Modified electrical/starting problem..., ... Found the problem. Need a solution. Options

[BMXerror]

Calling all racers. I haven't had much time to mess with the 914 since finishing the SDS install nearly a year and a half ago. It's got a pretty decent baseline map in it (street tune, no dyno), but it's always been a hard cold starter. It will crank and crank and nothing, but as soon as you let go of the starter it stumbles and tries to fire. Keep doing this and it will eventually start. Just this past few weeks I've gotten back into it and am trying to resolve this issue. And after successfully testing one of my father's theories, I've found the problem. The starter is robbing too much power from the coils, and they're not firing while the starter is engaged. I confirmed this with an inductive timing light. So the question is what to do about it.

Some background info:
*The starter is an ebay high torque starter and has been installed for some time. It started just fine with the D-Jet system.
*The injection is an SDS EM-4F, meaning it's crank fired with two coil packs(batch fire). Supposedly it's a pretty hot spark.
*Part of my SDS install was relocating the Battery to the front. Currently I have the secondary lead on the starter running through the tunnel, and the hot lead that runs the injectors and coils pulled off of the starter pole. However, in my testing I ran a test lead direct from the battery to the coils, and it didn't seem to help the situation.
*I'm seeing a voltage drop at the battery to 8.5V when I hit the starter.
*The battery is fairly new and seems strong, reading 13V at rest.

Any recommendations on how to resolve this problem. It just seems to me like those coils and that starter are too much for that system. Input appreciated.
Mark D.

[BMXerror]

Well, that was easy... Tighten the f-in ground, dumbass! (IMG:style_emoticons/default/slap.gif) The connectors on the ground switch were loose. Not sure when or how that happened, but they were. I tightened them up and it starts much easier, though I haven't tried to cold start it yet. I also checked the voltage at the battery and it drops to 10.5 when cranking now. I'm not sure if this is still unacceptable or not, but it's an improvement.
That explains why the situation has seemed to deteriorate. I remember the first night I started it up on the new injection system, reaching in the window, hitting the starter switch, and it firing up without all that hassle. I must've been working on it shortly thereafter and pulled the ground off or something, because it's been doing this for months. Just haven't had time to investigate.
Thanks KG6DXN. You had me looking in the right spot. What do you think of the new 10.5 cranking voltage?
Mark D.

[Mike Bellis]

What do you think of the new 10.5 cranking voltage?
Mark D.

I would say that is a normal voltage drop. You could improve it with a bigger battery cable. #4 is a little less than optimal for the distance. See if you can find some 1/0 to 4/0 welding cable. It is fine strand flexible cable. I would also bond the ground up front to the chassis before it travels to the rear. After 40 years, our chassis ground is not what it used to be.

#4 is good for 70 amps (AC current). DC current takes a larger wire. Starters can draw up to 200 amps DC peak... Peak current happens at maximum torque (start up) on an electric motor.

This is why Edison needed a 3" diameter conductor to push 1/4 mile (DC current). Tesla pushed the same 1/4 mile with a #8 conductor (AC current)... The rest is electrical history... BTW most of Tesla's inventions are still in use today. Not the same for Edison...