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Car Forum / Driving, Maintenance, Tuning / RVs / September 2006Onan Generator Problem Marquis 7000
hello I have a onan 7000 marquis LP gas. ran great worked fine. had the RV in the shop for about three months, generator not working. cranks, fine, just does not start. lp gas is about full. so I have plenty of fuel. cannot seem to find the regulator on the unit. to check and see if LP is getting to the unit. any experts out there. the RV is a 1992 Allegro Diesel Pusher. are there any groups of generator lovers out there, like the chainsaw and plumbing groups. thanks > hello > I have a onan 7000 marquis LP gas. ran great worked fine. had the RV in [quoted text clipped - 9 lines] > > thanks First things first - it would help a LOT to know the full model and spec of your genset - should be something like 7NHMFA 26105C. If the genset came from Onan as an LP genset, it is what's known as a liquid withdrawal system - it draws LIQUID propane from the tank, and turns it into a vapor and regulates it at the genset. As such, it will have a separate shutoff valve at the tank since it is using a tube inside the tank to draw liquid from the bottom of the tank. Everything else on the coach - water heater, furnace, refrigerator - that runs on propane uses propane VAPOR, from a different valve located near the top of the tank that feeds to a propane regulator right next to it. So the easiest possibility is that the shop turned off both valves, and only the vapor one got turned back on.... On the factory LP model, liquid propane line from the tank connects to a propane filter and solenoid valve near the control box. A metal line connected to the solenoid valve goes under the shroud, wraps around the exhaust manifold (to pick up heat to help vaporization) and continues to the vaporizer/demand regulator, which is mounted -inside- the shroud in the back left corner. From there, a hose runs back to the carburetor. If you are sure that the LIQUID valve is on, and it still won't start, try removing the air filter and spraying some starting fluid down the carb throat while cranking. If that makes it at least try to run, then it -is- a fuel system problem. If it doesn't try to run on starting fluid, then the fuel system may be ok and the problem may be ignition or control related. I don't know of any usenet 'generator lover' groups - alt.energy.homepower is probably as close as you'll get, but they're not going to be a lot of help with an -rv- generator. Let me know what you've got, and I'll walk you thru troubleshooting as needed. Alan Thanks Alan, The model of the generator is ONAN MARQUIS 7000 LP GENERATOR 7NHMFA26105B S/N I910421620 From the little I have read, I believe the unit uses LP Vapor, I cannot find a second shutoff valve and crawled under the unit, and attempted to run down the line but the line goes up into the RV. I have not run down the line from the RV back down. at the front of the RV under the Onan, there is a pancake device that runs vertical. I believe this is the regulator. I can take a picture and post it to a group so you can see if this is correct. thank you for your help. I am on the road today, so it will be Monday before I am able to work on the Onan. Michael >> hello >> I have a onan 7000 marquis LP gas. ran great worked fine. had the RV in [quoted text clipped - 46 lines] > > Alan > Thanks Alan, > [quoted text clipped - 19 lines] > > Michael Ok - from your description (and the model/spec), what you have is a GASOLINE Marquis that has been converted to run on LP vapor. The vertical 'pancake' should be the demand regulator - it should have an electric solenoid valve on its input side which is fed from the main regulator at the tank, the output side (the fitting at the top) will have a hose running to an aluminum cylinder mounted between the carburetor and the air filter adapter. First - remove the air filter and spray some starting fluid down the throat while cranking the genset. If it tries to run, then it -is- a fuel system problem. If it is a fuel problem, check the wiring to the electric solenoid valve (should be spliced into genset wiring where the gasoline fuel pump normally sits in right rear corner of genset tray - visible looking up from underneath). On the demand regulator, there should be a diaphragm vent on the outer edge of the pancake at about the 5 oclock or 7 oclock position (one will be vent and one will be plugged - the vent will normally have a fitting and a small rubber hose). Make sure the vent hose/fitting isn't plugged with mud, insects, or ?? If the solenoid valve wiring and the regulator diaphragm vent check ok, there is a plugged test port on the side of the regulator body where the input line threads in. Make up some soapy water solution, remove the plug, and use the soap solution while someone is cranking the genset to see if you have LP at that point (Caution - if you do, you'll have propane vapor escaping, so no fire/flame/sparks anywhere close..). If you have LP at the test port, then the regulator is bad. If you DON'T have LP at the test port, then either the solenoid valve is not getting voltage, the solenoid valve is getting voltage but not opening, or the solenoid valve is getting voltage and opening but is not being supplied LP from the tank. Alan > > Thanks Alan, > > [quoted text clipped - 53 lines] > > Alan Let me be the first to applaud Alan for his excellent advise. It is people like him who make this NG worthwhile. Hank I see where ninebal310@aol.com contributed: >Let me be the first to applaud Alan for his excellent advise. It is >people like him who make this NG worthwhile. You're much too late to be the first. Alan is among the most consistently helpful and courteous contributors, and had received several well-deserved attaboys. Will Sill The Curmudgeon of Sill Hill > I see where ninebal310@aol.com contributed: > [quoted text clipped - 7 lines] > Will Sill > The Curmudgeon of Sill Hill Damn Will, do always read sh.t into everyones posts or just mine? Do I have to spell everything out for you? As if it matters, I was the FIRST to commend him in this thread on this subject. If I had meant anything different, I'd have started a new thread. Geeeeez......get alife and leave me alone. Hank <~~~thinks Will has a crush on me Thank you Alan, I just got in, and will try this set of test tomorrow morning. >> Thanks Alan, >> [quoted text clipped - 54 lines] > > Alan Thanks Alan, I took the approach, start with the simple things to diagnose first. sprayed a little starting fluid in the carb, tried to run. so I removed both the vent and non vented plugs on the regulator, the one with the hose, had a blockage of some type. blew it out with air, pipe dope threads, both back on, started and runs like before, many thanks, you saved me $180 bucks from Cummins just to take it to the shop and diagnose what was wrong. I am sure they would have found something they could fix as well, to justify the charge and to not make me look so dumb. if and when you ever get to san Antonio, let me know, I owe you a lunch, cocktail, coffee in my opinion. thanks again. for your step by step diagnose and help. >> Thanks Alan, >> [quoted text clipped - 54 lines] > > Alan > Thanks Alan, > [quoted text clipped - 22 lines] > > thanks again. for your step by step diagnose and help. Glad to hear you've got it working. Now for the explanation... Air being pulled into the carburetor goes through a venturi (that aluminum cylinder mounted between the carb and the air cleaner adapter) which creates a small pressure drop in the hose from the regulator. The small pressure difference between the output side of the diaphragm and the vented side of the diaphragm causes the diaphragm to move and open a valve which allows LP into the output side chamber. If the vent is plugged, the diaphragm can't move, and the valve doesn't open. For some reason, insects seem to love the trace of propane odor present in the area - they get into the vent, and then die. If enough of them do, the vent gets plugged. Around here, the main culprits are leaf-cutter bees and box elder bugs. As you may guess, NOT the first time I've seen this. Alan ... > For some reason, insects seem to love the > trace of propane odor present in the area - they get into the vent, and then [quoted text clipped - 3 lines] > > Alan Ain't it the truth. Twice in the last 3 yrs I've had to pull my forced-air heater out, partially disassemble to get access to the jet and pull it to remove the dead critters that are so small they can get in through tiny orifice, die and then plug the jet. Starting this yr, when the MH is put away for the season. All the vents for the heater are going to be sealed up. Mickey Beware: The shop may have exchanged some of your good generator parts for some of their bad leftover parts so that they could make some extra money. Look for fingerprints. NM > hello > I have a onan 7000 marquis LP gas. ran great worked fine. had the RV in [quoted text clipped - 9 lines] > > thanks |
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