Just started to de-winterizing the coach this week.. (Better late than never) Had to jump start the coach, but brought it home a total of 40 or so miles and all ran well. It's now on shore power. Ordered a new air filter, oil filter and plugs from onan and installed them today. I can't get the 6.5 to stay running. Fires - attempts to run and quits. runs for about 1.5 seconds and quits. Coach has a hair under a half tank of gas.. At what level does the onan quit drinking ?
Any ideas? It ran fine when put to sleep last year. Silly question - does it normally start fron the house or motor battery?

The genset starts from the house battery. Most will not run if the fuel tank is below 1/4.

It sounds like it may have a sticky choke - check to make sure it's closing.

Also recheck the oil level, as the level in the crankcase will lower as the oil pump picks up, and it could be tripping the low-oil shutdown switch.

Fuel starvation sounds like the culprit otherwise; other possibilities are a plugged fuel filter, a stuck carb float, or crud in the carburetor.

just diverting a little here...any idea why the generators are started off the house rather than the coach batteries? Seems to me that house batteries are the ones that are most likely to run down to the point of needing recharging with the generator yet must then be used to start a generator that is often at the other end of the motorhome with long lengths of cable to drop voltage even more? Also, does running the gen set also charge up most chasis batteries thru the converter as well as house bats? Just some questions that I've had for awhile.

quote:

Originally posted by beeoh:
any idea why the generators are started off the house rather than the coach batteries?

House and coach batteries are the same thing. I don't know why there isn't standard terminology here, as it can be confusing. Most MHs have two battery banks: One is called house or coach. The other is called chassis, truck or starting.

If you used the chassis battery to start the genset, you could end up with a dead chassis battery after a while, as the chassis battery would not be recharged.

quote:

Also, does running the gen set also charge up most chasis batteries thru the converter as well as house bats?

Nope. Isolators are diodes that allow current to flow only one way. You could install a paralleling switch to do that, but you would need a pretty long stay in the boondocks to need to charge your chassis battery, unless you are running it down with the radio or something. I have wired our dash radio/tape/CD player to run off the coach battery to avoid running down the chassis battery. Chassis batteries do not like to be run down. They are meant for a big load and then instant recharging. Exactly the opposite of coach batteries.

I don't like isolators or any other system that charges two different types of batteries in parallel. Or any system that charges batteries of differing states of discharge in parallel. I have never had them work very efficiently. As an example, the Delcotron is designed to put out a lot of current right after start up, then loaf. It uses a temp sensor to reduce its output as the engine warms up. This effect can also be seen if they carry a heavy load and the heat of creeping in slow traffic will further reduce its output. I let my alternator charge the starting battery, and the genset or solar does the coach batteries. Each charging system is optimized for its intended service, and each charging system is reading and responding to its own battery bank. Technical considerations aside, there is a certain symmetry and balance there that appeals to me. An Aristotelian "Golden Mean", if you please. All is well with the world, sort of a Pythagorean Musica Universalis.

I should add here that converters are all over the map in their ability to recharge the coach batteries. Some do a fine job and some are designed to do little more than run the 12 volt loads. My Barth had one of the latter. I have replaced it with a big three-stage "smart" charger/converter to assure that I don't use a lot of gas and make a lot of noise to recharge the batts.

My Onan fuel pump likes to stick if it has been sitting for a while. It is the green can (no surprise it's an Onan) in about the middle of my generator on the outboard side. As I recall there is a hose out on top and the fuel comes in on the side about half way up.

The bottom comes off with a 1/4 turn, a little of Bill H's Rust Buster is not a bad deal on the OUTSIDE before taking it apart. Look at the bottom, mine has tits and a slot that holds it together, push up and gently rotate to remove. Or maybe just rotate, take a look before you pull out the fourteen inch channel locks. After you open it up clean the filter you should find inside and shoot some lube of your choice up into the thing, lube means oil not the rust buster stuff. Reach up inside and GENTLY poke the pump up and down to move the lube around.

This gets things working on mine; I suppose the pump should be replaced but I suspect I will replace the pump enshala. Enshala translates "when god is willing", this time period comes well after Manana.

Timothy

Many thanks, timnlana for your response - I looked but didn't see the unit you described however I did see what looked like the bottom side of a carburator with a idle adjustment screw at the bottom, I twisted it a bit and the unit stayed running.... The writing on this can stated altitude adjustment.. I let it run about 20 minutes and measured the ac at the outside plug and was surprised to read about 150 VAC -- so I believe something is still screwy -- I have an appt on wed to take it to a authorized dealer for fixin unless you guys can enlighten me...

It's probably best to have it serviced - voltage depends on RPM. While neither the RPM adjustments nor the altitude adjustment are difficult, without the manual, it's guesswork. My SOB came with all the genset manuals, so when I had a problem with the governor hunting, it was relatively easy to fix.

I would suggest buying a Kill A Watt and some Red Line Fuel System Conditioner. Get it into the carburettor and try to run the thing so the cleaner can work. Once it stabilizes, use the kill a watt to check frequency. Adjust for 60 cycles with a load, a little higher unloaded.

There is probably an electric fuel pump somewhere. Make sure it is working well. I would connect a fuel pressure gage in the line to the carb. Cheap vacuum gages usually read fuel pressure. Could just need some persuading like Tim said. Is there a fuel filter there? Does it flow? Gummed up carbs and old cracked rubber fuel lines are the most common genset faults.

I regret that I haven't worked on an Onan for quite a while, so can't remember much. The PO of my last SOB was given a high figure for a carb overhaul, so he just bought a new one and put it on himself for less money.

Most of the Onans use a mechanical fuel pump. Both Hz and voltage go up with an increase in RPM. I used my microwave's clock to check Hz, and a VOM for voltage. I finally got both settled down to where they should be, but I had the manual and an after-market book.

thanks bill h for answering my questions...I do know a coach/house battery from a chassis bat but didn't word it right...just traced out the system on my Breakaway and all are as you described..

Ah I had this problem and found the fuel line sucking vacumm from fuel tank. Check your tank vent may or not be just a suggestion.

thanks for all the input.... I have a kill-a-watt on order and the service manual. The local cummins onan service center wants a small ransom to make it right. figured I'd try a few thing myself. It does have an electric fuel pump, and I've read somewhere that this beast take 4 qts of oil ?? Seems like a lot.. Oh well , guess I'll wait for the service guide.

Thanks again

I've been working on my 6.5kw Onan 1985 model NH. It has a Walbro carb that has been made obsolete because they will no longer sell parts for it. Onan has a replacement carb made by Nikki for $165. I think that Onan got tired of selling cheaper carb kits.

Any electric fuel pump will work. I put a new one on mine just for security. I also carry enough fuel hose so that I can use my genset pump to get home if the engine pump fails.

Another tactic to isolate fuel problems is to run a hose from the motor home electric pump to the genset carburettor. This eliminates the genset fuel pump, pickup and lines.

hi rusty, i have a 1977 J-series 6500watt onan. it had a similar problem. i trouble shot it with the manual to no avail. eliminated all the possibilities. brought it to the mechanic(very reputable). he determined it was the R-1 resistor. he replaced the R-1 resistor(part# ON-353-0060) and a capacitor(part# ON-312-0246). there are 11 years difference between our generators so i don't know if part #s would be same. hope it helps.