genset bogs down under load

Zman yes you are correct I meant the rings where the brushes are. I have checked the hoses & they are good. I went ahead & pulled the carb apart & cleaned it with the Jets out. I will put it back together & see how it goes. The carb actually looked in really good shape other than some finish coming off the bottom of the float bowl. Which I know it doesn't take much. Thought I would replace the pump just to make sure.

The reason I changed the oil & filters was because it had not been serviced in 4 yrs. The guy gave me the motor home for free & I have been working a little at a time on it.

Where do I find the spark plugs on this unit zman? I figure they need replacing as well but couldnot find them unless they are in the back or under the cover which I can't get to it with out removing the gen.

I assume your Onan is a 7NHM Marquis, by the fuel pump part number you listed. And " cleaning the rings " you are talking about rotor slip rings where brushes ride. I have replaced the rotary type fuel pump with a piston or recip type pump numerous times. I mount it in tray at same location, just takes a little adaptation skill. Also trash the fuel shut off valve that rotary style uses. The newer specs from Onan use a setup similiar to this. As other poster states, be careful with pressure. You need to stay around 4-7 PSI with your pump selection. I often use a NAPA part no. 610-1050 with good results.
another thing to check is electronic governor actuator link rod (if you have a spec B and later model) This link rod, between governor actuator and carburetor often disengages at actuator lever, then
throttle will not fully open when you apply heavier loads. And as always, goes without saying, be extremely careful about gasoline and fittings and lines, checking for leaks etc.

I always, always, ALWAYS start with trying a bit of Marvel Mystery oil in the fuel and oil. It is an excellent cleaner, excellent tool to remove gunk out of carbs (yes even the teeny holes) and also helps lubricate and clean the upper cylinder & valves.

I've seen this stuff help engines that are seized function again. Basically, I see it as "top of the line transmission fluid" with super heavy cleaners.

I've used in go-karts, mowers, tractors, tillers, weed trimmers, vehicles, to remove rust, oil door hinges... The uses are vast. It also cleans fuel injection systems out and lubricates parts in fuel pumps.

B.B.Upch wrote:
So my onan 7000 marquis runs great until I try to put it under a load & then it bogs down. & eventually dies. It's bogs down to the point Tha it will not run my a/c but for just a second. I put new oil filter & oil (it is level) & new fuel & air filter on it. Tried cleaning the carb by running fuel & b12 in a gallon can thru it but still no change. Also cleaned the rings & still the same thing. I'm thinking of replacing the fuel pump next but it is the expensive 149-2267 on it now. Cam I replace it with the cheaper smaller one & mount it somewhere else? What else do you suggest?

How did you clean the "Rings". Never heard of that. WHY would you think changing the Oil/filters would fix this type problem? It will not. Bogging down is NOT a fuel starvation problem in the sense you think it is. You do not state how many hours, but have you changed the 2 spark plugs? This is not your problem but they probably need changing. Your problem is fuel starvation. It is a CARB problem. The jets in the Carb are clogged and the mixture and possibly the Governor system is out of adjustment. Running fuel system cleaner will NOT clear up the 16 jet holes. It only takes a few holes to be clogged or partially clogged to cause performance problems. The ONLY fix is to either take the carb apart and remove the jet and clean out manually or buy a new carb. Onan does NOT make a carb rebuild kit, but you can disassemble the bowl and access the jet and remove it and reuse the existing O ring and gasket. typical fuel pump problems will cause slight surging and then it just dies instead of bogging down. Doug

PS, aftermarket Fuel pumps LOOK the same but have a HIGHER psi rating than what Onan's require.

Don't be surprised if you have to remove and clean the carb. I am sure it is a fuel delivery problem so start at one end and go to the other.

It sounds like fuel starvation or a governor issue.

You don't say how old your rig is. It could be the rubber fuel line collapsing when needing a lot of flow. Pull fuel line at gen set and see how much volume your getting.

good luck
pointrow