Onan HGJAB (5500) won't start

After leaving 5 months in storage, generator tries to start but stops when button is released.  If I hold for 30 secs, it surges or hunts moving the governor back and forth.  It gives me a code 0f 4 blinks(Overcrank).  Removed carb and bowl and found float and needle valve working freely.  Then, left air filter off, tightened 2 nuts holding carb, and I filled the bowl with sea foam 2 ? 3 times with the same result.  Stops when I release the start button.  Disconnected fuel line and found fuel pump working ok and installed new fuel filter.

After several attempts, coach battery drained to about 6 volts.  Then cranked the MH engine to try some more. 

Decided to follow Flight systems guide for troubleshooting.
http://www.flightsystems.com/pdf/onan-rv-troubleshooing-guide.pdf
which says to check if the generator is producing ac voltage at the circuit breaker or if the oil pressure signal is not present, unit won't start.  Haven't done that yet.

So decided to order new carb from Amazon and install to see if that corrects the surging ($250).  Waiting to go further with new carb.  Also have parts to change oil and filter, spark plugs, and air filter.

Any helpful comments would be appreciated.

If i had to guess i am sure the new carb will fix it. my old rv's geny went thru two carbs one with me one with the previous owner. when i replaced it i added this valve to shut fuel and let it run dry running to keep from gumming. In Line Fuel Shut Off Valve fit's 1/4" fuel line Briggs
http://www.amazon.com/Replacement-Briggs-Stratton-Cut-Off-494768/dp/B002HPX2V0

Not so sure it will run on the seafoam by it self. I've never used the stuff but from what I've heard it is supposed to be mixed with gas. I believe I would  have did the trouble shooting before ordering a new carb. Try removing the air cleaner and spray some wd40 while cranking it over, and see if it will run. just spray in short burst not constant. If it will start and run with spraying the wd40 then it's a fuel problem, if it won't you need to look further.

Received new carb today.  Ordered B&S fuel shut off.  Do you install before the fuel filter going into the carb?  Does this eliminate the need to put conditioner in the gas?

Sea Foam idea came from this video.
https://www.youtube.com/watch?v=CLLI359w2RM

Yes before the filter that goes to the carb so it is there in front easy to open/close. the fuel conditioner is probably needed to keep the fuel fresh and free of moisture. this valve is to keep the carb dry when in storage and from not gumming or varnashing itself.

cfuller201 said:

Received new carb today.  Ordered B&S fuel shut off.  Do you install before the fuel filter going into the carb?  Does this eliminate the need to put conditioner in the gas?

Sea Foam idea came from this video.
https://www.youtube.com/watch?v=CLLI359w2RM

Click to expand...

Installed new carb and tried new control board.  No success

Onan 5.5HgJAB-901A tries to start but stops when button is released

After leaving 5 months in storage, generator tries to start but stops when button is released.  If I hold for 30 secs, it surges or hunts moving the governor back and forth.  It gives me a code 0f 4 blinks(Overcrank).   913 hours on timer.  Have changed oil and filter, air filter, fuel filter, spark plugs, new carburetor, tested with a replacement 300-5374 control board.  Put sta-bil in gas tank.

Met with Mobile repair professional and he gave up after making the following checks:
- Tested with replacement control board (may still be the problem?)
- While holding start switch on, no 120 v ac at the source side of CB1 breaker.
- Cleaned brushes and slip rings with emery  cloth
- doesn't come up to needed rpm
- Choke plate doesn't advance past 47 degrees
- fuel pump filling bowl ok
- oil pressure signal is present.
- After trying a few times the status light went out ,  Also the coach battery drained and required the engine to be running to get 12 volts
- Have not tried to adjust valve lash

So my guess is trouble might be with the fuel system
- automatic choke settings
- governor adjustments
- don't know if voltage regulator on control board is working.  Probably not getting that far in the start up cycle
- electric choke heater not working as it stays at 47 degrees.

Looking for DIY next steps before taking to cummins Onan dealer in south Atlanta.

I am having a non start issue with mine same Genset.I have noticed my butterflys are not closed all the way and its mod 40s here so according to the book anytime weather is under 70*F it should be closed all the way.Mine will eventually start but I usually have to pull down on the govener lever then it will usually stay running after a couple attempts once it fires.  I will be playing with the electric choke on mine and possibly replacing it.... Just looked at mine again today BTW

Hear is a SWAG have you checked the oil level? also sometimes the low oil pressure switch will stick and no show oil pressure and it won't stay running when you stop pressing the start button.
Bill

WILDEBILL308 said:

Hear is a SWAG have you checked the oil level? also sometimes the low oil pressure switch will stick and no show oil pressure and it won't stay running when you stop pressing the start button.
Bill

Click to expand...

Also check the main fuel tank level....usually these generators are intended NOT to run if the gas tank is below a certain level (1/4 tank +-). Also, my generator didn't run, and one of the reasons was a SPLIT rubber fuel hose between the gas tank and the genset. The fuel tank had to be lowered and a new rubber hose installed in order to make it right. Just some thoughts.

- oil level is good.  Tech verified this and disconnected switch on new carb
- gas tank is full, now loaded with sta-bil.

Now status light quit working.  Pin j1-23  on control board should light this up.  Does this mean the control board is bad??

Since the governor surges when cranking, I think the fuel area adjustments are off.

I was under the impression that if the unit stops after the start switch is released indicated no generator output.  In reply #5 you noted no 120V, I am presuming this is indicating zero volt output from gen?

Fred

So it does not start or attempt too or start stumble or anything? do you have the house breakers (110) off to eliminate that side of things till you get it running? plugs didn't foul or did the old ones come out soaked? checked for spark?
fuel in tank is not too old weak?
Did you see these troubleshooting videos? (ignore the 4C stuff doesnt exist anymore)
https://www.youtube.com/watch?v=CLLI359w2RM
https://www.youtube.com/watch?v=ndyWd-R8Psk

Were the slip rings really dirty? High existence will burn a voltage regulator out. Does it run when start switch is held then stop when  released? Can you ohm the slip rings? If nothing what take a pair of needle nose and snap the brushes making sure they are moving freely. I have 3 JAB's spec A in shop right now with same problem right now. Sure sounds like a control bd to me, are you sure the one you tried was a good bd? You can bypass the jabs so you can make it run to diagnose further but make sure the brushes are free first. If I remember it's pres the start button 4 times fast if that doesn't bypass its the stop button 4 times fast will put it in bypass mode. If it runs with either or wd sprayed into carb it's a fuel issue like someone said earlier. Fuel, spark, compression, but I'll bet bad bd

Resistance not existence sorry replying from an I phone

Another note are you sure the rotor is turning dumb to ask but had one not run do to broken belt on bottom.

What we know so far:
- replaced carburetor
- cranks but produces no 120 v ac at the breakers.  Cranking with no load on genny.
- Didn't start with replacement control board from Tech (may still be the problem?)
- Cleaned brushes and slip rings with emery cloth
- doesn't come up to needed rpm and frequency.
- Produces a fault code of 32 ? low cranking speed sense.  status light ok.
- Governor swings back and forth when attempting to start
- Choke plate doesn't advance past 47 degrees when cranking.  Disconnected 2 spade lugs from choke heater terminals and applied +12v and ground to choke heater terminals and in 6 minutes choke plate opened fully
- When I held the start button, 12 volts did not appear at the choke heater terminals from the control board
- fuel pump filling bowl ok
- Put on new fuel filter in front of fuel pump
- oil pressure signal is present.

Next steps:
-  Check field flash windings and quadrature windings
Disconnect P! to control board and measure ohms across the following pins to check field flash windings:
-  P1-1 to p1-10  It should read about 30 ohms
- P1-3 to p1-9.  It should read about 2.7 ohms
- p1-1 to ground.  It should read no continuity
- p1-3 to ground.  It should read no continuity

Disconnect leads T1 and T3 from the circuit breakers.  Locate leads T2 and T4 where they connect to the common grounding lug and remove them from the lug and separate them so they are not touching each other or ground.
- T1 to T2 should read about .3 ohms
- T3 to T4 should read about .3 ohms
- T1 to ground should read no continuity
- T3 to ground should read no continuity

If I give up, will go to cummins onan dealer in south Atlanta.

Answers to queries:
maddog:  Will check to see if rotor is turning.  Pushing start switch causes generator to crank but stops when released.  Unit surges while switch is held down.  I too suspect the control board but at $329 will make some additional tests.  Will ohm the slip rings.  Status light is working ok.  fault code 32.

Sam:  Will check spark plugs and install new ones.  Gas tank is full and I loaded 30 oz of stabil in the tank.  House breakers are off.  Plugged into AC and converter puts solid B+ at the generator inputs.  Before I replaced carb, tried the Youtube videos with Sea Foam.  No effect.

Fredbon:  When cranking  0 volts ac at the breakers.  See next steps.

Pcarollon:  Put +12volts on choke heater and it opened fully in 6 minutes.  While cranking measured 0 volts dc on choke heater terminals from the control board.

Possible causes:
1.  Bad control board, 300-5374
2.  Bad choke heater?

I Loosened the screws holding  the Choke heater in place I rotated  the Choke clockwise until it closed choke plate completely. When I did that the Generator fired right up and vacuum controller pulled plates open.I see in the service manual for Generator  there is an alignment mark but I didnt see it I am sure what I did probably isnt right but for now the Generator will start.I am going to see if I can get a new choke heater or get mine pulled apart to see if I can find the alignment mark. The choke plates should be closed in temperatures below 70* F according to the service manual

Need to replace brush block as they are below 7/16" minimum.
When I disconnected brush block leads, measured open back toward control board.

Possible causes
- replace brush block
- possible bad control board
- choke heater not working

Mad Dog you were right.  Coupler connected to flywheel was destroyed causing rotor not to turn.  Cumming spent an hour with GMan and nailed the problem.  Then I fixed it.  Required taking bottom off to get to flywheel.  Should have let them diagnose in the first place.  1 hour labor.

Final tally
replaced coupler
brushes replaced
stator replaced
slip rings cleaned

Used tripod and motorcycle jack
Found coupler destroyed.  $34
Ran like a top when replaced