Engine 2004 V6 to V8 swap starter problem.

Just wondering. Did you check the negative ground between the motor and the battery?

Did you re-attach the grounding strap between the left hand motor mount and the frame rail? This grounding strap is frequently over looked during a motor swap.

Note, I think you have two problems. A problem in the neutral safety switches (NSS) and with the starter itself. IMO you should focus first on the starter. The starter should work normally IF the starter solenoid is jumped.

Here's some information on how to test the quality of the ability of the circuit to carry high current. Don't focus on the specific parts being tested but try to understand the CONCEPT behind the test.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

SnowB said:

I'm not sure about what you mean with the concept

Click to expand...

Did you actually review and watch all of the information provided in the "howto perform a charging system voltage drop test"?

The example provided gave an example of how to do a voltage drop test on the alternator. However a voltage drop test can be done on any circuit the MEASURE the quality of that circuit to carry high amps (such as a starter circuit). This is the CONCEPT behind a voltage drop test.

As for additional grounds, there is another that is attached to the lower front left of the motor. It's a very heavy black wire.

If you are unable to understand the concept behind a voltage drop test another way is to measure the voltage at the starter and starter case. Note this reading. Now engage the starter. What does this voltage change/drop to? If there's a poor electrical connection the voltage will drop very low. This method will not pin point where the problem is only that you have a problem.

Note, if the voltage does not drop at all, then likely the starter is not actually engaging and drawing any real current.