for but don't suspect from a new unit that runs perfect on gasoline and propane) or that this KN regulator doesn't perfectly cover every generator and fuel types. I'm aware that NG is more difficult to run on.

My supply line is only about 20 feet or so from the house regulator, and half of that is 3/4" line, the other section to the genset is 1/2" as mentioned.

The key thing is when the priming button is depressed just a little further, engine speed picks up. This indicates that either the KN regulator or vacuum is the potential problem.

westbranch · October 2013

Re: Generator on Propane/NG Issue

If you can not see an obvious spot for the leak use a short shot of WD40 sprayed around the gasket, if the engine idle improves or changes, you now know where to look.....my old mechanic told/showed me that one for a leak on the intake manifold that was in a spot where you could not look at it...

hth

papa · October 2013

Re: Generator on Propane/NG Issue

northerner wrote: »

The key thing is when the priming button is depressed just a little further, engine speed picks up. This indicates that either the KN regulator or vacuum is the potential problem.

Perhaps, but not always. It only means that the engine prefers a richer mixture than what is being currently provided - question is.... why?

It could also be valve adjustment or ignition system deficiencies - LPG and NG has a higher ignition temperature, making them more difficult to ignite. So the ign system needs to be optimum. I would encourage a valve adjustment and spark plug replacement w/slightly narrow gap before replacing any fuel system components - especially if you plan on using either gasious fuel as primary. Without testing the fuel system with accurate gauges, you are shooting in the dark - I suspect you already know that.

northerner · October 2013

Re: Generator on Propane/NG Issue

I took a look inside the generator and found a few minor issues, each one likely contributing to the problem. End result is that it's running fine now on NG. Only issue is that the maximum power I'm getting out is 1400 watts, whereas I would get the target 1600 watts from propane and gasoline. I realize there is a derated output with NG, but there also is a slight derating with propane, which put out 1600 watts without a problem.

The problems I fixed were:

I shortened the hoses from the KN regulator to the carburetor by about 6 or so inches.

I noticed a slight kink in the bend of the smaller hose that leads to the carburetor and repositioned it.

The fitting that adapts from the larger hose to the smaller was not thread sealed, so I fixed that.

I also observed that this fitting is also a restriction for the flow of fuel, with only about a 1/8" diameter hole. It adapts to the smaller 5/16" hose leading to the carb.

papa · October 2013

Re: Generator on Propane/NG Issue

Good to hear.

northerner wrote: »

End result is that it's running fine now on NG.

Is it now sensitive to both lean & rich mixture adjustments with both gasious fuels?

northerner wrote: »

I shortened the hoses from the KN regulator to the carburetor by about 6 or so inches.

I asked about this in my first post. This is undoubtedly, the most common mistake made when converting. Ideally, the demand regulator should be mounted directly to the carburetor w/minimum pumbing - but I understand that isn't always possible.

northerner · October 2013

Re: Generator on Propane/NG Issue

papa wrote: »

Good to hear.

Is it now sensitive to both lean & rich mixture adjustments with both gasious fuels?

I asked about this in my first post. This is undoubtedly, the most common mistake made when converting. Ideally, the demand regulator should be mounted directly to the carburetor w/minimum pumbing - but I understand that isn't always possible.

It doesn't appear to be sensitive with the mixture adjustment on NG. I set it up with the mixture turned out 1/2 turn at a time till the genset reached an output level of 1400 watts. Turning the load block out further (nearly all the way out) had little effect. I'm no longer operating on propane and unnecessary now that I'm on NG

The hose is still over 2 feet long and is done up exactly according to instructions given by the supplier of the kit (CMD). I was able to take out about 6" of extra length in the hose, not a huge difference, but I'm sure does help. I was really surprised at the small diameter of the brass fitting which adapts the larger hose down to the smaller one (about 1/8" in diameter). That alone is quite a restriction, given that your piping in the NG through a 1/2" line that is relatively short.

northerner · November 2013

Re: Generator on Propane/NG Issue

I'm having another minor issue with the generator charging through my Outback inverter. I notice that the loads listed on the mate are noticeably higher when charging than when on the inverter. For example a typical load of 100 watts running on the inverter, will show up as 300 or so watts on the mate when the generator is running and charging the batteries. I noticed this ever since switching to natural gas. I know that the mate doesn't display the power consumption very accurately, but is usually within 100 watts or so. Any ideas?

NorthGuy · November 2013

Re: Generator on Propane/NG Issue

northerner wrote: »

I'm having another minor issue with the generator charging through my Outback inverter. I notice that the loads listed on the mate are noticeably higher when charging than when on the inverter. For example a typical load of 100 watts running on the inverter, will show up as 300 or so watts on the mate when the generator is running and charging the batteries. I noticed this ever since switching to natural gas. I know that the mate doesn't display the power consumption very accurately, but is usually within 100 watts or so. Any ideas?

I think it's simply not precise measurements. My XW also has very poor accuracy. I've got an impression that not all the numbers are actually measured, but some are calculated. Reading through the forum, it looks like all these inverters were designed by the same people. Apparently, the accuracy of measurements wasn't on their priority list.

That's just a number and it shouldn't affect functionality.

northerner · November 2013

Re: Generator on Propane/NG Issue

NorthGuy wrote: »

I think it's simply not precise measurements. My XW also has very poor accuracy. I've got an impression that not all the numbers are actually measured, but some are calculated. Reading through the forum, it looks like all these inverters were designed by the same people. Apparently, the accuracy of measurements wasn't on their priority list.

That's just a number and it shouldn't affect functionality.

Thanks for the response! That's what I was thinking, but the error in measurement is more significant than usual. So when I'm reading 1400 watts in from the generator and 1000 watts of charging + 400 watts load when the actual load is around 100 (+) watts, I would actually be charging at 1300 (-) watts rather than the indicated 1000 watts? I should check this out with a meter.

Blackcherry04 · November 2013

Re: Generator on Propane/NG Issue

I agree with North Guy, it's just a number. Mine on the Mate dance all over the place and they change often, what you see one minute may not what you see in 10 Minutes. Part of it may be the sampling and part is that the charger output / input seems to be a dampened number.

Generator on Propane/NG Issue

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