Coil pack or Edis???

[petrolhead]

Engine is turning over strongly, fuel is def getting through. No spark at plugs, engine makes no hint of firing up.

Is this diagnosis correct? With the ignition on all 3 wires on the coil pack read 12V. I assume that the coils are triggered when their repective wires drop to 0V and they feed off the central live wire which is 12V constant.

When turning the engine over I get a voltage drop in those 2 wires as expected and the central wire remains constant. However, I get no spark at the spark plug but I do get a very weak flickering voltage at the ends of the leads when measured with the multimeter.

Is there a test I can do for the Coil pack and EDIS module.
Thanks in advance.......

[Oliver Sedlacek]

Sounds like the coil pack to me. The EDIS will charge the coils up by pulling the end connections down, and you get the sparks when the current to the coils is cut.

[MartinM]

Coil packs are very simple and reliable very beasts. You could check it on the bench/separate from the EDIS by checking its primary and secondary resistances and attempting to make it produce a spark by having the centre pin at 12v and dabbing one of the side pins to earth (with an HT lead and an earthed spark plug connected) - similar to the last two tests I quickly found via Google at http://www.clarks-garage.com/shop-manual/ign-04.htm

...then, more details are needed....

Is this a new install, or has an existing install stopped working?
Is the MJLJ in the system or not?
Are you really, really sure you've got no EDIS wiring errors?

If it's a new install, and even if the MJLJ is on the bench rather than in the car AND you've completely messed up the trigger wheel/sensor/TDC alignment you should get sparks at some point when cranking.

If you've got the VR sensor, EDIS module and coil packs wired properly, you should be able to start the car without the MJLJ being present and get a rock solid 10BTDC spark - in fact that's the way I approach installations. Only then do I introduce the MJLJ...

Tell us more and I'm sure we can help....

[petrolhead]

This is a new megajolt install. I've double checked the wirng, my first thought was the VR sensor, but this is 0.75mm from pulley. Primary and secondary resistances check out OK. I've double/triple checked the wiring, the only point of contention is the 'Coil A' and 'Coil B' wires, I can't identify which way they go round so any other changes I make I try both combnations. Megajolt gives 5V in all the right places. I've tried unplugging the megajolt so it will just run in limp home but it still makes no hint of firing up. I appreciate the coilpack test advice. I've bought new leads and will try new plugs and coil pack tonight, I'll let you know how it goes. Any other ideas??? the fact that it is showing absolutely no hint of firing up makes me think it is something very simple. thanks in advance.....

[MartinM]

Well it probably is simple - it IS a wiring problem (one common gotcha is to have one of the VR sensor leads accidentally earthed - neither should be) OR it IS a VR or EDIS or coil pack problem!

Strongly recommend you get leave the MJLJ on the bench and get 'limp home' mode working first.

I've never tried these, but with only a multimeter:
- you should be able to detect a non-zero a.c. voltage across the VR sensor wires when cranking. It might be pretty small, but should be greater than the zero you see when not cranking (again VR sensors are very simple and very robust, so they're unlikely to fail in themselves - the wiring to them may be a different matter, however)
- you should be able to detect a non-zero d.c. voltage on the PIP line out of the EDIS when cranking - it's actually a series of 0-12-0v pulses but they should register on a multimeter. Without the MJLJ connected, they serve no useful purpose except to confirm that the EDIS module is probably detecting the VR sensor signals properly
- you should be able to detect a non-zero (but not a constant battery voltage level) d.c. voltage on the EDIS coil output lines when cranking

The tool you really need in these difficult circumstances is an oscilloscope - any chance of getting hold of one?

[petrolhead]

I replaced the leads, no joy previously I had pulled out No.4 spark plug and checked for spark, there was none. After replacing the leads I pulled out No.1 plug and it was giving an intermittent spark, every few seconds. I had an idea that although the plugs had had little use, the monthly start/ getting fouled /and defouling might have knackered them. Hey presto, replacing the plugs and she fired up. Running better than ever.

To summarise, it was something simple. Thanks very much for yr time and advice Martin.

[MartinM]

Excellent news! Well done!

[Oliver Sedlacek]

Always replace the cheapest bits first!