intermittent starting problems, alternator or starter

[dennisthemennis.co.uk]

Hi.

I have a defender 200tdi and have had it for 4 years replacing the starter motor twice, both times I could start it with a tow start so my guess was right, however this time with a similar situation although sometimes it starts and sometimes it does not.

My question is if it is the alternator and not the starter would the engine try to start or would it just be dead as if the starter had gone? The battery is only 12 months old and is fully charged.

thanks dennis

[crwoody]

A faulty alternator on it's own would not prevent the engine from starting, it would however result in a discharged battery which of course would prevent starting.

Perhaps you have a bad/loose connection on an earth lead from the chassis to engine, this could give the appearance of a faulty starter motor.

[dennisthemennis.co.uk]

A faulty alternator on it's own would not prevent the engine from starting, it would however result in a discharged battery which of course would prevent starting.

Perhaps you have a bad/loose connection on an earth lead from the chassis to engine, this could give the appearance of a faulty starter motor.

thanks that is quite helpful.

I should have checked all the leads before I bought a new starter motor as the lead that connects to the ?solenoid? was loose and was the intermittent thing.

[Guest]

Sorry, but could it be the Battery?

[g90]

Perhaps you have a bad/loose connection on an earth lead from the chassis to engine, this could give the appearance of a faulty starter motor.

ditto. Have had 2 problems with not starting. check ALL leads and connections, batt terminals crusty in my case. also pull the trigger wire off the solenoid an make sure thats also clean.

[isuzu110]

Check the voltage to the solenoid on the starter motor. I was only getting 9v which was enough to make the solenoid click, but not actually engage. Solved that by adding a relay into the circuit. The 9v is enough to switch the relay, which in turn switches a full 12V to the solenoid.

Also check the ignition switch. They are not the most reliable part.

[errol209]

Check the voltage to the solenoid on the starter motor. I was only getting 9v which was enough to make the solenoid click, but not actually engage. Solved that by adding a relay into the circuit. The 9v is enough to switch the relay, which in turn switches a full 12V to the solenoid.

Also check the ignition switch. They are not the most reliable part.

To add to the above (though adding a relay is working round the problem rather than fixing it ...) The ends of the wires to the solenoid can get hot and crusty (near the exhaust) so running a multimeter round might help locate the problem. The main starter circuit includes the battery, main battery cable, solenoid and the big earth strap from gearbox to battery, and the solenoid circuit has the ignition switch and one wire (brown/yellow IIRC) to the solenoid coil - all relatively straightforward. The earth strap and connections is always first suspect, as the symptoms only manifest under high current drain (sometimes as the infamous burning handbrake cable fault).

If it fires OK 99/100 and then doesn't once, it could be that you have a grotty / dead sector on the commutator of the starter motor.

[Andrew Chua]

don't rule out the battery. i've gotten a faulty optima yellow top before and for a good 4 months i was trying to figure out if i had a parasite drain in the circuits.

on some days it started fine on some days after sitting for 20hrs, will refuse to start. the battery would charge enough to crank over if left sitting for 14hrs at most. until one day when i parked it up for 14 days, the battery could not be charged and even with a c-tek 7000 charger which is a 8 stage charger. it indicated charged but would drop to 10v immediately when disconnected.

That was not the end of it, during that period at the battery had problems charging, the alternator ran at 100% duty cycle and hence it burnt out, further adding to the problem which had me really confused over where the real problem was.

interestingly there were times when the voltage read 13.3v when the engine was not running, immediately after a ignition off.