On my 91 Warrior I have a 4kw Onan Emerald Plus. Will not start. Turns over like a top, but will not run. Tested the fuel pump, and it sounded very sick so I replaced it. Also replaced control board, as the manual switch was rusted and it had some corroded traces. Still will not run. I have determined that the fuel pump does not run when I am turning it over. So I hooked 12v to it and primed the pump and fuel system, and tried starting again. It caught for about 1 second, but did not run any further, and I have not been able to repeat that small success. There is plenty of oil in the crank, and the unit looks very good (not that it really matters, but I thought I would add that in).
Can anyone point me in the right direction? What would stop the fuel pump from getting power?
Thanks,
Ian
1991 Winnebago Warrior 30eu
OLD RIG
2006 Chevy Uplander 3.5l
2005 Jayco Sport 165 18' 3500lbs loaded
Putnam WD w/800lb bars
Acar friction type sway control
Hoppy digital display brake control
BALANCED tires! (Please everyone, balance your tires!)
1996 Safari Serengity, 3126 Cat,Allison 6 speed, 38' DPNS, 2005 Honda Element,vip tow brake. doran tire sensors, Magellan750Nav,
and 1 good looking wife, and missy and Alex(died 11-03-06) and AJ, born 09-06-06 my carins.
FMCA # F374886
I have a half tank of gas, but just to take it out of the mix, I hooked clear vinyl tube up to the pump and into a gas can. This is how I know the pump does not run when starting, but does if I hotwire.
I have been to the Onan website and downloaded the manual and read thru the FAQ, no help.
I would disconnect the gas supply hose and get another short gas hose and put it in a gas can to see if it will pick up the fuel and run the genny. If it does then it is either a crack in the hose or like previous post make sure that there is at least 1/4 tank full of gas as the pickup in the gas tank is up a ways from the bottom so that you do not run your gas tank out of fuel. If it does not start and it is taking up gas in the line, then it is spark.. pull spark plug and ground it to the genny chasis, but be careful to make sure there is not any fumes that could ignite.. turn engine over and see if there is spark... i guess the best advice is if you don't feel comfortable, get someone who is (local mechanic).......
electric fuel pumps are usually pressure related, so if it feels negative pressure it kicks on, kinda like keeping the line charged when there is power applied. so still could be the pressure switch or control board or usually the ground to the control board is questionable...
Low oil pressure sensors are semi-famous for going bad. I think you can disconnect it temporarily to see if thats it. An Onan will crank until it has oil pressure then it starts. Bad sensor, no sparkee.
There are only 3 things that a gas engine needs to make a bang of some sort - compression, fuel and spark.
These are the things that you need to test for and the easiest way is to spin the engine on the starter for 30 secs and then pull a sparkplug.
If it's wet and smells of gas then there is either no compression or no spark
If it's dry then there is no fuel.
Connect the spark lead to the plug and ground the plug away from the sparkplug hole (or replace plug in the engine and use a spare plug) and spin the engine. If you get a healthy spark then that's good - a weak spark means ignition system problems.
Disconnect both pipes to the fuel pump - put a hose on the Input and drop it into a gas can - put a hose on the output and drop in a mason jar or some clear container. Switch on ignition - if fuel is pumped check/replace the hose between the pump and the carburettor. Or clean/dsimantle the carb and jets.
If no fuel is pumped, connect 12v across the pump to see if it operates - if it does then suspect the starter circuit/oil pressure switch. If not then replace fuel pump.
Usually warnings of gas, sparks, heat and personal safety apply.
RV Park Finder
Fulltimers
2002 Beaver Santiam 38DST + Banks + 99 Jeep GC
DH,DW,Jake and Indie
Thanks for the many replies, but I have already done most of what has been suggested, with the exception of the low oil pressure shut off. I don't have the service manual, so I don't know where it is located. Can someone give me an idea where to find it? Would this cause the pump not to run or just take the spark to ground?
I had the same problem about three years ago on my onan. I have a friend that is an onan tech. He said to replace the voltage regulator and my problem would be over. I did and not more problems. They are expensive but I found another brand on the internet for about 1/2 the onan price. Your old one will have a number stamped on it that will be needed to purchase the correct one.
For the best advice please post the full genset model/spec and serial number. That way we will know exactly what you have and can give you some meaningful advice without resorting to guessing and/or telling you something that doesn't apply to your machine.
Sounds like you are on the way to get it working.
First, unless you got an Onan electric fuel pump you may have run into grief right there. The Onan needs a low pressure pump and an automotive one, unless it is a low pressure model, will flood the engine.
Use a volt meter to see if the pump is getting voltage and if not, where you are loosing it. Some of them have a fuse for the fuel pump (see why we ask for the numbers?)
Let us know how it turns out or if we can help further.
By the way.......I've been working on Onan gensets for well over 20 years, have seen very few (less than 10) failed oil switches, ones that did not work. Most common failing of oil pressure switches is leaks. Further more, a failed switch will not keep it from starting, it'll just stop running when you turn loose the start switch.
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