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Onan Fuel Pump


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Today I decided to see if our Onan 5500 genny would run.  Short answer.....no.  To be fair, the last time I ran it was 16 moths ago, when I tested it during the Great Texas Blizzard of 2021.  It fired up and ran smoothly, so I shut if off and forgot about it.  So now here we are.  

After fiddling around with the genny for a bit and finding the float bowl dry, I tried a sniff of ether and it fired.. Okay, pull the hose and test everything.  Yep, red wire has juice, black wire has ground, pump sits there silently, until "awakened" with a 4 oz. ball peen hammer.  (Yes, some farmers know how to use small hammers too.)  Pump only runs a few seconds and quits until awakened again.  Susan wasn't very keen on the notion of my hanging a hammock under the coach so she could keep the thing running while I got my beauty rest, so I called Father Google and asked if he knew where to purchase a replacement.  My goodness.  Genuine Onan/Cummins runs about $140 plus shipping/taxes for this simple device.  I found a cheap knock off for $18, shipping and sales tax included.

So, I poked the "Heck Yes" button and it should be here by 6/30.

Hope it holds up for a couple years.

Edit....  In the time it took me to type this, the order has been processed and shipped.  That's service.

Edited by rickeieio
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Maybe you read this over a year ago ::


Anyway , I did the same as you . For less than 20 bucks the fuel pump I installed is still doing fine , having put in more hours of service than we would normally have used the generator . ;)


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Mine was simply a low oil situation!!!!!  Actually, when Bill Burton helped get mine running when city power was out, he pointed out something about a sticker that said "check oil level every time before starting"!!!!  And he didn't add that much to it!



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What I ordered is a direct replacement for the factory pump. mounted in the same pita location.  Unfortunately, the line from the tank to the pump is enclosed under the trailer, so this option is the lesser of evils.  It shouldn't take more than a few minutes, but would be easier if I didn't have "old farmer hands".

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The one thing I found out when mine went out is Onan uses a low pressure fuel pump. If a 7-9 lbs pump is used it will hold the needle open. I think it is a 3 lbs max pressure pump. I went with a aftermarket pump as well. 

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15 minutes ago, Star Dreamer said:

If you are going to the Balloon Fiesta this year, you may want to make sure it runs. We didn't need to use ours a lot but we did use it to top of batteries a couple of times. 

That's our driving force here.  We have no solar, but with the new batteries and a working genny, we should do fine.  I've been toying with bringing our Yamaha 3000inverter rather than running the bigger unit.  But, we have 56 gallons of fuel capacity for the Onan, plus auto-start, if I can figure out how to enable it.

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Well, the new pump arrived yesterday.  It shipped from a warehouse about 10 miles from our house, even though the seller is in California.  This was from the Bay of Fleas, which I hate almost as much as Amazon.

The pump was the same as the original, except the mounting tabs were off by about 1/4".  Just enough that I couldn't fudge it, and by the time I realized the holes didn't match, I had fought it into place.  A couple of fender washers were pressed into duty and all's well.

But wait, there's more.  There's a filter screwed into the pump.  Same kind of filter as on the gas line going to the carb on your 72 Maverick.  Do you think the local NAPA has those?  Of course not.  And it's $40 from Onan, and who knows when you'll get it.  Blew out the old filter with carb cleaner and put it together, making note to install a real filter up stream.  Hit the "prime" button and gas gushed out like it's supposed to.  Hooked up the line and punched the starter button and glorious noises came forth..........as did a stream of gas from the filter screwed into the carb.  Wouldn't you know, same number as the one on the pump.  Redundant filter.

My Garage Princess asked if I was going to bite the bullet and order the filters.  Heck no!!!  I rummaged around and found the appropriate male npt to 1/4" hose barb fitting and she's up and running.

It just so happens, I have a filter base in the parts bins, intended for a transfer pump in a service truck.  I think that and a 10 micron filter will do nicely, for way cheaper than the crap from Onan.

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