Thread: Power in coil none coming out

All I can help you withis the basics, not sure of the Landy componant

+ terminal on coil to ignition, some have ballast resister by passed on cranking.
- terminal on coil to the distributer,

The distributer compleates the earth cucuit so + on both sides does happen.


Is it points or electronic?
I have herd the crank angle sensor in the bell housing can play up.

which engine? theres a few things that can cause this.

if its a series engine check the capacitor and the points.

the fact that the coil is throwing A spark means its ok.

try this.

bridge a 20ishwatt 12v light across the connections to the coil after you disconnect them from the coil turn the engine over slowly by hand with the ignition turned on it should blink at you.

while the coil is disconnected attach the 12v light to the coil terminals apply an earth connection then put a plug lead with a plug in it onto the HT side on it and earth the plug. apply 12v+ directly to the coil, the light will light, remove the 12v and the plug should spark.

theres the first step in fault finding a coil

If you have a meter the HT side should read about .4-.6 ohms and the LT side lots of ohms

Originally Posted by Mudsloth

Howdy everyone, I have 98 3.9 disco, I had the rings and bearings done and once the motor was put back in I suddenly have no spark, well the car has no spark my spark is fine. The coil has power but isn't sending anything to the dizzy. When the ignition is turned on it gives a single spark but when cranking there is nothing. Have tried a different coil but no difference. I'm thinking the mechanic has stuffed up the wiring somehow as both the positive and negative sides of the coil are showing power, i.e. a multimeter will read positive power on both sides. If anyone has had this problem please let me know, also if someone could post a pic showing the wiring of their coil, the top of the coil, that would good as I'm sure they have managed to plug an extra wire into it. These guys are great mechanics but lousy auto elecs.

You will find there is 12 volts on both sides of the coil because there is no load on the coil when it is stationary. The ignition amp should have 2 wires going to the coil, one to positive and one to negative. The negative wire is the one that switches the coil to provide spark. The ignition amp knows when to fire the coil by the red and blue wires from the distributor via a shielded cable. Make sure this cable is connected at the dissy and the amp. There will also be a white/black stripe wire that must be connected to the ignition coil negative. This is for the ECU to detect firing pulses. The car won't run without it.

My picture is of a Bosch ignition amp conversion I fit to most D1's that come near me. The wires you need are clearly visible here as they go to the Lucas amp in the same general position. The coil +ve is to the right of the picture.

Try here

It is the change in current that generates the big voltage for the spark. The points or electronic ignition switch the coil to ground (ON or zero volts at dizzy side of coil) causing current to run through the coil, when the points open, the current through the points goes to zero in a very short time (fast change in current) causing the High Tension (High Voltage ) spark. If both sides of your coil are at the same voltage it may not be a problem as the dizzy might just be in an open circuit position. You have to turn the engine slowly by hand and the dizzy side of the coil should be going zero volts and then back to 12 v at which time you will get a spark. If this is not happening (going 0 V, 12 V, 0 V, 12 V) most likely your points/electronic ignition are open circuit all the time.

Way to check if your coil is working is take the side of the coil going to the distributor to ground and then open it shortly after that, you should get a spark off the high voltage ignition lead coming from the coil.

As blacknight said if your coil is throwing a spark when you turn the ignition switch on and off then your coil sounds like it is alive/ok.

Originally Posted by Mudsloth

I have 98 3.9 disco,

This engine, guys. It's electronic ignition. Don't go shorting the negative side of the coil to ground, it's unhealthy for electronic coils.

its not bad for the coil its bad for other things. thats why you disconnect the coil first

running the coil independant of the electronic ignition is harmless unless you get careless with where you attach your earths or let the spark jump to.

Originally Posted by bee utey

This engine, guys. It's electronic ignition. Don't go shorting the negative side of the coil to ground, it's unhealthy for electronic coils.

Why? how do electronic coils differ from others?

I think the only thing that has changed with coils over the years is that they introduced a ballast resistor. And that is bypassed when your cranking on the starter anyway.

Not good to test electronic coils while all wired up in the car.
Trigering them with the earth method usualy results in the distributor pickups getting damaged.