I posted a solution in 2006 for a failed fuel pump and circuit, including the addition of a push button prime.
That topic is closed, but I wanted to update the info as the Mr. Gasket #42S fuel pump is NOT a satisfactory replacement any more.
Mr. Gasket has changed the pump to a rather worthless plastic model and REVERSED the lines- the output is now a fixed-molded hose barb instead of a threaded connection. These installations require the INPUT to be the hose barb and the output to be a threaded hard line.
Here is a suitable replacement fuel pump for the Onan 4000 generator:
"Airtex E8251 Universal Solid State Electric Fuel Pump for Marine Applications"
Found it on Amazon for about $37 with tax.
I still had to use the adapter fitting on the output side for NPT to steel fuel line from the 2006 replacement.
I am about to add the same prime circuit to an Onan Microlite 4000 Generator in a different Class C next week.
Something to keep in mind when choosing a fuel pump. The pressures need to be close to 3-4psi. Too little and it won't be effective. Too much and it could push past the carb float and flood the crankcase and generator with gas.
Also- Not all pumps are self-priming and require gravity feed. These pumps will NOT pull gas from the RV's tank as required for these generators. The one I mention above works fine.
A tip- install the rear rubber line first, then start the output hard line and tighten it, then back it off a turn or two so the line can twist in the fitting. Install the mounting bracket using the BOTTOM bolt, as the mounting flange won't clear the generator's housing on the top bolt.
Make sure everything is tight and don't forget to check for fuel leaks before buttoning it all back up!
Edit: Here is the original post:
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/17692195.cfm
