That old hot start thing
Discussion
I'd heard of this before but never been affected by it - until yesterday.
Took the Griff out for an Autumn blast, parked up for a minute and then went to start... fuel pump primed as usual - turn key the rest of the way - nothing. Not even a click.
Was pondering exactly how to get home when I recalled the hot start issue, so opened the bonnet and waited. After about 10 minutes it started OK.
I hear the problem is caused by hot wiring failing to conduct enough current. If so, is there something I can tighten up under the bonnet or is a better fix to be had?
Took the Griff out for an Autumn blast, parked up for a minute and then went to start... fuel pump primed as usual - turn key the rest of the way - nothing. Not even a click.
Was pondering exactly how to get home when I recalled the hot start issue, so opened the bonnet and waited. After about 10 minutes it started OK.
I hear the problem is caused by hot wiring failing to conduct enough current. If so, is there something I can tighten up under the bonnet or is a better fix to be had?
This is a good thread which explains things. Its not just the cables but more of an immobiliser issue.
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Simpo Two said:
Thanks. Hmm, complicated. I suppose being a Griff the 'long battery lead' issue is removed as the battery's in the passenger footwell?
The 'remote plipper' part of the immobiliser packed up years ago but the 'stick it in the slot and wiggle' part is/was fine.
1997 500 BTW.
Nope. Battery is in the same place for Griff and Chim.The 'remote plipper' part of the immobiliser packed up years ago but the 'stick it in the slot and wiggle' part is/was fine.
1997 500 BTW.
The starter motor has a thick power cable which comes directly from the battery and an earth connection via the engine, we will assume these are OK otherwise you would have additional symptoms.
When you turn the key a contact in the ignition switch connects 12v to a cable which goes to a solenoid mounted on the side of the starter, when that pulls in it closes a switch which connects the +12v from the thick cable to the motor.
Mostly the problem arises because the cable from the switch to the solenoid goes via one of the immobiliser channels which are a bit rubbish and have a habit of becoming faulty. Simply bypassing the immobiliser channel by taking a cable directly from the switch to the rear of the starter solenoid is simple and quick fix, It is still not ideal however. The current drawn by the solenoid is rather more than idea for the ignition switch and in an ideal world the solenoid supply would be switched by a relay.
Having said all that the motor/solenoid combination is in a rather harsh environment and can develop a similar symptom when hot. Much better high torque lower current starters are now available if that is the problem.
To work out which is causing the problem connect a cable to the solenoid drive and bring it back into the cabin with a volt meter attached. Get the fault to occur and see if the switched supply is lot less than 12v when you turn the key if it is the voltage is getting lost between the ignition stitch and the solenoid, most probably in the immobiliser. If there is a good robust 12v and nothing happens it is probably time to change the motor or if you are so inclined take it apart and fix it.
When you turn the key a contact in the ignition switch connects 12v to a cable which goes to a solenoid mounted on the side of the starter, when that pulls in it closes a switch which connects the +12v from the thick cable to the motor.
Mostly the problem arises because the cable from the switch to the solenoid goes via one of the immobiliser channels which are a bit rubbish and have a habit of becoming faulty. Simply bypassing the immobiliser channel by taking a cable directly from the switch to the rear of the starter solenoid is simple and quick fix, It is still not ideal however. The current drawn by the solenoid is rather more than idea for the ignition switch and in an ideal world the solenoid supply would be switched by a relay.
Having said all that the motor/solenoid combination is in a rather harsh environment and can develop a similar symptom when hot. Much better high torque lower current starters are now available if that is the problem.
To work out which is causing the problem connect a cable to the solenoid drive and bring it back into the cabin with a volt meter attached. Get the fault to occur and see if the switched supply is lot less than 12v when you turn the key if it is the voltage is getting lost between the ignition stitch and the solenoid, most probably in the immobiliser. If there is a good robust 12v and nothing happens it is probably time to change the motor or if you are so inclined take it apart and fix it.
steve-V8s said:
To work out which is causing the problem connect a cable to the solenoid drive and bring it back into the cabin with a volt meter attached. Get the fault to occur and see if the switched supply is lot less than 12v when you turn the key if it is the voltage is getting lost between the ignition stitch and the solenoid, most probably in the immobiliser. If there is a good robust 12v and nothing happens it is probably time to change the motor or if you are so inclined take it apart and fix it.
Agreed, this is the best way to find out what is going on. If you do get a voltage drop at the solenoid you can then trace it further back to determine precisely where the problem is (or isn't!), although that does mean digging around in the harness it will give a more precise answer.
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