jmhooten Posted December 19, 2012 Share Posted December 19, 2012 Ok my 92' dolphin 900 has the factory Generator and I was told it "used to run but won't" so I haven't even bothered trying it knowing it needs at least fresh oil and a new plug. So, if you've dealt with a 20 year old generator that's sat unused for a couple years at least, can you give me a primer on what other items I might want to look at? Carb rebuild? Etc. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
zero Posted December 19, 2012 Share Posted December 19, 2012 Ok my 92' dolphin 900 has the factory Generator and I was told it "used to run but won't" so I haven't even bothered trying it knowing it needs at least fresh oil and a new plug. So, if you've dealt with a 20 year old generator that's sat unused for a couple years at least, can you give me a primer on what other items I might want to look at? Carb rebuild? Etc. Thanks in advance! Gasoline engine or propane? If gasoline, the "no start in years" problem is usually gasoline turned to varnish. If it was only run on propane, that won't be an issue. Propane and diesel can sit for 10 years with no issues. Whatever it is - you check the three basics. Spark, fuel, and compression. If it ran when last stored and was inside - the fuel and spark should be the only issues. To check spark - hook a plug wire to a spark plug with the opened up or even broken off. A spark plug with the ground electrode broken off makes a perfect test plug. Make sure it's touching against ground and when cranking - you should see a blue spark. With fuel? If gasoline it's easy to check. If propane it gets much more complicated. Which do you have? If the engine was exposed to weather - the exhaust valves can stick open resulting in no compression. I've had to pull the heads off of many and free them back up. Besides the engine running or not - another issue after sitting for a long time is the loss of residual magnetism and no power output due to no initial electrical excitement. Several ways to easily recharge it IF that ends up being a problem. If the engine runs but you get no AC - it needs a recharge. Quote Link to comment Share on other sites More sharing options...
dolphindriver Posted December 19, 2012 Share Posted December 19, 2012 Your carberator is probably all varnished up unless the previous owner drained all the gas out of it prior to not running it. These carbs are tricky - they are not designed to be rebuilt - they want you to buy a whole new carberator. The small passageways can be very difficult to get the varnish out of. It is possible to rebuild I think - but I don't know where you would get the carberator kit from. Gas Onan's are designed to be run/exercised every month. Quote Link to comment Share on other sites More sharing options...
zero Posted December 19, 2012 Share Posted December 19, 2012 Finding carb kits is usually not a problem with the older Onans. Can't say how it goes with the newest. Just about any carb of any make has small circuits that can plug and be difficult to clean if gas has turned to varnish. I've fixed many chainsaws with smaller circuits then the Onan's use. Most I've had to work on could be fixed. The problem with specialty stuff like Cummins/Onan is they jack the prices way up since it's an RV market. A carb kit that ought to cost $15 can sometimes cost $75 if you buy it from Onan. Sometimes you can pull apart, clean, and put back together with few or no new parts. All depends what's wrong with it. If a carb sat full of gas for 20 years and it's turned to rock-hard varnish - then a good fix will be near impossible. Quote Link to comment Share on other sites More sharing options...
jmhooten Posted December 19, 2012 Author Share Posted December 19, 2012 One question on the gas note, when I pulled the gen there was no fuel in the line. That could mean good things as far as varnishing... but does the gen "suck" fuel or should there have been some pressure/fuel in the line? This is a gas Onan that gets its fuel from the main tank on the RV. Quote Link to comment Share on other sites More sharing options...
zero Posted December 19, 2012 Share Posted December 19, 2012 One question on the gas note, when I pulled the gen there was no fuel in the line. That could mean good things as far as varnishing... but does the gen "suck" fuel or should there have been some pressure/fuel in the line? This is a gas Onan that gets its fuel from the main tank on the RV. I don't know what model # Onan you've got. All the ones I've worked on in RVs had their own electric fuel pumps on the engine. Some REAL old ones have mechanical or vacuum operated fuel pumps. What you've probably got is a model with a push button start. When you push that button it is supposed to send 12 volts to the fuel pump, the electric choke, choke heater, and with some - an added fuel shut-off solenoid. Fuel will only pump when you hold the push button IN. Once running and engine senses charge voltage and sends a signal to keep the fuel pump working. Again - to be more specific I'd need to know your model #. Quote Link to comment Share on other sites More sharing options...
fred heath Posted December 20, 2012 Share Posted December 20, 2012 My Onan genset is a gas powered 2800 watt. Model 28KVA. Made in 1988. Having spent the last 6 months working on it before I got it running right, I have a good knowledge of the internal workings. if yours is a gas powered microlite, let me know, I'll give you as much help as I can. Fred Quote Link to comment Share on other sites More sharing options...
Maineah Posted December 21, 2012 Share Posted December 21, 2012 That is a very popular generator used also as a camp generator. Onan is owned by Cummings diesel and they will have any part you could ever need for it. The only thing that I would not buy from them is electronic parts. All of the normal service parts are very reasonable filters and stuff like that. Onan is probably the best industrial generator out there. Quote Link to comment Share on other sites More sharing options...
Vanman Posted December 21, 2012 Share Posted December 21, 2012 After getting ours to run well, I thought, I put a digital meter on the acc 120vc outlet. WOW 140 vac light load , microwave takes it down to 128v, air conditioner and microwave take it down to 119vac. You can hear the gas engine load down with the increasing demand, but after a slight dip the speed remains constant. I am assuming the freq is 60 cps, but am no longer trusting this, as I do not have a meter that will measure this. The manual I have (from this site) says you need a resistor bank load for testing and adjustment as well as the proper electric meters, Time for a professional I guess. vanman Quote Link to comment Share on other sites More sharing options...
5Toyota Posted December 21, 2012 Share Posted December 21, 2012 vanman ever see one of the old resister banks made out of a row of incandecent light bulbs in parilew losen or thighten bulbs to change load. WHAT IS YOUR R P M I THINK IT HAS TOO BE 3600 to make 120 volt at 60 cycles. as the load increses the governer opens the throtle more to keep same speed Quote Link to comment Share on other sites More sharing options...
Maineah Posted December 21, 2012 Share Posted December 21, 2012 Yes it needs to be at 3600 for 60 cycles with out a doubt the best method is with a frequency meter but you can adjust it to a reasonable voltage there is a large screw that you can see near the top of the generator turn some thing on, a light load maybe a couple 60 watt lamps and turn the large screw until you get a reasonable voltage once that is set it should speed up with a load but the voltage should either take a slight dip or stay the same as you load it. If it is all ready running too fast the voltage will be high with a light load and it can't downward adjust. Quote Link to comment Share on other sites More sharing options...
zero Posted December 21, 2012 Share Posted December 21, 2012 After getting ours to run well, I thought, I put a digital meter on the acc 120vc outlet. WOW 140 vac light load , It doesn't sound that far off. First I'd double-check your voltmeter. Stick it in a grid socket and see if it reads 118-120 VAC. Many RV generators have been turned up a bit so they can run battery chargers better. If you feel your voltmeter is reasonably accurate, just turn the RPM down a bit. With an AC generator, the fixed max RPMs determines the voltage and also determines the Hertz cycles. You cannot adjust for either separately. It's one or the other. If the Hertz cycle is off, it won't affect much unless a clock is involved. Clocks will run fast or slow with the wrong cycles per second. Small RV gensets are known for making low voltage - thus the reason why it may have been turned up. 120 VAC from the grid is 170 volts that swing back forth with the cycles. The 120 VAC reading is an average and different type of meter read that differently. If I was real concerned, I'd only trust a RMS (Root Mean Square) volt meter. With little hand-held units, RMS based ones usually cost at least $60. Battery chargers like used to charge car and RV batteries, screw guns, cell phones,etc. do not work well with low voltage from AC gensets. That's because many models only work off the 160-170 volt peaks in typical 120 VAC power. Many small gensets only peak at 150 and thusly do not work well with certain chargers. This is why they are sometimes turned up. Like I said, RPM is the factor with AC generators. NOT a factor with inverter generators since inverter generators make DC and invert into AC - so they make a simulation of 60 cycles at any engine speed. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.