[Steve NZ]

Hi ... my starter relay just chatters when I turn my ignition to start position.

I have ...
Checked all connections at start relay are clean.
Start relay pulls in with ign key so long as the lead to the start motor is disconnected
That the starter motor actually works when bypassing the relay
The battery is good ... used new large 12v battery out of my boat
Fuel pump runs up to pressure when key is turned on

It’s as if the starter motor, when engaged, is pulling the voltage down sufficiently to drop the starter relay coil out ... the motor disengages ... the voltage goes back up ... the relay then pulls in ... and the whole cycle starts again .... ANY IDEAS?

[NMKawierider]

Hi ... my starter relay just chatters when I turn my ignition to start position.

I have ...
Checked all connections at start relay are clean.
Start relay pulls in with ign key so long as the lead to the start motor is disconnected
That the starter motor actually works when bypassing the relay
The battery is good ... used new large 12v battery out of my boat
Fuel pump runs up to pressure when key is turned on

It’s as if the starter motor, when engaged, is pulling the voltage down sufficiently to drop the starter relay coil out ... the motor disengages ... the voltage goes back up ... the relay then pulls in ... and the whole cycle starts again .... ANY IDEAS?

And..the engine isn't seized or partly seized for sure? Starter relays "click" or rapidly cycle usually because of one main reason, and that is the demand exceeds the supply....either by the starter itself or by the relay trigger. Now the load can increase with bad starter motors or an engine that starter is having a problem rotating, or the power supply and/or ground to the relay can be weak because of a bad connection..which can be the switch or even an internal wire crimp in the main fuse holder..or any other corroded connection,.. bad ground, a battery that's depleted or has an open/damaged cell. Just need to test for power but after all cables and groundings are checked and tested.

[Steve NZ]

I tend to agree with you about the starter motor drawing a large load ... the start relay is new as when it first started the chattering I assumed a faulty relay. But the new one does the same. The engine runs fine. I started it by shorting across the starter relay lugs ... starter motor turned over and engine runs ... but I did notice excessive arcing and sparking across the terminals when I shorted them. Maybe the starter motor has a problem ... faulty windings or such??

[NMKawierider]

I tend to agree with you about the starter motor drawing a large load ... the start relay is new as when it first started the chattering I assumed a faulty relay. But the new one does the same. The engine runs fine. I started it by shorting across the starter relay lugs ... starter motor turned over and engine runs ... but I did notice excessive arcing and sparking across the terminals when I shorted them. Maybe the starter motor has a problem ... faulty windings or such??

Can always test the amp draw of the motor under load and see.