starter/ignition problems

[Deleted]

I've recently got a baffling problem with my P5B. With a fully charged battery, and no previous problems with the starter, when I turn the key to start position the ignition light dims to almost nothing and there's a strange buzzing sound coming from around the back of the tool tray or behind the heater. Is there some kind of junction box in that area that could be shorting out? Obviously the engine doesn't turn.
Any ideas appreciated

Oliver

[Baldrick]

The stater motor is on the other side of the bulkhead and possible the noise you are hearing is the soloid buzzing.

However, here is my experience with dodgey batteries lately

I had problems recently on my karmann ghiawhich i thought was the alternator and it tuned out to be the battery - having checked everything else on the car first. The dud battery showed 12.4v at rest and started the engine fine but only alternator only produced 12.7v engine running, so suggested an alternator problem as opposed to a battery problem...New battery, problem gone.

I also had ignition problems on my 2004 yamaha last year. All soorts of misfiring - Turned out to be the battery. new battery, problem gone.

I currently have a new alternator in the P5B. I get 14.8v at the alternator and only 12.7v at the battery. i also have an Ammeter that dances all over the place occasionally - the main reason i started having a prod around. The voltage drop would suggest possible a continuity problem on the wire from the alternator to the baterry via the starter solonoid, but based on much recent experience, i am going to take the new battery out of the Karmann and stick it in the Rover, as it doesnt involve getting dirty and can be done quickly! If it solves the problem, i will buy a second new battery. If it doesnt i will check the wiring and voltage along the alternator charge wire and the main battery cable.

My advice to you, swap in a good battery and see what happens. A battery can show 12.4v but might only have 50 cranking amps left in it. The solonoid might ne buzzing because it is sick, or because the lack of oomph in the battery can only make it buzz....

hope this helps

[Warwick]

A buzzing sound sounds more like a relay to me. The starter motor solenoid usually sounds more like a heavy clatter.
The reason the solenoid does this is because it is reasonably heavy and it moves (its stroke) over a reasonable distance to engage the starter's pinion gear with the flywheel ring gear. The ignition key in the start position energizes the solenoid, which moves the gear into position and then switches on the starter motor.

The starter motor draws a lot of current and this puts a heavy load on the battery. If the battery is not charged sufficiently or is old and tired, it can't deliver the required current and its voltage drops. The voltage can drop low enough that it isn't sufficient to keep the solenoid energized, so it disengages. Upon disengaging it disconnects the starter motor from the battery so battery voltage goes up again. Because you still have the ignition key turned, the solenoid is re-energized and engages the gear and powers up the starter motor again causing the voltage to drop again. This cycle keeps being repeated until you release the key or the battery succumbs completely.
The clattering noise is the solenoind moving in and out rapidly, but it is more of a heavy clatter than a buzzing sound.

[Deleted]

Thanks for your replies, I took the advice to put a decent battery on and it turned over perfectly. What confused me was my battery showed 12.8V and turned over fine one minute and then then went completely dead with the symptoms I described, without even enough power to make the solenoid click. This must have been a battery about to die.

[Baldrick]

Batteries are a bit mischevious like that - 12.8v doesnt really mean anything unless there is a load on the battery.

On my similar issue mentioned above, i put my good (new ) battery into the ROver this morning. Took a lot of cranking and "quick start" sprayed into the airbox, but that is due to fuel/igniton issues... When the engine is running i had 14.6v at the alternator, but ammeter showing negative and the battery had drained to 10.7 after 30 min of idle and adjusting mixture/timing. So i think the cable from the alternator to the starter is dodgey and not putting the juice into the system. Will check later.

Glad you are sorted. ;D

[Warwick]

There is some general battery related stuff here that may be helpful.

roverp5.proboards.com/index.cgi?action=display&board=Rover33&thread=3524&page=1

[Baldrick]

Sorted my problem - crack in the coil plastic shroud around the ht lead. Put in the coil I removed last year and it all works fine.