Generac quit en route.

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garyb1st

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This is the second time it's quit when driving.  The first time, I was able to restart after a few attempts.  That was maybe 75 hours ago.  This time, nothing.  Called the man who serviced it before we left and he wasn't much help.  Suggested a possible fuel leak.  We've put about 100 hours on the genny over the past two months.  In total the generator has 583 hours.  It's a Q5500G. 

Manual says, replace/service air filter every 25 hours.  Replace fuel filter every 100 hours.  I was thinking of changing the air filter but may not be able to find one for a day or two.  Service guy didn't think a dirty air filter would shut it down.  Didn't have any suggestions other than a possible leak in the fuel line.  I don't have any mechanical experience and don't want to make matters worse.  I have changed the air filter and spark plug on a lawn mower.  Beyond that, I have no experience with gas engines.  I've looked at the manual and it seems like the air and oil filters are easy changes.  Not sure about the fuel filter.  Any suggestions? 

       
 
My Onan 4K on my old 2000 Coachmen would not keep running when the coach was underway.  It would run all when stationary.  I have tried a bunch of things, but never got to the bottom of it, although I'm convinced it's a fuel delivery problem.  I have since quit using the motorhome so I've lost interest in pursuing it further - at least for now.
 
Lots of things it could be, but two you should think about before going further.  One, did it overheat?  They shut down when too hot - if the outside temp wasn't high, probably not an issue.  Two, most generators have the fuel pickup set so they won't run  when RV is below  1/4 tank.

My Generac also has a low oil pressure cut out to protect the engine.  Could be a failed switch.

After that, it's the old does it have spark, gas and air.

Hope I didn't offend by stating the obvious.  I've forgotten to check the obvious too many times and still have to remind myself to check the easy stuff first = E brake must be on for slide to work!
 
Well, mine sure isn't overheating as it will quit in the 1st mile of travel.  If I immediately stop, it will restart and run for as long as I sit still - MH engine running or not.  It doesn't seem to be anything caused by road vibration, etc.  It will happen on a rough road or a smooth straight road.  It has plenty of oil.  As for the oil presure cutoff switch (isn't it actually a temps sensor?), again, it only happenes while moving and variations in road surface seems not to matter.  Doesn't means it couldn't be the switch, but doubtful.  I'm convinced it is fuel delivery, maybe related to negative pressure in the gas tank, but as I said, I've quit worrying about it for now.
 
I would try draining the fuel bowl at a minimum could have some water in there causing this, or taking it off to clean it and the needle and seat assembly. If you are able to drain it do it onto a rag so it doesnt spill all over the motor.
the Oil cut off should be a low level sensor so make sure its full to its level
 
Q55G should have a fuel pump prime switch on it, lower switch to the right. Push and hold the prime switch and see how long it takes to build pressure. Those switches are made pretty cheap and fail quite often. I've replaced mine 2 times in 1150 hours, but I use them a lot, and keep a couple of extra. The prime switch is a mom/on on  switch. The mom part of the switch passes power direct to the fuel pump, if the switch doesn't run the pump the pump is bad or the switch is bad. My switch failed while I was running the gen at the track and I just ran a jumper wire to the pump, had to remove the jumper when I shut the gen down. Those switches only cost about $4.00 each and have a different part number.
 
garyb1st said:
This is the second time it's quit when driving.  The first time, I was able to restart after a few attempts.  That was maybe 75 hours ago.  This time, nothing.  Called the man who serviced it before we left and he wasn't much help.  Suggested a possible fuel leak.  We've put about 100 hours on the genny over the past two months.  In total the generator has 583 hours.  It's a Q5500G. 

Manual says, replace/service air filter every 25 hours.  Replace fuel filter every 100 hours.  I was thinking of changing the air filter but may not be able to find one for a day or two.  Service guy didn't think a dirty air filter would shut it down.  Didn't have any suggestions other than a possible leak in the fuel line.  I don't have any mechanical experience and don't want to make matters worse.  I have changed the air filter and spark plug on a lawn mower.  Beyond that, I have no experience with gas engines.  I've looked at the manual and it seems like the air and oil filters are easy changes.  Not sure about the fuel filter.  Any suggestions? 

       
Click to expand...
As I mentioned in my earlier post, I was considering possible negative pressure as the cause with my generator.  Your problem could be caused by that.  Make sure your gas cap breaths (vents) properly.  Driving down the road, the MH engine will draw fuel and could cause a negative pressure (vacuum) if clogged or restricted.  The MH engine's fuel pump may be able to overcome it, but the generator's fuel pump may not be strong enough.  After driving some distance, quickly stop and open the gas cap.  Listen for a sucking sound which would indicate negative pressure.  Or, just change the gas cap with a new one for your particular chassis to eliminate the possibility.
 
56safari said:
Lots of things it could be, but two you should think about before going further.  One, did it overheat?  They shut down when too hot - if the outside temp wasn't high, probably not an issue.  Two, most generators have the fuel pickup set so they won't run  when RV is below  1/4 tank.
  The outside temp was in the mid-80's.  Don't know if it overheated.  Fuel tank almost full so that shouldn't be problem.   

My Generac also has a low oil pressure cut out to protect the engine.  Could be a failed switch.
Click to expand...
  How do I determine that?   

After that, it's the old does it have spark, gas and air.
Click to expand...
  Plenty of gas.  Spark plugs changed 100 hours ago.  Not sure how to get to spark plugs.  One on either side of air filter.  Looks like two bolts holding a cover of some kind.  Are they beneath cover?     

Hope I didn't offend by stating the obvious.  I've forgotten to check the obvious too many times and still have to remind myself to check the easy stuff first = E brake must be on for slide to work!
Click to expand...
No offense taken.  Thanks for the help.
Click to expand...
 
If my lack of typing skills doesn't fail me, you can go to www.generator-parts.com/manuals/generac-rv/0e7225.pdf to get a manual with the trouble shooting chart.  Not exactly the same unit as yours, but pretty close.  The manual also shows the spark plug location much better than  I could describe it.  Section 6 shows the trouble shooting sequence for a no start and how to perform each check is detailed in the manual. 

Here's hoping its one of first test on the chart!
 
Sam! said:
I would try draining the fuel bowl at a minimum could have some water in there causing this, or taking it off to clean it and the needle and seat assembly. If you are able to drain it do it onto a rag so it doesnt spill all over the motor.
the Oil cut off should be a low level sensor so make sure its full to its level
Click to expand...

Thanks sam but I wouldn't know a fuel bowl from a cereal bowl. 
 
56safari said:
If my lack of typing skills doesn't fail me, you can go to www.generator-parts.com/manuals/generac-rv/0e7225.pdf to get a manual with the trouble shooting chart.  Not exactly the same unit as yours, but pretty close.  The manual also shows the spark plug location much better than  I could describe it.  Section 6 shows the trouble shooting sequence for a no start and how to perform each check is detailed in the manual. 

Here's hoping its one of first test on the chart!
Click to expand...

Thanks for the link.  Don't have skills to go beyond very basic. 
 
I am wondering if the generator is located in a spot where the motion of the vehicle might tend to create a vacuum in the generator area where it draws it combustion air from, thus starving it in a manner similar to running out of gas.
 
Generator location is in bay midway between axles on drivers side.  It performed flawlessly for the past two months.  During that time we used it almost every day we drove and added 100 hrs to the clock.  Dash air works but small coolant leak when operating causes me some concern.  I'll take care of the leak when we're back home. 

One of the trouble shooting suggestions in the manual is to check the oil level.  It has an auto shut off when the oil is too low.  It was about a 1/2 pint low.  I added that this morning and no change.  I'm going to remove the air filter, clean it and the foam backer.  If I can find the spark plugs, I'll clean the tips as well.  A bit of sandpaper has always helped on the lawn mower.  If that doesn't help, I'll probably need to bring it in.  The motorhome has been bouncing along for more than 4,000 miles and we have had some rough roads so maybe something electrical.  I read that a solder connection can some times break causing a no start situation.  News at eleven. 

 
 
Great to hear you got it fixed, I was going to suggest an oil change, In case it was causing warm weather low oil pressure shut down.
 
Did you check the oil level?? Most will shut down when it gets to low. Good Luck and hope you get her running.
 
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