Just bougt a nice looking MEP002a at GL Fort Lewis. 75 hours since full reset. She starting right up after installing filters, putting in new batteries, oil etc but dies as soon as I let the master switch return from start to run and prime. The bendix on the starter kicks out so I can keep it running by keeping the switch on start...tried if for 15 seconds or so but switch seems to kill the engine every time it flips back to run. I've looked at the TM and can't make sense out of the wiring diagram. The battery indicator is bouncing all over the place. I would very much appreciate some guidance. I can turn bolts but electrical isn't my strongest area.
You will get comments about searching the archives...so do that now. Short answer is you should find threads that talk about the safety circuit that has two components - - 1.) Oil pressure switch and 2.)Overheat switch. When you release the starter knob it energizes that circuit and if either of those sensors is defective (or doing its job) the set will shut down. You can bypass this safety circuit for trouble shooting by removing one of the leads on the oil pressure sensor---if it keeps running then either oil or air temp is defective (or you are not making oil pressure).
They have a circuit that is energized to keep the engine running after a few seconds of the starter being engaged. 15 seconds should be more than sufficient. It could be something else, but I would say either your shut-off solenoid is bad/mis-adjusted or you've got no oil pressure. That's the first place to start.
Check TM 5-6115-584-12 & 34 for the troubleshooting procedures.
Most often, it is the low oil pressure switch. Less common is the missing K1 relay, located in the upper right corner of the control cubicle. This relay can fail but it has a spare pole so take it out and flip it over. It is symmetrical with respect to rotation (you cannot install it wrong).
Yes, there is a 900 RPM starter cut-out. Definitely check for oil pressure, the cut-out switch breaks at 14 PSI. They are susceptible to water intrusion (Hobbs manufactured style) which corrodes the piston, freezing it against pressure. They won't leak as the diaphragm is very tough (Kapton film). But if the piston won't move, the contact won't be made. The starter switch over-rides this safety system in series with the over-temperature switch. The over-temp can be checked with an ohmmeter. This switch is the Cannon plug near the hot air tube to the air cleaner. Should be closed under all normal conditions.
As far as bypassing the low oil pressure switch, just hook both screw terminal eyes to one screw. The switch is normally open, closing on pressure. VERIFY you have oil pressure before running with the switch bypassed!
oil preasure safty is a common failure. remove one of the leads and connect it to the other. be sure you show oil preasure on your gauge. high engine temp. located behind the discharge air louvers is another. put a meter on your batteries and see what you have that gauge could be defective. you should see somthing like 26-28 volts dc if the charging circuit is working properly. dont keep it in the start position to long 15 sec. max.
Thanks to all. It was the oil pressure sensor. She's running great....but throttle cable broke. Two steps forward and one step back. I'll check the classifieds but any suggestions on where I can source a cable would be most helpful. Thanks to all again. It's a great site and I appreciate the help and counsel.
For the cable -- If real surplus is pricey try a standard "Lever and knob control cable assemblies" at Mc Master-Carr (McMaster-Carr). I got one with a cable end and added the clevis end to match the original. Biggest pain with that is the dozen or so bolts to take off the fan shroud so you can get at the throttle
Thanks to all. It was the oil pressure sensor. She's running great....but throttle cable broke. Two steps forward and one step back. I'll check the classifieds but any suggestions on where I can source a cable would be most helpful. Thanks to all again. It's a great site and I appreciate the help and counsel.
If you feel the stock cable is too lightweight see my MEP-016B post further down where I made a heavy duty cable by shortening a much stouter truck PTO cable. Swaging the home made end is the only part that some may not be able to do easily. That big bolt cutter swage tool in my post was only $25 at Home Depot. I think it is designed for wire fences so if yiou know a farmer they may have one. cutting the cable down was easy. The whole project only took an hour or so. McMaster is good lead to find a cable. McMaster is good for lots of stuff!!
MEP002A starts and dies-Switch?
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