Usually bad battery connections, and those at the solenoid involving the
brown wires or battery cable, causes a chattering solenoid, as with the
solenoid operated and the very low resistance load of the motor connected,
the voltage to the solenoid and motor drops very significantly, often below
that at which the solenoid will hold in. This causes the solenoid to
release, which disconnects the motor, the voltage rises, the solenoid
operates again and so on. But the crucial test is what does the ignition
warning light do when you turn the key to crank? If it stays relatively
bright then the solenoid isn't connecting power to the motor - could be
solenoid contacts, motor brushes etc. If it dims right down then it is, but
either there is insufficient power to turn the motor (although there should
still be a very small movement as it tries to) or the starter pinion is
jammed in mesh with the flywheel.
Also with a 74 there is a starter relay as well as the solenoid, and it may
be that it is this you can hear and not the solenoid itself. The relay is
mounted high on the inner wing by the fusebox and makes a 'click', the
solenoid is lower down of course and makes a 'clonk'. If it's the relay you
can hear check if there is 12v on the brown and white/brown spades and
connectors when turning the key to crank, then check the white/brown
connector and spade on the solenoid. If it's a 74 1/2 i.e. rubber bumper
check you don't have the white/brown and white/light-green wires on the
solenoid the wrong way round.
For the tach try disconnecting the white/blacks from the coil -ve. If the
tach still pegs there is either a problem with the 12v and ground supplies
to it on the green and black, or the electronics are faulty. If it only
pegs with the white/blacks connected to the coil, and you have electronic
ignition, then there is probably something wrong with the module connections
or the module itself. If points then disconnect the points and if it still
happens it is something to do with the coil or the connections to it. If
not then something in the distributor, check the connections including the
points ground wire.
PaulH.
----- Original Message -----
> The first is that the solenoid appears to activate (clicking)
> when the key is turned to the "start" position, but the engine does not
> turn
> over. For that one, I'm advising him to check the battery connections,
> both
> at the starter end and at the battery end. The other symptom is a little
> unusual - when he turns the ignition to the "on" position, the tachometer
> jumps to ~3000 rpm and stays there.
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