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VL Turbo coil pack install - won't start with voltage drop


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Hey legends.

Have installed some PRP supplied coil packs via an expansion loom on a previously-running VL Turbo with G4+ plugin. Changed the Ignition mode to Direct Spark. Have left the Dwell table alone for the moment given I'm already having voltage issues. Dwell lower than recommended values but I'd still expect the car to start.

Battery (relocated to boot) is in excellent condition with full charge (even tried connecting another running car battery via jumper leads).

Coil packs working great - testing individual coils works perfectly. While cranking I observe (via Runtime values or by watching the Dwell table) the battery voltage dance around quite a lot. Occasionally dropping well below 10v which proves insufficient for the ECU and the green light turns off (and the laptop disconnects). Car backfires every now and then, but never starts. Always seems to drop too much voltage and stop cranking before starting.

I'm anticipating an electrical issue here (as has plagued the car since I bought it - 35+ year old wiring is not my favourite), however, I thought I'd ask here first incase there is potentially some ECU controllable influences that might be at play - and that I can easily test with a few clicks, much easier than anything involving my multi-meter.

Incase it's of value, I have attached the tune.

Really appreciate any help.



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I would guess most likely the trigger offset is wrong.  With a distributor the coil sparks for every TDC, and the rotor then sends the spark to the correct cylinder.  So the trigger offset could be 120,240,360,540 degs out and you wouldnt know, it would still run.  With direct spark the ecu needs to send the spark to the correct coil - so there is only 1 trigger offset that will work. 

Have you checked ignition timing?  If you have and it looks ok then you could just be 360deg out - so add or subtract 360 from your offset.    


If you continue to have dropouts when cranking, check the voltage on pin 34, this comes from the ignition switch and it is quite common to find a very low voltage on that pin when the ignition switch contacts are worn.  The ECCS relay will drop out if pin 34 drops below about 7V.

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@Adamw you are literally the mannnn... thank-you so very much for the speedy and detailed reply. I made the assumption the timing would be 'fine' since the car was running. But, of course, when you say it, it seems obvious that the timing doesn't matter to the ECU with a dizzy. I'll check the timing tomorrow. Thanks again!!!

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