Help starting engine

[rwarre]

Tried to start up my 7A, Lyc O320 nothing happened. I have been using Nuckols basic wiring diagram. Starting trouble shooting with no voltage at the starter, but I have voltage at the mag switch. The switches seem to be wired correctly but I have to investigate further. Any suggestions for trouble shooting would be greatly appreciated. Thanks

[lostpilot28]

I would make sure you have the right connections on the Starter Solenoid. I managed to get one of my contacts on the wrong post. 8 years as an Avionics guy in the U.S. Navy...go figure.

[avee8tor13]

rwarre, you are not giving a lot of info on this one but let's start with the battery. Take a volt meter and verify you have twelve volts across the battery terminals (the positive and negative terminal).

I suspect you are using a solenoid between the battery and the starter. If so are you getting twelve volts between the solenoid battery terminal and ground? Make sure the master solenoid is activated or turned on before testing.

Now, let's assume the above was ok. You will need to connect the volt meter or a test light to the sol terminal on the starter solenoid then turn the ignition all the way to the crank (spring loaded) position and note if the test light or volt meter register 12 volts. If so, then the switch is probably wired up correctly. The next step is to make sure when the starter switched is turned to the cranking position, the starter terminal on the starting solenoid should have twelve volts. If not the solenoid may be bad. If it has voltage on all three terminals while in the cranking position, you may have a faulty starter (usually a bad spot on the commutator on the armature) .

Also make sure you have a good ground on the engine case and airframe.

Hope this help.

[frankh]

No volts at starter terminal?..So it doesn't crank right?

Then go to the contactor. Is it pulling in when you activate the starter circuit?

Does it get volts on the little terminal?....If so then the solenoid is dead (assuming you got a ground connection)..If not then its the wire feeding the switch.

Pretty simple...Start there and follow the fault.

Frank

[Bob Axsom]

It has been a while and I don't remember the exact details but I had no details on the hookup requirements on the solenoid for the starter. I assumed where the coil terminals were and the contact terminals to carry the heavy load for the starter. My assumption was wrong with respect to the coil hookup and when I got it figured out and hooked it up correctly it worked perfectly. As I recall there were two small terminals which I assumed were the coil terminals - wrong! I bought the solenoid from Aircraft Spruce and there was a note with it which helped me figure it out - the hookup was not visually intuitive. You may have a similar problem.

Bob Axsom

[Mike S]

Did you by any chance use a master solenoid for the starter???

Some solenoids require external power to the coil, and are internally grounded, while some have the coil hooked to power internally, and need ground supplied to the activation stud.

Good luck, also check the diode when you are done, they fry easily.