Auto electrical expert wanted

[V8 Rumbler]

I remember bringing this up last year and have done nothing about it:?

I do not get 12v on the +ve side of my coil whilst cranking. The wire which goes down to the solenoid is in tact but is not getting that 12v signal. My car starts fine in the summer but takes longer in the winter and this is why.

All I need is to get a 12v feed to my coil whilst cranking so can anyone provide an 'idiots' guide on doing this please. There is clearly something wrong with the solenoid but I am after a simple and cheaper fix than replacing that.

I have been speaking to another Stag owner with a similar problem - he has the high torque starter fitted , which after looking back on old posts, do not have the cold start wire so how do the high torque starter guys solve this?



Darren

[Barry Brown]

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Hi Darren
I was told by a ex Leyland guy that the reason for the ballast resistor and the starter short was to extend the life of the points and dizzy cap.
I also have a high torque starter and have not got round to putting in the shorting mod, though since I have been running the car all winter and not had any problems I might not bother.
If you have electronic ignition then the spark should be adequate even on cold days so long as the engine turns fast enough.
The modification to put the short back on is to get a relay and power the coil from the starter feed; then take a live feed to the common terminal and connect the normally open contact to the plus on the coil, this shorts out the ballast resistor.

hope this helps

Barry

[V8 Rumbler]

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Hi Barry
Yes I do have electronic ignition. I just need a little more info on the type of relay, where to fit it and which wire to break into and where?

I would have thought that we could all benefit from a stronger spark during starting!- particular during cold weather

Darren

[PaulW]

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Remember when cranking a cold engine unlikely to get 12v due to load on system. Get someone to crank over engine will you measure directly across battery at least you know what you starting voltage is .. you may be surprised.

PaulW

[V8 Rumbler]

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PaulW wrote:

Remember when cranking a cold engine unlikely to get 12v due to load on system. Get someone to crank over engine will you measure directly across battery at least you know what you starting voltage is .. you may be surprised.

PaulW

I Paul

I have checked it all out and the 12v that should be winging along the wire from the solenoid is not there.

[Barry Brown]

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Hi Darren
I will send you a spec. for the relay and which colour wires to break into as soon as I can.
I haven't got the stag here at the moment so I can't peer in the bonnet at present. I will look up the manual to check the colours and positions. The relay will be a standard one from Halfords and the like.

contact you soon
Barry

[PaulW]

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according to book you should have a fattish white/red wire going to s/motor from ignition switch to get starter motor turning and a smaller white/orange wire going from starter motor to coil plus, this should be at you cranking voltage. When engine fires you release ignition key back to normal position this stops s/motor disconnectsfeed to coil and thereafter coil runs via ballest resistor.

cannot see a reason not to connect o/w direct to r/white wire to get you 12v back round to coil this will be disconnected once starter motor is switched off.

Hope this makes some sense !

PaulW

[V Mad]

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PaulW wrote:

cannot see a reason not to connect o/w direct to r/white wire to get you 12v back round to coil this will be disconnected once starter motor is switched off.

Hope this makes some sense !

PaulW

No you should not do that because the solenoid will remain permanently connected to the coil circuit; this will rob the coil of voltage/current.

The solenoid should be putting out a 12v signal on the appropriate terminal, but if this is not working you can use a relay instead. Just connect the relay coil to the cranking supply (R/W), then the contacts shouldbe used to supply a full 12 volts to the coil. That way nothing is else isleft connected to the coil +

[V8 Rumbler]

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V Mad wrote:

PaulW wrote:

cannot see a reason not to connect o/w direct to r/white wire to get you 12v back round to coil this will be disconnected once starter motor is switched off.

Hope this makes some sense !

PaulW

No you should not do that because the solenoid will remain permanently connected to the coil circuit; this will rob the coil of voltage/current.

The solenoid should be putting out a 12v signal on the appropriate terminal, but if this is not working you can use a relay instead. Just connect the relay coil to the cranking supply (R/W), then the contacts shouldbe used to supply a full 12 volts to the coil. That way nothing is else isleft connected to the coil +

So where should I pick up the cranking supply wire? What is the purpose of the relay? & what sort of relay do i need?

Darren

[V Mad]

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just a standard (single pole n/o)30A auto relay (eg Maplins) will be fine. You can pick up on the r/w wire fromwherever is most convenient (ignition switch, solenoid etc).The relay is necessary in order to provide a proper isolated switched 12volt supply.

[PaulW]

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Yep see what you mean brain in Friday mode, relay should provide osolated coil supply same as stater motor would should it be working correctly

PaulW

[Barry Brown]

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Hi Paul
I see other have pointed out the secondary circuit.
I was thinking that it would be possible to use the idea by using a diode to stop the feed via the coil to the starter.
It would have the advantage of being able to be put it the starter to coil wire.
The only disadvantage is that a diode has a forward voltage drop of 1.2 volts so the boost would only be 10.8v not 12v.
I might try it to see if it has any merit.

Barry

[V8 Rumbler]

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V Mad wrote:

just a standard (single pole n/o)30A auto relay (eg Maplins) will be fine. You can pick up on the r/w wire fromwherever is most convenient (ignition switch, solenoid etc).The relay is necessary in order to provide a proper isolated switched 12volt supply.

Thanks Chris
You are dealing with a real novice here--sorry

So I can pick up up red/white wire going to the solenoid-I understand that bit,

Darren but how many terminals should the relay have and what do I connect the rest to?:?

Darren

[Ferds]

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All,

I just wanted to clarify the following:-

The ballast resistor is there for when the car is running and you will only get 6v at the coil (or at least a reduced voltage).

Please note:- On early cars, this can be seen as a white block connected to the coil. On later cars a 'white with pink stripe wire' with a high internal resistance, runs behind the dash, out to the engine bay and to the coil.

Okay... there should be a 'bypass wire' (i.i.r.c) which runs from the ignition switch - or the supply to the starter solenoid. This is also connected to the +ve side of the coil.

However, as this becomes live when the engine is being started (cranked over), you are unlikely to see 12v at the coil, but it does allow more volts to be delivered to the coil. If it is not working, only the resisted 6v is available at the coil, and as the engine is cranked over, this will drop to about 4v - which is where you will experience poor starting.

Hope this helps.

Chris