Log In | Register
Skip to main content
Topic: Onan 4000 generator fuel pump - OEM the best way to go? (Read 180 times) previous topic - next topic
0 Members and 2 Guests are viewing this topic.
Onan 4000 generator fuel pump - OEM the best way to go?
I have a Onan 4000 microquiet generator and have succumbed to the fact that I should probably replace the original fuel pump and fuel filter after 255 running hours. After about 30 minutes of running smoothly under load, it seems to surge (gets low and and then back up to proper running speed) and I've churned more Seafoam through a direct gas line to the genny than I'd like to admit so I don't believe the carb is the issue.

Has anyone successfully purchased an aftermarket fuel pump they like or is it work spending the $100+ for an OEM Cummins one that looks identical to the Chinese aftermarket ones you can buy on Amazon, eBay etc. From the Youtube videos I've watched, it looks like quite the pain to do this job but the pain of spending much more money at a Cummins dealer would probably pain me more and I wouldn't have learned how to fix it on my own.

We'll be roadtripping for a couple of weeks this summer while I ride RAGBRAI again across Iowa so I really really would like a reliable generator running when we boondock in 100 degree heat.
Joe B.
2008 26ft  grey/white Rear Bath
Family of 5 hitting the open road as much as we can.
Re: Onan 4000 generator fuel pump - OEM the best way to go?
Reply #1 –
In my experience OEM is the worst way to go. Three times the price and worst reliability. I got tired of replacing them.

By the way I was told by a Cummins dealer that a 4000i is coming this summer.
Harry 2006RB
Re: Onan 4000 generator fuel pump - OEM the best way to go?
Reply #2 –
Quote from: hbn7hj  - 
In my experience OEM is the worst way to go. Three times the price and worst reliability. I got tired of replacing them.

By the way I was told by a Cummins dealer that a 4000i is coming this summer.

Did you find an aftermarket one you liked? What the heck is the 4000i??
Joe B.
2008 26ft  grey/white Rear Bath
Family of 5 hitting the open road as much as we can.
Re: Onan 4000 generator fuel pump - OEM the best way to go?
Reply #3 –
Quote from: brewersarcade  - 
I have a Onan 4000 microquiet generator and have succumbed to the fact that I should probably replace the original fuel pump and fuel filter after 255 running hours. After about 30 minutes of running smoothly under load, it seems to surge (gets low and and then back up to proper running speed)

I would first run a tube from the fuel pump input into a container with enough gas to run > 1/2 hr, and see if the symptoms occur. If not, a good chance the problem is fuel starvation from air getting into the supply line from a deteriorated rubber coupling hose on top of the gas tank.

Steve
2004 FL
2013 Honda Fit
Re: Onan 4000 generator fuel pump - OEM the best way to go?
Reply #5 –
Quote from: Steve  - 
I would first run a tube from the fuel pump input into a container with enough gas to run > 1/2 hr, and see if the symptoms occur. If not, a good chance the problem is fuel starvation from air getting into the supply line from a deteriorated rubber coupling hose on top of the gas tank.

Steve

Yup I've done this previously mixed with Seafoam with the same surge issue. The supply line hose issues aren't typical on later LDs like mine.
Joe B.
2008 26ft  grey/white Rear Bath
Family of 5 hitting the open road as much as we can.
Re: Onan 4000 generator fuel pump - OEM the best way to go?
Reply #6 –
I went with an eBay carb for an ATV it was just so much cheaper that I couldn't resist. That will be the last time I do that.

Jon
1994 MB
Re: Onan 4000 generator fuel pump - OEM the best way to go?
Reply #7 –
Quote from: brewersarcade  - 
Has anyone successfully purchased an aftermarket fuel pump they like

I bought an AirTex from Amazon in June 2020 and it's been fine so far. 

Amazon.com: Airtex E11007 Electric Fuel Pump for Onan Generator Set : Automotive

The one I bought isn't available, but it looks like there are replacements with good reviews. 

Rich
As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
2003 MB