Replace Onan 4.0 BGE F electric fuel pump?

[tiinytina]

The fuel pump on our 4.0 BGE F series Emerald One seems to work "sometimes" but not always. The genny runs fine one time then next time fuel filter empty... let it gravity feed full, next run starts runs fine. Did a full tune up on the genny this summer, points, plugs, wires, filters, oil, control board rewired etc. 

Do these pumps fail sporadically before they fail entirely or do they just go.... opinion at Onan is that they don't usually but "can"...

Of course with my mechanic standing next to me it started and ran perfectly... but yesterday fuel filter was empty and it wouldn't start, and today prior to his arrival it started but wouldn't stay operating... then he does same thing I was doing and poof... ran fine and under load...

Checked tube from tank (main gas tank is full of fresh fuel). 

thanks!
Tina

[RV Mech Tech]

Tina - two possibilities here - if the pump is operating o.k. then check for the following - a) vehicle fuel tank cap not venting properly or  beginning to fail- your fuel delivery system is a 'closed system' so that no gas fumes can escape into the atmosphere and the gas cap must allow air to enter when the vehicle engine or the generator is running , but not allow any fumes from the tank to escape into the atmosphere - if the cap does not allow air to enter then a vacum will be created in the tank and  under certain conditions can starve the generator and possibly the vehicle engine-  I have seen three brand new class A motorhomes with this problem direct from the factory !  next time the gen quits try removing the gas cap and see what happens- again this is only a possibility - b) on some of the older vehicles the generator fuel pick up hose had a small filter on the end of it in the tank ( same as snowmobile or ATV tanks)  - if there is any debris in the tank (rust, contamination from bad gas etc.)  then that small filter may be plugging up - when the generator fuel pump is running that debris may collect around the filter and eventually plug it and when the genset stops the debris  will fall away from the filter allowing the gen to pull fuel again - this may explain why the gen will run some times and then starve for fuel other times - when the filter at the generator is empty try disconnecting the fuel line and injecting low pressure air backwards into the line - if the fuel flows freely after that then that may indicate there is something in the tank - I would also check the vehicle engine fuel filter as well - you can also check the fuel pump flow  by disconnecting the line to the carb, putting it into a glass jar and then cranking the generator to see the amount of fuel that comes out (have someone at the start button to shut it down quickly)  c) check to make sure that the 12 V to the pump is not cutting out as well - you may still have a loose connection  somewhere - there could also be a loose connection inside the pump as well - I would hook a test light ( or multimeter) in series with the fuel pump 12 V wire and watch to see if it cuts out - if so then you may have a control board problem - again these are only possibilities - hope this helps. 

[tiinytina]

Gas cap is new this spring... bought a locking one as where I park it at my folks the "renters" were starting to steal stuff and she holds 80 gallons... Engine in RV is running smooth... the connection off the fuel pump are all steel lines so removing to check pump is prohibitive without removing pump from genny but I can check... will check voltage as well.. problem is that the problem is sporadic... I had tried for 5-10 min to crank the genny over the other day prior to my friend showing up, so RV did not move,, he does same as I did and poof she ran fine... I was about to disconnect the fuel intake, fill a jar, and run the genny intake into the jar to see if fuel was being pumped out but didn't get that far... I believe on our chassis that the dip tube for the genny sits above the bottom of the tank so that you don't use up all your gas accidentally and get stranded... Think I remember seeing a picture of it in the manual.  I put a clear fuel filter on and from the looks the filter is still spotless.

Question. Can the control board be removed and tested? The Onan place is just up the road from me so even taking the whole rig there to test is not out of the question. 

I bought the newer version of Stabil (its blue) for treating heavy use engines (marine etc) especially older ones that can't deal well with the new ethanol gas formulations. going to run that through this weekend to make sure its mixed in etc... supposed to prevent gas oxidation as well as varnish build up in carb.

will let you know.. may just err on the side of old genny and OEM parts becoming hard to find and buy the fuel pump... yes I know I can buy a generic one for lots less but because the genny sits under the RV over the road bolted to a welded frame the OEM filter fits into a holder and I don't want to have to play with rerouting lines etc...

thanks!
Tina

[RV Mech Tech]

Yes the control board can be tested outside of the gen- the Onan manual has the procedure in the back of it for checking all the control board circuits or you can take it to the dealer- you may also have a temp problem with the board as temperature and age can cause a problem one time and not the next with the soldered connections- seen that several times in the past-  one of the biggest problem areas are between the board terminals and the wiring harness connections so check those and also for any visible signs of burning or corrosion on the board- if you want to get a manual for the BGE 'F' series the part number is  # 965-0528 - this is the  manual that I suggested to fgutie35 as he has the same gen as you do and covers both the point and electronic ignition series - the manual comes with all the updated bulletins (yellow pages in the back) and you can troubleshoot and check the board with a multimeter  to make sure that the board is or is not defective before you spend the big $$$

[fgutie35]

Ohh Ohh Ohh, finally my chance to help someone here. 
Ok, well I had the same problem that tina has when I first got my MH. It was hard to diagnose becuase like tina mentioned, sometimes it would work fine and sometime it would not. the weird thing was that the fuel pump will be runnig on ALL ocasions, I even removed the connector and powered the pump with an external battery at the same time I was cranking the engine, but no gas. Finally decided to do surgery on the pump and dissasembled it. It turned out that the rubber diaphram was all torn, and it seems that it was tearing gradually therefore sometimes it would siphon and sometimes it would not, depending on the poisition of the torn diaphram. Well I went to buy one for the Emerald Plus because at the time, I could not find the OEM locally nor online. By the way the one I got was cheaper $60 compared to the OEM $115. I just had to do some modifications to the fuel lines to make it work.

[tiinytina]

my "intuition" is saying fuel pump... and OEM right now is $102 and there are only 2 in the warehouse and 1 at my dealer now and got told that they are phasing out parts... soooo. there is no place to mount an aftermarket one on ours... it sits bare on a rack behind the drivers side front tire above the road... Oem twists into place, all metal lines running from it... soooo... I'm pressing the EASY button on this and buying the replacement Tuesday....

Tina