Ignition Short

[Marc H. Pearl]

Can someone explain how the ignition is wired so that I can try to find a short? You know the ignition switch has an audible alarm that shuts off when the engine fires. Well my alarm isn't shutting off. I can manually turn the switch off to stop the alarm without shutting down the engine, but my tack reads incorrectly when I do that. Any suggestions?

 

[Warren Holybee]

Be cautious, as low oil pressure will cause the alarm to stay on. If low oil pressure is the cause, then it will ruin the engine to run it!

Owners manuals are in the Morgan 38 Background, History, Reference section and include some electrical drawings.(link below)
If the alarm isn't shutting off, check the oil pressure and temp sending units, the alternator lamp (bulb) and that the alternator is working. To elaborate, that alarm isn't an ignition alarm, it is an alarm that something is wrong with the engine, either oil pressure, over temperature, or the alternator. It alarms before you start the engine because there is no oil pressure when it is not running.

Assuming that none of those things are wrong, then check the sensors for them.

Morgan 38 Background, History, Reference

 

[Marc H. Pearl]

Damn... I didn't even think of that. Thanks Warren. I have some investigating to do.

 

[Marc H. Pearl]

I feel quite embarrassed. ALWAYS TRUST YOUR INSTRUMENTS! What would cause low oil pressure? I thought I was taking off the oil pressure sending unit to replace it but was told this is just an alarm switch. Where is the actual oil sending unit located on the engine?

 

[terry_thatcher]

If you have a Perkins, there are 2 sending units low on the block, port side. If a Yanmar, I don't know. Check archives. May be photos.

 

[Marc H. Pearl]

Replaced the oil pressure sender and also the oil alarm switch. Solved the alarm problem but the new oil pressure gauge is maxed out and reading 80psi +. Did I maybe buy the wrong unit? The guy said it was a 100 psi gauge.