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Struggling with my Nodiz on pinto
simonrh - 25/7/15 at 07:49 PM

I have had my Pinto running on Nodiz on and off for a while.

It has always started and idled nicely but wouldn't rev properly.

It runs a basic spec pinto on twin 40s and the map is only 2D for now and is as close to the curve on the stock dizzy for now as I can get it. The stock dizzy was rolling roaded at the tail end of last year and was running OK with the odd misfire (hence the change).

I traced most of the problems to the fact that the chunky plug leads I had made up basically had the rubber boots in the wrong place at the coil pack end and so you couldn't get the connections pushed on far enough. The sparks would leap from cil pack to the leads but then breakdown as the revs raised. Eased the boots along the leads until you could hear the leads terminate correctly and then off it all went. Drives really nicely.

Took the timing light, rotor arm, standard plug leads and multimeter out of the footwell and left them at home finally as all seemed to be OK and then a few days later, dead on the hard shoulder of the bedford bypass.

Driving along at 75 and then one cough and then full house misfire, the engine was still turning but it was like the timing had suddenly gone way out.

It would spit back all over the place, just about run but without even enough power to move under its own steam but that is it.

Things I have checked so far:
Voltage to ECU
Output of crank sensor (checked with oscilloscope, clean waveform and can see missing tooth)
Spark plugs (blue crackley stuff coming out the end - no idea of quality or order of firing specifically)
Nodiz software shows engine cranking on digital tacho so it is seeing the rotation (and the blue/ green lights are flashing on the unit which indicates the same thing).
Any ideas what to check next? What sort of voltage is used to fire the coil pack on the low voltage side? I want to put the oscilloscope on there but only if the voltage isn't too high.

daviep - 25/7/15 at 09:32 PM

Have you had a look to see that crank trigger or pick up haven't moved?

Have you put a timing light on it to check whether ignition timing is still correct or close?

Have you checked camshaft timing hasn't moved eg timing belt slipped?

Low tension side of coil is 12v and is grounded to collapse the magnetic field and trigger the spark from the HT side.

Cheers
Davie

snapper - 26/7/15 at 06:58 AM

I had an annoying intermittent problem similar to yours.
Untraceable until I checked VR sensor plug, the cable had broken at the pin, was in contact but only broke contact occasionally causing misfires and sometimes complete loss of spark

MikeRJ - 26/7/15 at 08:39 AM

quote:
Originally posted by simonrh
Any ideas what to check next? What sort of voltage is used to fire the coil pack on the low voltage side? I want to put the oscilloscope on there but only if the voltage isn't too high.


The coil primary voltage in a standard Kettering type ignition system is basically a divided down version of the secondary voltage e.g. if your coil had a turns ratio of 1000:1 then 20kv peak on the secondary would give 200v on the primary, which is a fairly typical peak voltage.

The the ECU will also clamp the maximum primary voltage to prevent damage to the coil driver. This clamp is usually around 300v but will vary between different ignition systems.

Ensure both your scope probe is rated for high enough voltage, many of the cheaper ones have a fairly low maximum voltage even x10 or x100 versions.

Don't ever run without a suitable spark gap in the secondary. This will produce very high secondary voltages which will both stress the coil insulation and dump most of the coil energy into the coil driver clamp which may not be designed to take sustained abuse like this.

As someone else asked, have you checked the actual timing with your timing light? This is a much more fundamental test that should be done before diving into coil waveforms.

[Edited on 26/7/15 by MikeRJ]