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Old 07-24-2021, 09:02 PM   #1
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2003 Dolphin - Onan 5500 generator question...

Folks - I was 'Wallydocking' recently in the Texas heat of Fort Stockton and my generator cut out on me a bunch of times overnight. I was sleeping (until my wife and I got overheated and woke up) when it cut out - so I'm not sure how long it ran the first couple times. The last time it cut out - it was in the real 'wee hours' and it only ran for maybe 30 minutes.

Over the duration of our trip, we used the generator a number of times for multiple hours with no problem and even repeated our overnight stay in Fort Stockton and did not have any issues... just that one night.

I've been reading the forums and there has been discussion on the 5500 Onans about replacing the fuel pump/fuel filter when this kind of problem happens so I figured - heck... like Nike says - Just Do It. I was under the generator today to see what was there, and... no pump or in line filter. I have a metal can filter topside under the cover - and discussion on the forums says they may leak and Onan has service bulletin out recommending removal and putting in a 'shunt' with a part number (seems like for $2 piece of fuel hose - just get a new line... but I digress).

I know I have a fuel pump for the generator way back at the fuel tank (because I was testing the genny one day and had fuel peeing down from the cracked fuel line. $35 of new fuel line later - no more problem). I'm thinking in my configuration - there is a rear fuel pump and not one right at the generator itself. Is this like every other Dolphin? or did someone re-rig mine at some point in the past (I've only had this thing for a year - still learning).

Any input is always appreciated.

Arden
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Old 07-24-2021, 09:22 PM   #2
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Quote:
Originally Posted by smithbill View Post
Folks - I was 'Wallydocking' recently in the Texas heat of Fort Stockton and my generator cut out on me a bunch of times overnight. I was sleeping (until my wife and I got overheated and woke up) when it cut out - so I'm not sure how long it ran the first couple times. The last time it cut out - it was in the real 'wee hours' and it only ran for maybe 30 minutes.

Over the duration of our trip, we used the generator a number of times for multiple hours with no problem and even repeated our overnight stay in Fort Stockton and did not have any issues... just that one night.

I've been reading the forums and there has been discussion on the 5500 Onans about replacing the fuel pump/fuel filter when this kind of problem happens so I figured - heck... like Nike says - Just Do It. I was under the generator today to see what was there, and... no pump or in line filter. I have a metal can filter topside under the cover - and discussion on the forums says they may leak and Onan has service bulletin out recommending removal and putting in a 'shunt' with a part number (seems like for $2 piece of fuel hose - just get a new line... but I digress).

I know I have a fuel pump for the generator way back at the fuel tank (because I was testing the genny one day and had fuel peeing down from the cracked fuel line. $35 of new fuel line later - no more problem). I'm thinking in my configuration - there is a rear fuel pump and not one right at the generator itself. Is this like every other Dolphin? or did someone re-rig mine at some point in the past (I've only had this thing for a year - still learning).

Any input is always appreciated.

Arden
Yes, of course check the fuel filter first, but having the pump back by the gas tank is actually a good thing. They didn't come that way from the factory, but fuel pumps are better at pushing than pulling, and the low pressure created by pulling the fuel through the line makes them more prone to vapor lock. The Onan in my 2004 Dolphin would shut down after 20-30 minutes every time the ambient temperature was over 90 degrees or so. I could see where the previous owner had tried all sorts of shielding etc to fix it but to no avail.

I moved the fuel pump back to near the gas tank, as recommended in an article I read about preventing vapor lock. That creates high pressure between the pump and the generator (which raisers the fuel boiling point) and I haven't had a problem since.

Hopefully the line coming from the gas tank hasn't developed cracks, as that requires dropping the tank to repair. To avoid dropping the 75 gallon tank, some have added a new pickup using a sealed off filler port that's on on the passenger side of the fuel tank. There are threads on here somewhere about that.
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Old 07-25-2021, 07:10 PM   #3
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I also own a Onan 5500 and had to do some fuel pump trouble shooting.
This Video may be helpful to you.
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Old 07-25-2021, 08:00 PM   #4
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Quote:
Originally Posted by smithbill View Post
Folks - I was 'Wallydocking' recently in the Texas heat of Fort Stockton and my generator cut out on me a bunch of times overnight. I was sleeping (until my wife and I got overheated and woke up) when it cut out - so I'm not sure how long it ran the first couple times. The last time it cut out - it was in the real 'wee hours' and it only ran for maybe 30 minutes.

Over the duration of our trip, we used the generator a number of times for multiple hours with no problem and even repeated our overnight stay in Fort Stockton and did not have any issues... just that one night.

I've been reading the forums and there has been discussion on the 5500 Onans about replacing the fuel pump/fuel filter when this kind of problem happens so I figured - heck... like Nike says - Just Do It. I was under the generator today to see what was there, and... no pump or in line filter. I have a metal can filter topside under the cover - and discussion on the forums says they may leak and Onan has service bulletin out recommending removal and putting in a 'shunt' with a part number (seems like for $2 piece of fuel hose - just get a new line... but I digress).

I know I have a fuel pump for the generator way back at the fuel tank (because I was testing the genny one day and had fuel peeing down from the cracked fuel line. $35 of new fuel line later - no more problem). I'm thinking in my configuration - there is a rear fuel pump and not one right at the generator itself. Is this like every other Dolphin? or did someone re-rig mine at some point in the past (I've only had this thing for a year - still learning).

Any input is always appreciated.

Arden
These might be helpful https://www.dropbox.com/sh/z713aum8w...mJkUrwq_a?dl=0
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