coil wiring

I checked the voltage to my coil today and got 5.6 volts with the ignition on.

When I turned the key to crank the starter the voltage stayed around 5.6 volts. Is this normal ?

1. Should I get a full 12 volts at the coil when the motor is being cranked ?.

2.I dont see a pink wire going to the coil, I have a red wire with a green trace that goes from the coil into the firewall plug.

Nothing is cut or spliced.

3. What happens on the interior side of the firewall, is the pink wire inside the car ?

Thanks

Thanks Jim

I will do some checking tomorrow.

I think I know why I did not the 12v when cranking as I pulled the rear thin wire on the solenoid to stop the starter when I did the voltage test, so that probably explains that one as I did not realise it would also be supplying the coil 12v.

If I am only getting a low voltage at the coil does it mean that the pink wire has gone bad ? do they do that ?

Thanks

Mark

Have done some checking today.

Found the pink wire. Feed comes from my ignition switch to a plug under the dash, the rally pac tach then plugs into this then the pink wire plugs into the other lead coming out of the tach and goes to the firewall plug.

I have 12v going into and out of the tach.

If I pull the coil feed wire and connect a meter between it and earth I have full 12v.

If I put a meter across both coil posts with both wires on I have 5.5 - 6v.

If I do this with the engine running I only see 4-5v.

I have 10v across the coil posts when the motor is being cranked.

I have tried 2 coils the readings are the same.

I am no auto electrician so please tell me what I am missing. As Jim says I should be seeing 8-9v across the coil.

Thanks

Dave

I remember when I first got the car I was concerned that according to the label on the coil it was a 12v coil not intended to be ballasted. So I bought a coil designed to be ballasted and did some checks at the time to determine whether the wiring was stock or not and never really got to the bottom of it.

So I am re visiting the issue and thanks to Jims tips I have found that I still have the proper set up but am confused as to why the voltage at the coil is so low.

To answer your question yes the car starts and runs, but ever since I have owned it trying to get a smooth idle has been tricky, I have been wondering if the coil is getting enough volts.

I seem to be a couple of volts adrift at the coil with the ignition on and also when cranking and even more volts adrift when running.

Battery voltage = 12.8v

Rear solenoid terminal when cranking = 11.7v

Voltage across coil when cranking = @ 10v

Voltage across coil with ign on = 5.5 - 6v

Voltage across coil with engine running 4 - 5v

Mark

Edited by - cobraboy on 06/13/2010 12:42:57

<BLOCKQUOTE id=quote><font size=1 face="Verdana" id=quote>quote:<hr height=1 noshade id=quote>

Low voltage is sometimes the result of corroded contacts. I know, something you really wanted to hear. Another possibility is a "pinched" wire. That being said, take a measurement from the positive terminal of the battery to the positive terminal of the coil - not to ground. This will give you the voltage drop. Do a reading at start = 2.5v

and at run. = 6.5v

Both readings taken with both wires on coil.

Start should be zero, run should be about 5 to 7 volts. What is the run voltage at the battery? = 14.4v fast idle

That should be about 14 volts.

Jim

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I have parted and cleaned all electrical connections in the engine bay and coated them all with petroleum jelly.

The firewall plugs are in very good order with no corrosion on pins or sleeves.

So am I OK with these readings

Thanks Jim

Mark<b></b><b></b><b></b><b></b><b></b><i></i><i></i><i></i><i></i><i></i><font color=red></font id=red><font color=black></font id=black>

Edited by - cobraboy on 06/13/2010 16:52:13

Thats the trouble with you Americans - cant find the answer so go and hit the bottle !!

Actually its a great idea <img src=images/icon_smile_big.gif border=0 align=middle>