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Topic: 4000 Onan Genset fuel pump replacement for 2001 Midbath. (Read 431 times) previous topic - next topic
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4000 Onan Genset fuel pump replacement for 2001 Midbath.
Unfortunately my Genset fuel pump went out. The way the cabinet for the mid bath has been constructed, the mounting bolts are hard to access. Has anyone with a mid bath, built around 2000, been confronted with this problem before and  has any suggestions? Or should I abandon this pump and relocate it and reroute the fuel lines?

Aad Rommelse
2001 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #1 –
The generator fuel pump can be replaced with typical hand tools (in an Onan 4000) by removing a few smaller parts (solenoid and control module).  It's easier when you know where the bolts are.  These videos will show you what you need to know:

Determining if you need a new fuel pump:
https://www.youtube.com/watch?v=U72Zmk0BF-o&ab_channel=RVwithTitoDIY

How to replace the fuel pump:
https://www.youtube.com/watch?v=gutZQAq5Trc&ab_channel=KATZFamilyadventures

Rich

2003 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #2 –
If anything like mine, the fuel line will be clamped with special type clamps that you will need to cut off and replace.
Greg & Victoria
2017 Mid-Bath  “Nocona” towing a manual 2015 Forester
Previously a 1985 TK
SKP #61264
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #3 –
Do you have the older Onan Emerald or the Onan MicroQuiet?  I seem to remember that the MicroQuiet was used beginning with the 2002 LDs.

Art
Art and Barbara
Settled in Atterdag Village of Solvang
2015-2022 fulltime in a 2016 Tiffin Allegro Bus 37AP
2002-2015 2002 LD MB
Art's blog
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #4 –
Thanks Rich for your response. However, the Genset that Lazy Daze installed in our unit is the 4000 Emerald Plus, or Model BGE, The fuel pump has been mounted on the right, lower side of the Genset. The cabinet access door is just not wide enough to reach it. Even replacing the air cleaner is hard to access for filter replacement.  Even through the openings in the right hand hanger plate the fuel pump bolts are almost impossible to reach.
I was hoping that someone else with the same unit in the mid bath of that vintage had faced this problem.

Aad
2001 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #5 –
Ours is a 94 mid bath and the generator is mounted directly behind the front passenger seat. The compartment door opens enough to access the right side. When I changed our pump I had enough room to access the mount bolt with one hand. Once that was loose and the gas line disconnected from the carb, life was better. The inlet had a rubber hose connection and with the mount bolt loose this connection was easier. The whole thing was doable just not easy, make sure your fuel pump is bad first and not the hoses off the gas tank.

Jon
1994 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #6 –
Jons and others,
Fortunately the caution for the fuel line from the tank to the generator made me look into my problem a little deeper. My fuel gauge on the dash showed me that the tank was well over half full. (5/8). That is the reason I did not consider my fuel supply to be the problem. However, upon disconnecting the fuel line on the supply side of the pump, I found no flow of gas. Upon topping off the gas, the generator started up normal again. Knowing now that I have to watch this in the future I am happy that I did not have to get my knuckles bloody to change the pump.
Not being familiar with the inside of a E450 motor home tank I have a question. A few years ago I had my tank dropped for a fuel pump replacement by a shop. Could it be that at that time the fuel pick up fur the generator could have been damaged or bend?
Or is my dash fuel gauge a little off? Just curious

Aad
2001 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #7 –
Did the shop that replaced your fuel pump happen to replace the infamous deteriorating short section of fuel hose attached to the  generator fuel pickup?  It's not something they normally would do unless someone told them to or they noticed that the hose was in poor condition?

This picture shows the short section of fuel hose that commonly fails (Thanks LarryW!):
Fuel pump | lw5315us | Flickr

The symptom you describe (no fuel when the tank fuel level is lower, fuel when it's close to full) can be caused by a crack in the fuel line.  Commonly caused by the problematic fuel hose section, I've also seen a case where mice chewed small holes in the plastic portion of the generator fuel hose.  I diagnosed this by pulling the hose off at the pump end, pushing air into the hose, and listening for leaks.  You can also pull suction slowly and monitor for air intake.  A shop could use smoke. 

I doubt the fuel pickup was bent when the fuel pump was replaced.  Another LarryW picture shows that it wouldn't be easily bumped (This picture shows the pump upside down and the generator fuel pickup is the line that stops 3/4 of the way up the pump):
Fuel pump | lw5315us | Flickr

Hope that give you some ideas,

Rich

2003 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #8 –
Thanks Rich. Larry's pictures were very educational for me. I have been looking all over the web for this. If these were in the Lazy Daze Companion I must have missed them.
I did not ask the shop that replaced my fuel pump, some time ago, to look at that short section of fuel hose inside the tank to replace it, because I was not even aware of it. I am just an amateur mechanic who enjoys taking care of my own equipment since the early 1970's. So far it has saved me a lot of money over the years. Even approaching 89 I still do not mind to crawl underneath our Lazy Daze. It just is a little harder than a few years ago. I keep telling my wife that it is part of my excersize.
I have learned quite a bit from the Lazy Daze Owner's website, and especially Larry, the Companion and various other sites on the web.

Aad
2001 MB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #9 –
Hi Aad; The short section of hose is outside of the tank, but nestled up at the top. That makes it hard to get to to replace it. That is why it should be replaced when the tank is dropped.  Keep up the good work, you are an inspiration to those of us younger.  RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #10 –
I doubt if the problem is fuel pump related. The pickup tube a rigid part of the fuel pump assembly and should not move.
If the upper generator fuel line has never been replaced, there is a good chance it's cracked and is the cause of the lack of fuel, the fuel pump is pumping air and not fuel. As the fuel tank's level is raised, less vacuum is needed to pull fuel, it may start to siphon, allowing fuel flow to the carburetor.
I was able to change the upper hose on our 23.5' FL by partially lowering the fuel tank, it takes long arms to reach the fittings and was an involved job.
I do not know if a Mid-Bath can be changed this way, not requiring to completely lower the fuel tank.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: 4000 Onan Genset fuel pump replacement for 2001 Midbath.
Reply #11 –
Ron and Larry,
You may call it being stubborn instead of being an inspiration, Ron.   That is closer to my Dutch heritage.
Since my generator seems to be running now, I'll leave this project alone for the time being. Especially just having my tank filled up. However, it could be my next project, if necessary.

Aad
2001 MB