Onan 6.5 nhe backfires, quits

I used to substitute a Mallory Ignition huge capacitor in place of the original. Actually this can still be done using a 450 volt rated electrolytic cap. But the uf rating has to be exactly the same as the original. I like 18-gauge cross-link wire for the power lead to the capacitor. I did this on several NHE's and the owners never had a complaint. But I forgot the capacitance value. Getting old :(

Actually the condenser was the problem if it were low fuel you would still have gotten spark, backfiring in absolutely an indication of bad condenser.

The coil was probably unnecessary but the flicker points condenser is a must to replace every few years. I look at things a little differently than some folks. Gasoline here is three dollars fifty cents a gallon. A gallon is not much fuel. A gallon saved is three-fifty, period. It saves money when engines do not burn as much fuel.

Glad you found the answer...

Mexicowanderer I think you were right. Installed the new condensor, replaced as much of the fuel line as I could (it seems to go into the tank from the top, inaccesaable), filled it with fuel and it started immediately. The tank had a little less than half a tank of fuel by the gauge, but I put in 40 gallons, so it was lower than that. A hundred dollars worth of parts later and I think I just didn't have enough fuel in the tank. Thanks to all.Learn from my mistake.

Well, the old coil was good, had my VOM on the wrong setting, got the new coil in and installed it, no joy. The condensor did not come in, so I used the old one, butI am going to a dealer in town tomorrow to pick one up. Would this keep it from starting? Also going to replace the gas line in case there is a break somewhere in the line. Any other suggestions? New voltage regulater, ignition module, board, plugs. Still only get on occasion a black, smoky backfire.

The manual I have specs 17.45k ohms to 19.8k ohms on the high voltage side, so it looks like you are correct.
You might try ASAP for that coil- not sure of the number, but they usually have good prices on Onan parts, and have good tech support.

Now not getting any spark. Swapped out the board to check, no improvement. Pulled the coil, 0 resistance between high voltage terminals. Looks like a new coil. Not sure why Onan's is so expensive as opposed to a regular coil, but, not much choice. Any opinions on my diagnosis?

With the ac off, the capacitor would not enter into the equation at all. Have you looked at the spark plug?

Would a bad start capacitor in the a/c system keep it from starting or running? Even with the breakers off? I went back over today to try out some carb. cleaner, it tried to start backfired a couple of times, then nothing. The engine turns over, but doesn't even try to start. So tired of this, we were to leave on a trip next week, but can't travel in the south without the gen, too hot.