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DavidM49's avatar
DavidM49
Explorer
Sep 23, 2013

Onan 5500 Marquis Gold Fuel Pump location

Hello all,

My genset will not start or fire at all. I changed the oil last month and it started fine. Went to run it last night and it would not start. Not sure I am getting fuel. Will do some more diagnostics tonight like pull fuel line to carb to ensure I am getting fuel. All that being said, can anyone help me determine where the actual fuel pump resides. I imagine is is fairly accessable but any advance assistance is appreciated. After reading numerous posts about this genset over the years, it seems like my hunt and surge issue during hotter weather may be related to the fuel pump overheating. It is so frustrating though, used it for 4 days after numerous repairs in the hottest Michigan weather ever last summer, ran like a top. Now it has started hunting and surging again. Thanks for your help!!!
  • JoeH's avatar
    JoeH
    Explorer III
    Sep 25, 2013
    OldF**t wrote:
    DavidM49 wrote:
    I could hear the pump running while trying to prime the carb. It was like a hammer sound more than anything. That being said, I got nothing out of the fuel line when trying to prime the carb.

    Well the next step would be pulling the hose off of the pump filter to see if fuel is available from the tank. The tank should be half full or greater as the generator fuel line pickup is not at the bottom of the tank. Also the line to the tank could be bad or have a leak which would cause the pump to suck air instead of fuel.


    Yep-- common to have cracks and resultant air leaks in the tank to pump line.
  • OldF__t's avatar
    OldF__t
    Explorer
    Sep 24, 2013
    DavidM49 wrote:
    I could hear the pump running while trying to prime the carb. It was like a hammer sound more than anything. That being said, I got nothing out of the fuel line when trying to prime the carb.

    Well the next step would be pulling the hose off of the pump filter to see if fuel is available from the tank. The tank should be half full or greater as the generator fuel line pickup is not at the bottom of the tank. Also the line to the tank could be bad or have a leak which would cause the pump to suck air instead of fuel.
  • DavidM49's avatar
    DavidM49
    Explorer
    Sep 24, 2013
    I could hear the pump running while trying to prime the carb. It was like a hammer sound more than anything. That being said, I got nothing out of the fuel line when trying to prime the carb.
  • OldF__t's avatar
    OldF__t
    Explorer
    Sep 24, 2013
    DavidM49 wrote:
    Thanks guys for the the help. Took line off of filter before carb and hit prime and not a drop of fuel came out of the line. Now the challenge is to find the airtex brand pump versus paying premium for the Onan branded pump. Thanks again!

    So we can assume that you didn't hear the pump running? Additionally Onan has a straight pipe replacement for the filter on the carb. That carb filter has been troublesome/leak prone for a lot of folks. As long as you are going to replace the pump you might as well get rid of the carb filter, replace the pump filter, and replace the hose to the carb.
  • DavidM49's avatar
    DavidM49
    Explorer
    Sep 24, 2013
    Thanks guys for the the help. Took line off of filter before carb and hit prime and not a drop of fuel came out of the line. Now the challenge is to find the airtex brand pump versus paying premium for the Onan branded pump. Thanks again!
  • Dusty_R's avatar
    Dusty_R
    Explorer
    Sep 24, 2013
    othertonka wrote:
    First take the front cover off and find the START/STOP button, lower left corner. Note that the STOP button is also a PRIME button. Press and hold down the PRIME button and you should hear the fuel pump start to click. Let it prime until the clicking stops or at least slows down. While it is clicking locate the sound of the pump and you will find it underneath the left front corner of the gen set, clamped to a rubber fuel hose and will have a filter screwed into the pump.
    Priming might also assist you in your hard starting problem.


    You need to hold that stop button for a few seconds before the pump starts, there's a time on delay.
  • othertonka's avatar
    othertonka
    Explorer
    Sep 23, 2013
    First take the front cover off and find the START/STOP button, lower left corner. Note that the STOP button is also a PRIME button. Press and hold down the PRIME button and you should hear the fuel pump start to click. Let it prime until the clicking stops or at least slows down. While it is clicking locate the sound of the pump and you will find it underneath the left front corner of the gen set, clamped to a rubber fuel hose and will have a filter screwed into the pump.
    Priming might also assist you in your hard starting problem.
  • bobsallyh's avatar
    bobsallyh
    Explorer II
    Sep 23, 2013
    As you are looking at the front of the genny, underneath and a little bit to left of the oil filter. If I remember correctly it is held on by a clamp to the genny base.

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