33 replies to this topic

[westlin]

Ok so I'm not looking for a resistor, that's good. Next one is does it gave to be a specific coil and could this be the issue or am a chasing a different issue

[dklawson]

OK... so now we know you have a ballast ignition.

 

You said the 12V supply was good.  Where is the ignition module's red wire connected?  With a ballast ignition system it must not be to coil (+), it must be to a white wire circuit at the fuse box.  

 

Now for the coil.  Unless you or a previous owner has changed the coil, the one you have will be a ballast coil.  They have a nominal low-tension resistance (across the small terminals) of 1 to 2 Ohms with the wires removed.  If you put a "standard" 3 Ohm coil in the wiring circuit for a ballast coil your engine will have a very weak spark.  Don't buy a new coil until you answer the question about where the module's red wire is connected.

[westlin]

From memory red per the power spark instructions is to the coil but let me check when I get home. Coil has been changed to a lucas (prior to me buying the car) I've not checked model number if it's on the coil.

[westlin]

Just checked their website (link below) and states red to positive and black to negative. Didn't think I was going mad

http://www.simonbbc...._1275_1300_1380

[dklawson]

Regardless of what the instructions tell you, electronic ignition modules were designed to run on full 12V.  You do not have that with a ballast coil and a red wire connection made to coil (+).

 

I anticipate that you will say "I connected my meter between coil (+) and earth, cut on the ignition, and measured 12V so the wiring is OK".  There is a flaw with that test.  The ballast resistor only drops the voltage when current is flowing.  That only happens when the points are closed (or the electronic module is conducting).  A simple meter test without an additional step will give you a false voltage reading.

 

Repeat your voltage test as follows.  Connect a jumper wire between coil (-) and earth.  Connect your meter between coil (+) and earth and set it to measure volts.  Turn on the ignition.  With your ballast wiring (pinkish and white/yellow wires on coil (+)) you should find the voltage is now somewhere between 6V and 9V.  That's because current is flowing through the circuit and the ballast wire is doing its job... dropping the coil voltage.  Remove the jumper when you are done with the test.

 

Powerspark may not make a big deal out of this but others such as Pertonix (the ignitor module) and Lumenition do.  You cannot supply a bit of electronics with 2/3 to 1/2 of the necessary supply voltage and then expect it to work properly.

 

Before you spend any money on new components, move the ignition module's red wire to a switched 12V white wire connection at the fuse box and see if the tach works better/properly.  This is a quick thing to do that will be both better for the ignition module and may resolve the tachometer problem.

[westlin]

Is w/y not a 12v supply from the ignition switch

[dklawson]

The white/yellow is the bypass wire coming from the starter solenoid.  It supplies power to the coil while you are turning the engine over on the starter motor.  Its purpose is to deliver higher voltage to the coil for starting the engine.  During normal running the pinkish wire supplies power to the coil (+) terminal.  

 

The pinkish wire is not a regular wire, it is a resistance wire adding about 1.5 Ohms inline (series) resistance to the coil.  The pinkish wire is typically spliced to a white wire leaving the ignition switch.  That's why a connection of the electronic ignition's red wire to coil (+) on a ballast ignition system results in a module running below its specified voltage.

[westlin]

Doug

I wish I could shake your hand. Ive checked the voltage on the positive side of the coil, just uder 6 volts (my original voltage check was at the gauge end not coil), then run a cable to the fuse box for a direct feed, on initial tests show the rev gauge is behaving but as its now18.30 in the uk I dont want to annoy the neighbours so will carry out a further check tomorrow.

Ill update after a further check tomorrow, but looks good at the moment

thanks again

Stephen

[westlin]

Doug

ran the car up today and rev counter nice and stable. Thanks again

[dklawson]

That is great news!  Thanks for posting what worked for your car.  It is good to have conclusions to troubleshooting threads.

[Pairaminis]

So does this mean that a rev counter used with a points distributor and ballast coil with be erratic?

Jack

[dklawson]

So does this mean that a rev counter used with a points distributor and ballast coil with be erratic?

 

Not at all.  What it means is that if you are using an aftermarket electronic ignition module on a car with a ballast ignition system, you need to wire the power for the ignition module to a full 12V source. 

 

The tach Westlin was having issues with was only displaying what was going on with the signals it got from the coil.  Those signals were erratic because the ignition module was not running on full power.

[leadly]

Doug strikes again!

[westlin]

Some bad news, although with car running on the drive the rev counter behaved out on the road yesterday it was back to bouncing all over the place again.

[dklawson]

There are two or three possibilities.  

 

The first possibility is that the tach is old and parts are failing.  That typically means replacement or professional repair.

The second possibility is that your ignition coil is failing.  Before you buy a new coil, see if you can borrow one from a friend and give that a try.  Over here, electrical parts like coils cannot be returned and they are not cheap so you only want to buy one if you have to.