Broncorambler wrote:
The 300 cummins starts and idles fine. Goes into high idle fine and even revs if not under load. Once in gear with brake set or driving it will stumble, rebound and then stumble again in a cycling way like running out of fuel.
My diesel mechanics scan tool shows no fuel pressure from any aux fuel pump, but it does show vac. pressure from hi pressure pump drawing fuel to the engine. Dont know for certain there is an aux pump, but assuming there is because tank is over 20 feet from the engine and seems should be one. Manual makes no mention of one tho?
On top of tank there are number of wires going thru a portal into the tank and seems like more than needed for sending unit.
Two good diesel mechanics believe Cumminns ISB300 engines have an aux pump, but could they be wrong?
Manual does mention that clogged tank vent can give issues and guess id better check it out, but didnt ghink could be culprit.
Hoping might be some good techs on the Monaco group provuded me, but busy next couple days. Thanks much for replies and advice.
On the Manual I sent you the link to. Go to the Calibrating part of the Fuel tank sending unit. You will see WHY there are more wires than you think is necessary. I was waiting for others to reply. I NEVER saw any In tank fuel pump on a Roadmaster Chassis. The fuel pick up and return is just 4 hoses. The 3rd/4th hose is for the optional Aqua Hot and Genset feeds. The good news is, since the Fuel pump system is part of Cummins, you should be able to get it fixed by a Cummins Service Center. Doug
