We have a 742 (don't Laugh)n It has been coverted to propane. it has a mitshubisi engine. It starts and runs just fine but when the ignition is switched off it continues to run. we have checked the switch and the ballast resistor..any help would be appreciated. Thank you
Sounds like a bad fuel shutoff solenoid.
So how do you normally do a shutdown? shut propane tank off and wait... or pull center spark wire at cap... or....
It's standard ignition. Just like you would any other piece of equipment.
yeah..good call. would that still apply to a propane coversion?
I'm with trashman, althought I've never worked on a 742, and NEVER worked on a Bobcat powered by propane, pretty much every industrial propane engine I've worked on has a solenoid valve in the supply line to the carb that's controlled by the ignition wire to shut off propane when you turn the key off.
yeah im looking at this as we speak. One quick question...would one side of this fuel cut off switch be wired up to the ballast resistor? Thanks for everything so far!
It's possible, but not necessarily necessary. The ballast resistor would there to regulate power to the ignition coil, but the propane solenoid could be connected to the terminals of the resistor since that's the ignition circuit anyway. Point is, the propane solenoid doesn't care whether it gets power from the resistor or not, just that it gets ignition power.
Understood. I don't have alot of propane experience so i really appreciate the help. The reason i asked was because someone stated that the solenoid was controlled by the ignition wire.The the fuel cut solenoid is wired to one side of the ballast resistor. I took an ohm reading on the ballast resistor at Rx1`with all wires disconnected. and it read 4 i understand if they read anything but a 3 there junk..is that correct? and my thought is if it is junk that this might be causing the problem .
In all honesty, I can't recall. Not to be unhelpful, but I try to forget what I know about spark engines as I dislike them that much. But to make things simple, if in fact you do have a propane solenoid in the supply hose to the carb, connect it to the ignition wire terminal on the resistor. The other terminal on the resistor should go the the + terminal on the ignition coil.
It's all irrelevant to the original problem, what you have is power getting to the coil with the switch off. Question is, from where? Starter bypass could be stuck on, never seen one but it's theoretically possible. Could be miswired somewhere, and some other circtuit is feeding it. Could be something to do with the alternator, if it's crossconnected somewhere the alternator will feed electricity to the coil and no shutdown. With the engine off, and the switch off, check for voltage at the ballast resistor. If there is voltage, track down where it's coming from. Assuming no voltage, switch on and check again... voltage now. Start engine. Turn switch off, engine continues to run? Check voltage again... voltage now at ballast resistor? From where? May take several tries to track it down.
Thank you very much. This makes sense.
That's exactly how it's wired. Thanks for the help.
Another thing I have seen is someone will replace/change and alternator and wire it wrong so it will power the ignition circuit even though key is off.