Posted: 6/20/2005 7:03:46 PM EDT
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A buddy of mine called and is having a problem with a gas generator in his motor home. The engine will run as long as you hold the start button down when you release the button it dies. I've haven’t looked at it yet but thinking starter relay. Any other ideas? I don't know who makes this unit he is going to call me later after he looks. |
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We had this exact problem in a 1976 Ford Pinto. It would start when you turned the key to start, and cut off when you let it go (when it should be in the 'run' position). After much head scratching, the problem was that the key switch mechanism was worn, and 'run' had become 'off'. I remember this well, as it was my first mechanical troubleshooting 'In your face BIOTCH!' to my dad, as I called it when he was chasing his tail in the fuel system. |
That is called the ballast resistor. Its purpose is to reduce primary coil current to preserve point life. Generators usually have magneto ignition and therefore, no ballast resistor. The real solution is in the oil pressure safety switch or oil pressure itself. Check oil pressure when it starts. If no pressure at governed speed, the engine needs work. This is rare, it is usually the switch not making contact. Check with ohmmeter with it disconnected and engine off. Then start and hold the button and check the switch again...10-100 ohm scale is fine. If no change, replace. You DON'T want to bypass the oil pressure safety switch because it will save the cost of the engine... I'll assume this is either a Generac or Onan. |
That's a spot-on diagnosis - Some generators bypass the low oil pressure shutdown switch while the starter is cranking, but look for good oil pressure almost immediately afterwards...The engine will start with zero oil pressure, but won't continue to run that way...which also means that the problem could be as simple as not having enough oil in the crankcase. Also, some models supply 12 volts to the electric fuel pump through the starter switch while the engine is cranking, and then rely on a 12 volt winding inside the generator to power the pump after the engine starts. This is a safety feature: If the engine dies for any reason, the electric fuel pump won't continue to pump fuel indefinitely. However, if the 12 volt winding should fail, the engine will only get fuel while the starter is cranking, and will die shortly after the start button is released. |
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It is on the engine block, near the oil filter. Since it is an Onan, it could also be the temperature cutout switch which is integrated with the oil pressure cutout switch on some models. Emerald 1 models have 3 different sub-models and can be either gasoline or LPG. The manuals are well worth the cost if you have little mechanical experience. |