My spark during cranking is very weak. It gets very strong as soon as the key is released. The car won't start while cranking, but fires right up as soon as you let go of the key.
Whats up with this?

 

make sure your battery is in good condition & fully charged. check the starter for proper current draw. if your good so far, check the voltage at the coil while cranking, if its low, run a jumper wire from the battery to the ignition switch side of the coil & recheck it. if its good with the jumper, check the bulkhead connector, ignition switch & its connector for a bad connection & signs of over heating. check the fuse link that powers that part of the ignition switch & its connections.
also check all your grounds, battery to motor, battery to body, & body to motor.

 

OK. Everything you said makes sense. This is a motor swap which I just finished, so any of the connections is suspect.
The battery is brand new. However, the starter could be drawing too much power. It cranks the engine pretty slowly compared to my v6, even fully charged. I'll see what the battery voltage drops too when I crank it over. Thanks!

 

I just checked, the battery voltage drops down to about 10 while cranking. The coil sees 9.5-10 while cranking. Maybe My starter is dawing too much power?

 

sort of same problem how do you jump the coil?

 

The big pink wire on the external coil is +12 v. Just jumper that to the battery.

 

okay i'll try it.