Cummins Onan 2500w LP - Fix for No Start - Fiberglass RV
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Old 08-01-2018, 02:04 PM   #1
Name: Darryl
Trailer: Bigfoot
Posts: 48
Cummins Onan 2500w LP - Fix for No Start

This is a one solution that fixed my Onan 2500w LP gas fueled generator on a 2008 Bigfoot 25B21RB trailer. The generator had run perfectly with quick starts and running under full load last season before storage over 6 months.
This summer the Onan generator engine turned over fine, but with no start and no firing.
Online research suggested a trick to “hand choke” to start by placing fingers over the generator’s intake opening after removing the air filter. The Onan started repeatedly doing this and would run under full load for an hour, but would not start again with engine hot or cold - without using fingers to hand choke to start immediately. This proved to me the problem was exclusively the starting system.
Online research also suggested the “demand LP gas regulator” vent hose, found at the lower left of the Onan door panel, was a likely culprit of NO start problems. The rubber vent hose reportedly is often clogged by insects including wasps and spiders. I initially cleared the first 12 inches of the rubber hose by pushing a 10 gauge electric wire and found no obstructions.
BUT at 20 inches into the hose bug parts were found and cleared using a more flexible 14 gauge electric wire and the Onan generator starts immediately and runs under full load. The rubber vent hose leading to the demand regulator can NOT be easily removed for cleaning as it is buried deep in the engine.
A stainless steel fine mesh filter has been custom made from materials available online and installed on the exposed outlet of the rubber vent hose (connected to the LP gas demand regulator).
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