Cold starting

[Barry Townsend]

My 1931 RN refuses to start from cold using the starter motor

It turns over OK on the starter but refuses to fire but starts easily first time if I swing it. 

Therafter it's 'on the button' every time.

I'm assuming that because as it's still 6v the coil is being partially starved when using the starter. I've fitted a voltmeter which seems to confirm this The battery is in good condition.

I don't want to change to 12v - what are the alternatives?

[John Cornforth]

Hi Barry

A 6 volt car should start fine - they all did when they were new !

If your voltmeter is telling you that the battery terminal volts are dropping too low, then it's time for a new battery.

Alternatively if the battery is reasonably healthy you may have a connection somewhere that is a bit below par and causing the coil voltage to be less than required.

With early cars, the earth return from the starter motor was via the engine block, then via the crankcase mounting feet to the chassis, then from the chassis to the body via any fixing bolts, then via cable from the body back to battery negative. All a bit torturous, and any volt drop in this path will also reduce the coil voltage. If you haven't already, try an earth strap direct from the starter body to the battery. Even a single borrowed jump start lead from starter to battery might be worth trying to see if it makes any difference.

If you want to be more scientific, wire your voltmeter between engine block and battery negative post. If you see any voltage drop more than about 0.2 volts when cranking it's a sign that the earth return path is not really good enough.


See wiring diagrams for all years here: http://www.da7c.co.uk/technical_torque_a...Wiring.pdf

[colina]

My brother and I once had a TR4A that developed a similar problem some time after restoration. After the choke cable started smoking I discovered the problem - I had forgotten to fit the crankcase to chassis strap and therefore the current return was via the outer of the choke cable where it went through the bulkhead as it was also missing the rubber grommet! It worked ok for a while until the choke cable was fully cooked!

So definitely check the battery cables and, as has been said, check ignition voltage whilst cranking.

[andrew34ruby]

My 1931 RN refuses to start from cold using the starter motor

It turns over OK on the starter but refuses to fire but starts easily first time if I swing it. 

Therafter it's 'on the button' every time.

I'm assuming that because as it's still 6v the coil is being partially starved when using the starter. I've fitted a voltmeter which seems to confirm this The battery is in good condition.

I don't want to change to 12v - what are the alternatives?

Another alternative is to feed the coil from a separate battery. Main battery to feed the starter motor and another battery to feed the coil.

[Reckless Rat]

If the battery is good, and the starter motor in order then there should be no problem starting from cold on 6v. However I would recommend a separate earth cable direct from the battery to the starter motor to ensure that the starter motor is getting all it needs. There should then be sufficient residual current to satisfactorily energise the coil during cranking.

[Howard Wright]

Hi Barry

You may also want to clean up the starter switch, which I think on your car is a push switch on the passenger side of the tunnel.

The terminals can become loose and the internals full of crud.

Cheers

Howard

[Robert Foreman]

A quick test is to use a jump lead from the earth side of the battery directly to the crankcase. If it starts easily then run a separate earth underneath to one of the bellhousing studs in a heavy gauge cable.

[Ruairidh Dunford]

What Robert said - exactly what I would do.