HELP, Propane genset delemma

Hello fellas, I know this board is for old lightplant questions,but I'am stumped on a modern propane fueled Onan light plant, Need to talk to a knowledgeable propane engine guy with vacuum flow regulator knowledge. I don't want to violate the board rules on old iron only - -so please make contact via E-mail ( address above). Thanks again Harry for the great site. - - Gary

Gary, Your genset will be old someday, so I guess it qualifies to be posted here. I can't help at all with your problem, but a light plant question is very welcome here, at least by me. There are quite a few gas powered light plants around, and I'm sure your not the only guy who ever had a problem with one. I had a newer (50s) Onan gas unit, and still have a much older Kohler unit. The only thing I can tell you about them is they are hard to start. My old Wards Powerlite catalogue says gas, whether it is natural, propane or butane, is not recomended for manual start plants or when the ambient temprature is below 30. I have a friend who bought a propane powered forklift and always had trouble starting it in the cold weather, he eventually converted it to burn gasoline, but he didn't need to run it indoors.

Thanks Gus - - You are right, it is a very hard starting problem. After prolong cranking, It will finally start, a little shakey for about 15 seconds, then will run very good as long as i care to use it. But shutting down, then trying to restart - it is prolonged cranking again ,even though it was just shut off a short time ago,and is still hot or warm. Some one told me it looks like i may need to service the vacuum flow regulator. This is a vapor fueled unit,direct from the main storage tank. No liquid vaporizing devices used in this application. Is there a way to test the regulator for vacuum leaks ? Also a short blast of starting fluid in the air cleaner, and it takes off right away. Any ideas ?? Thanks for your interest. Gary

A couple questions come to mind, first, where are you gettting the vacuum reference from? The information I have on propane vapor fueled Onans shows a regulator similar to the regulator on a barbeque grill. My second question is how large is your propane tank? If the tank isn't sufficiently large, the tank itself may not be vaporizing sufficient gas. Have you checked the output pressure of the regulator you have? Is the inlet strainer onthe regulator clean? Are the spark plugs gapped for gaseous fuel(.018)

Hello Franz - -Thanks for your interest. First of all I have no books on this genset, so I'am not aware of the plumbing for the propane fuel supply accessories needed to run . Because of the impossable location of this unit, I'am not able to see the regulator or associated plumbing. This unit is installed in a motorhome with a 40 gallon propane fuel tank to run all accessories. I was told by another genset owner that there is a regulator that was triggerd by engine vacuum to supply fuel for start up and running. Also the plug gap has not been verified yet,as the unit was installed at the factory, and not serviced yet. The hour meter reads only 140 hours run time since new. The only way to get to service this unit is to unbolt it from the frame and lower it down and out from underneath the mtrhome. I'am trying to get as many leads on what I can do with out that undertaking. The mtrhome is presently in winter storage,and I can't check it until early April. I can't even tell you the model of genset until I pull it from storage. I'am not at all happy with the wear an tear on the starter,along with the amount of power pulled from the house battery to start it. The charging rate to recharge the battery is a losing battle. I'll try to order a repair manual when I get the model. At this time ,all i know is it is a 6.5 KW ,1800 RPM. The only items I can reach are the oil fill & drain plugs,oil filter, one spark plug,and the mounted ON/OFF switch. - -can't reach the air filter wing nut if so equipped ?

How old is your generator and is it a cast iron 2cly. oppose engine. If so it would be a cck series engine these were used in alot of motorhomes/campers in the 60s to 70s.

Sorry, I forgot to mention its a 1997 vintage.

It sounds like your motorhome generator is as difficult to get to for servicing as most late model cars are.

As for the appropriatness of your question, the solution to your problem will also probably apply to those with older propane fired engines as well, and as such is a worthwhile discussion.

I am not an expert on this subject, but if I remember correctly, there has to be some intake manifold vacuum available to cause the propane supply control valve to turn on. Until the propane supply control valve turns on, there is no propane gas available to fire the engine. The use of starter fluid to initially get the engine going is a good indicator that this could be the problem.

If the propane supply valve is adjusted incorrectly, one of two things can happen. Either you get no propane gas and the engine won't start, or the propane gas won't turn off all the way, and it will continue to leak out when the engine is shut off. This is a potential fire hazard. Once the engine has started, either by using starter fluid, or naturally, there is greater manifold vacuum available and the propane supply valve operates correctly. That is about as deep as I can go on the subject. Good luck!

Thanks for your comments Russ - - I read it the same way as you said. The sad thing is they built the motorhome around the generator. It is impossible to reach and trouble shoot the problem with out major work to fix a possible small problem such as a leaking vacuum hose or to adjust or replace a regulator. So far there is no evidence of a propane leak. Once started it runs great,and does not seem to use much fuel, so I think that the regulation is fairly good. When I find the model number,I,am going to see if the library has information on how to solve the hard starting. Thanks again for your input. Best regards Gary

Gary i found two sites that may be of help to you the frist is funroads.com they have manuals that you can look at without buying. They also have a link were you can ask a Onan tech questions. The second site is perr.com/onan.html this site gives general history and specs. Both of the sites have some pictures of the latest rv generators that may help you id your unit.

Joseph

Thanks for the site info Joseph, I book marked them both for future use. I see I can order manuals direct on the funroads site once I identify my unit. Thanks to all that offered help on this thread - -Best regards to all -Gary

[straubpower]

You will have much less trouble if you run the propane set on vapor.
You need to reduce the tank pressure to about 11" of water column at the mixer. Usually two regulators are used . The reg off tank is red. Which reduces tank psi to 6psi. The second stage reg reduces the 6psi to 11" of water column. This reg is usually light green but can be other colors. Just before mixer an Imp 53 (Impco) (1" line) is installed upside down with the spring removed. The Imp 53 (or other proper size) acts as valving device and a regulator. As the engine cranks a vacumn is created which lifts the IMP 53 valve off its seat which allows the proper amount of gas at 11" of water column to enter the mixer. There is a adjustment on the mixer to adjust volumne of gas. Always install an electric shutoff valve in line. Install components to manufactures specs and local code.
Adjust mixer adjustment to maximum manifold vacumn under load if you do not have proper test instruments.

[straubpower]

also on turbo propane sets you will always need balance line between secondary reg and mixer. Sometimes on non turbo too but seldom

[Jim Rankin]

Sounds like a leaky diaphragm or valve sticking shut kind of problem.

If the shutoff device is piloted by a small line from the carburetor, You may be able to test it if you can find the line leading to it. A mechanic's hand pump or just sucking on the end on the line disconnected from the carburetor will determine if a vacuum can be maintained. Best to shut off the gas at the tank FIRST!

If it is opened by the direct suction through the mixer (carburetor), Just have if overhauled, or substutute a good one to try.

Good luck,

Jim

[Raymond]

Does it have a choke? Most LP engines use negative pressure systems which are hard to start. Partly because the mechanical governors shut down wide open. When starting there isn,t enough vaccuum to cause immediate fuel flow. A properly set choke would make it start a lot faster and more dependably. I have also seen solenoids operated with the starter to open the fuel valve and increase the regulator pressure. If you can get to the air intake try choking it with your hand at different degrees while starting and maybe you can determine how much choke would fix it. We are all presuming there is not another problem like poor ignition. The only LP engines I have seen start instantly are the ones I fitted with ALGAS carburetors. They are positive pressure feed requiring 5 psi. but they take off instantly. A fuel shut-off is mandantory because the carburetor has no shutoff. I setup around 10 Ford 300 Cu. in. sixes with liquid feed driving pumps. They never hesitated, and picked up full load instantly on the coldest days. As a safety I never turn off the ignition, only the fuel. after it stops then turn it off. If a magneto; no need to turn off.