willie59
Administrator
Ok, not necessarily heavy equipment, but I ran across a problem I've never seen before and thought it was interesting. Maybe some out there are aware of this, I've just never seen it. Since I'm now working at a steel fabrication and erection shop, one of the things I work on are Miller Bobcat welders, a freaking pile of them! Kohler Commander V twin gasoline engines. One showed up in my work area with a tag on top "can't keep welder running". Hmm.
Fire it up, lit up just fine. Started burning some sticky rods, after a few minutes, sure enough, it died. Hmm, sounds like a fuel problem. Changed fuel filter. Nope. Hmm, possibly the pulse pump, put a new one on it. Nope. Hmm. Maybe problem with pickup tube inside tank. Pulled it out, all good there. Pulled top of of the carb to check inside, all tidy. Maybe the anti-diesel solenoid on the carb is losing power, put a 12V jumper to it straight from starter. Nope. Hmm. Maybe anti-diesel solenoid is going bad, changed it with one from my parts pile, nope. Hmmm. Damn...I've done everything, what's left?
That's when I recalled that some engines like this monitor oil pressure and will shut the engine down if it senses low pressure. Don't know if these engines do but I've check everything else. Well maybe it's just low on oil. Pulled the dipstick. No, not low...overfilled! What??? I marked the stick where the oil level was, held it beside the tube to gauge where the oil level was inside the engine, it was about 1 1/2" below the center of the crankshaft. Then it hit me, the thing I've never seen before as most folks don't overfill their oil sump, is it possible?
I know these pulse fuel pumps work from the changes in crankcase pressure from the pistons moving up and down and those pulses of pressure is what makes them operate and pump. But that's with a proper oil level with oil remaining pretty much flat in the bottom of the sump. But with the oil filled to 1 1/2" below the center of the crankshaft, that would mean the lobes of the crank are slapping that oil in the sump all over the place inside the engine. Could this be disturbing the normal crankcase pressure inside the engine affecting the fuel pump? Drained the oil to the proper level on the stick, fired it off, burned rod after rod after rod, ran flawlessly. Well I'll be damned, learned something new today, overfilling oil sump on a small engine with a pulse pump will shut it down because it wacks out the internal pressure that operates the pump. Never seen that before.
Fire it up, lit up just fine. Started burning some sticky rods, after a few minutes, sure enough, it died. Hmm, sounds like a fuel problem. Changed fuel filter. Nope. Hmm, possibly the pulse pump, put a new one on it. Nope. Hmm. Maybe problem with pickup tube inside tank. Pulled it out, all good there. Pulled top of of the carb to check inside, all tidy. Maybe the anti-diesel solenoid on the carb is losing power, put a 12V jumper to it straight from starter. Nope. Hmm. Maybe anti-diesel solenoid is going bad, changed it with one from my parts pile, nope. Hmmm. Damn...I've done everything, what's left?
That's when I recalled that some engines like this monitor oil pressure and will shut the engine down if it senses low pressure. Don't know if these engines do but I've check everything else. Well maybe it's just low on oil. Pulled the dipstick. No, not low...overfilled! What??? I marked the stick where the oil level was, held it beside the tube to gauge where the oil level was inside the engine, it was about 1 1/2" below the center of the crankshaft. Then it hit me, the thing I've never seen before as most folks don't overfill their oil sump, is it possible?
I know these pulse fuel pumps work from the changes in crankcase pressure from the pistons moving up and down and those pulses of pressure is what makes them operate and pump. But that's with a proper oil level with oil remaining pretty much flat in the bottom of the sump. But with the oil filled to 1 1/2" below the center of the crankshaft, that would mean the lobes of the crank are slapping that oil in the sump all over the place inside the engine. Could this be disturbing the normal crankcase pressure inside the engine affecting the fuel pump? Drained the oil to the proper level on the stick, fired it off, burned rod after rod after rod, ran flawlessly. Well I'll be damned, learned something new today, overfilling oil sump on a small engine with a pulse pump will shut it down because it wacks out the internal pressure that operates the pump. Never seen that before.
