Interesting discussion. I was just working on mine and was thinking the valve wasn't opening because the pump wouldn't prime the carb so I pulled the
valve and found it was in fact failed....open! Fuel just flows straight through it when held vertically and disconnected from power. Who knows how
long it's been like that.
But as to the point that the carb fuel will be drawn down without the solenoid valve, that's not possible as the fuel inlet on the carb is above the
fuel level in the bowl. It certainly can evacuate the pump and filter if you use one but none of those will delay starting if the carb bowl is full.
I also doubt that air flowing back through the system can starve the motor driven fuel pump but that's only a hunch. Easy enough to put a vacuum
gauge on the line and see which brings me to the point of my post...how much suction is the Onan pump supposed to produce?
Mine has very little and I didn't have my gauges handy to check but I really had to pay close attention to see that there's any at all. It hasn't
been long since I disassembled and cleaned it so I doubt it's fouled but the check valves could be leaky from age.
As an aside, you know how you start to tackle one specific problem and pretty soon you're up to your neck in issues? My goal today was to test the
low oil pressure switch since the Onan would start but shut off as soon as you released the start switch. As I sat on the ground beside the genset, I
figured I might as well pull the side cover off to expose the pressure switch while I was taking the cover off the control board. Well don't you know
it...one of the bolts holding the cover snapped off flush in the head with the slightest pressure.
So I stopped there and got my drill, left-hand drill bits, tap, sharp punch, hammer and propane torch. A little later the remains of the bolt were
extracted and threads cleaned up. I reseated the connector on the pressure switch just to make sure and then tried to start the generator and no
dice! It started fine a few days ago. Grabbed a 12 V source and attempted to prime the carb and the pump ran continuously building no back pressure
unlike a few days ago. That launched me on the troubleshooting of the solenoid valve. I don't imagine they pull much vacuum but it appeared mine
couldn't pull any fuel from a nearly full tank.
--
1978 Eleganza II
valve and found it was in fact failed....open! Fuel just flows straight through it when held vertically and disconnected from power. Who knows how
long it's been like that.
But as to the point that the carb fuel will be drawn down without the solenoid valve, that's not possible as the fuel inlet on the carb is above the
fuel level in the bowl. It certainly can evacuate the pump and filter if you use one but none of those will delay starting if the carb bowl is full.
I also doubt that air flowing back through the system can starve the motor driven fuel pump but that's only a hunch. Easy enough to put a vacuum
gauge on the line and see which brings me to the point of my post...how much suction is the Onan pump supposed to produce?
Mine has very little and I didn't have my gauges handy to check but I really had to pay close attention to see that there's any at all. It hasn't
been long since I disassembled and cleaned it so I doubt it's fouled but the check valves could be leaky from age.
As an aside, you know how you start to tackle one specific problem and pretty soon you're up to your neck in issues? My goal today was to test the
low oil pressure switch since the Onan would start but shut off as soon as you released the start switch. As I sat on the ground beside the genset, I
figured I might as well pull the side cover off to expose the pressure switch while I was taking the cover off the control board. Well don't you know
it...one of the bolts holding the cover snapped off flush in the head with the slightest pressure.
So I stopped there and got my drill, left-hand drill bits, tap, sharp punch, hammer and propane torch. A little later the remains of the bolt were
extracted and threads cleaned up. I reseated the connector on the pressure switch just to make sure and then tried to start the generator and no
dice! It started fine a few days ago. Grabbed a 12 V source and attempted to prime the carb and the pump ran continuously building no back pressure
unlike a few days ago. That launched me on the troubleshooting of the solenoid valve. I don't imagine they pull much vacuum but it appeared mine
couldn't pull any fuel from a nearly full tank.
--
1978 Eleganza II
