Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing 4/4 Starting problem.

Morgan 4/4 starting problem.

I am having problems starting my 1994 4/4 Zetec 1800 Silver top engine. The battery is in good condition and holds its charge.

When attempting to start the engine it just goes ‘whrrr as if a flat battery’ and the battery indication on the dashboard drops to around 5 Volts. When the ignition is turned off the battery indicates normal level.

My measurements with the ignition OFF is 13.4V, with ignition ON is 12.5V and the measurement at the input to the starter motor is 12.4V. This indicates a voltage drop of 0.1V down the length of the cable from the rear to the front. Is this voltage drop acceptable? When turning the engine over the voltage at the starter motor input drops to 6V.

The vehicle can be started by directly putting 12V onto the starter motor input. The engine then fires up first time.

I hope it is not the voltage drop/resistance along the cable causing this as it does not look an easy job to replace.

Has any member any ideas on this problem. Thanks in anticipation.

Peter Hardy

RichV6 is your man, but a battery can appear to have a good voltage and then drop massively while under load. Have you tried a jump start from another battery? That would determine if the battery is OK.

Thanks for the reply. I have not tried another battery but will find a suitable donor one to try. While I say the existing battery is good is that my C-TEK charger indicates all is good but I do not know how that can be case with no heavy load test.

Check / clean all the earth connections (battery to chassis, engine block to chassis) too Peter. Quite common for a high resistance on that side to show up when high current is demanded e.g. for starting. Good luck!

If it is agell battery they can sow as fine but under load fail. I had the same on my CX.
How did you put 12v directly onto the starter? Whas it the same battery?
It could be also a poor earth. They may look good but disconnect & clean them.

Two possibilities Peter.

1) The battery capacity has reduced to a tiny fraction of original through normal ageing, such that your charging system easly keeps it fully charged but only within the confines of its much reduced capacity. This allows it to show a normal voltage reading when ignition first turned on, but dropping to almost nothing when starter is asked to operate as the current demand can't be supported.

2) You have a high resistance connection on the battery lead to starter or battery negative leads to chassis/chassis to engine block.

I would immediately suspect the former if battery a few years old but no harm checking the battery connections for corrosion.

Note the volt drop you measured at the starter motor when its not operating is irrelevant until the starter is operating!

You could check the voltage at the battery terminal when cranking the starter ... if it drops to 6v like the starter input then it's the battery but if it stays up around 12v it's likely a bad connection issue in one of the heavy cables to the starter

K

You don't say how old the battery is, there will be a manufacturers date code (usually hot stamped) on the top

Some batteries have the month and year stamped on top of one of the terminals..

Sorry I disagree with that second statement K, if I've understood correctly. Note also the OP has already stated the voltage measured at starter motor whilst it's operating is 6 volts.

If however the voltage measured under same circumstances is in the order of 11 to 12 volts everything would be normal. It certainly wouldn't indicate a faulty battery cable connection.

The measured 6 volts at starter could be down to battery itself temporarily not being able to maintain a higher voltage due to the attempted current draw from its limited capacity. It could also be caused by severe volt drop at the point of a poor battery cable connection though with attendant local heat, and with similar results regarding starter operation.

As mentioned above I favour the battery being at fault almost irrespective of it's age, particularly as OP mentioned dash voltmeter dropping to 5 volts (likely a little pessimistic) whilst starter operating. This suggesting minimal voltage drop on battery cable run.