Hi there,

 

I've got a 1981 KE38 that I'm currently using as a daily. Its a stock 4KC and 5 Speed with the standard Carby and Bosch ignition. It was running fine for the past month and when I went to go for a drive on the weekend it wouldn't start, it only turned over. my father and I diagnosed the problem to be an electrical fault between the coil and the spark plugs. we have swapped out the coil, plug leads and distributor cap but haven't had any luck getting it running. The problem is something to do with the coil, as we have replaced it and there is no spark between the coil and the dizzy. We have checked voltages and get 11.8 volts at the ballast resistor and 8 volts at the coil. We now suspect that Condenser or the ballast resistor may be bad.

 

My Question is has anyone had the same or similar problem that would be able to help me out? Any help would be great thanks!

 

Thanks in advance

You can rule out the ballast resistor! Theres another wire to the coil + which supplies a full 12v when cranking and bypasses the ballast resistor. ...and in saying that it gives you another important thing to check.

I'm a newbie to Corollas as well and Dad and I are just going off what we know from working on Old Holdens!

Did you put the coil wires on the correct posts?

That'll get you every time.

engine earth wire is probably shot or corroded.

See if u get a spark across to the battery negative instead of to the dizzy.

Edited April 15, 201610 yr by rebuilder86

Thanks rebuilder86, I did check that the engine was earthed i.e. checked it wasn't loose and looked undamaged, no electrical test though. The engine cranks so I would assume the earth is OK.

 

So far we have replaced :

- Coil

- Ignition leads

- Dizzy cap

- Rotor button

- Points

 

Checked :

- Battery Voltage (12.4V)

- Voltage at the ballast resistor (12.xV)

- Voltage the coil + (10.xV)

 

The 15 amp "engine" fuse looks solid but one of the end caps is loose.

Edited April 15, 201610 yr by Stinky

As I eluded to earlier have you checked voltage at the coil while cranking to make sure the 12v start circuit isn't dead?

Thanks Taz_Rx, missed that, will try it out tonight. If we are not getting 12V, what do we need to be looking at to fix?

We have 7.9 volts with the ignition on and 9.7 volts while turning the car over, this is at the negative of the battery and positive of the coil. Is this good or bad?

Edited April 15, 201610 yr by Stankman

We have checked voltages and get 11.8 volts at the ballast resistor and 8 volts at the coil. We now suspect that Condenser or the ballast resistor may be bad.

 

That is what it should be, the ballast resistor knocks the 12V down to 9V so the 9V coil can run all day. You should get that 9V at coil +ve with the ignition turned on.

 

When you turn the key to crank another wire bypasses the resistor and takes ignition 12V straight to the coil +ve. You only get 9V anyway because of the current drain of the starter motor. So your last post is correct, the coil gets 9V cranking and 'running'.

 

So the ballast resistor is OK, but the condensor should have been one of the first things to change. Bad leads give odd misfires, the coil you can check with a multimeter, and the dizzy cap you can spray with WD40 to overcome most cracks.

 

If you use a multimeter on 'ohms' you should get no circuit from the coil -ve to earth when the points are open, and a circuit of an ohm or two when the points are closed. This is with the ignition off, the tacho wire taken off the coil, and you turn the motor with a spanner. That will tell you if the points are opening and closing and carrying electricity. There could be a broken wire inside the dizzy, it is unusual for all spark to vanish at once.

 

Wiring diagram is here if you need one-

 

https://www.dropbox.com/s/s0xs2udvrv9qfl2/downloadfile.jpg?dl=0

If you use a multimeter on 'ohms' you should get no circuit from the coil -ve to earth when the points are open

 

We got 6 ohms :/

aaaand just replaced the condenser, no effect :(

Tried running a new wire straight from the dizzy to coil -ve and bypass the loom? Couldn be coil isn't being fired at all!

Tried running a new wire straight from the dizzy to coil -ve and bypass the loom? Couldn be coil isn't being fired at all!

 

Just did, again no joy :(

We got 6 ohms :/

 

Seems like your problem is there. So that is taking the dizzy wire off the coil -ve and running your multimeter down the coil wire and across to earth. Which means the power is shorting out when the points are open

 

Which means you have broken points that are shorting out, or a broken wire that is shorting out, or a condenser that is shorting out, or the points wiring assembled incorrectly so it shorts out or...

 

With points open that coil-ve wire shouldn't go to earth.

Edited April 16, 201610 yr by altezzaclub