Installed High Torque Mini Starter ... Battery Draining

[Bruners4]

As for the starter staying engaged for a second or two at startup. It is how it is wired. The quick and dirty (and hack easy) is to put a jumper to the solenoid on the starter to the switched battery feed cable. The correct way is to move the battery feed cable to the battery side of the solenoid so it is always hot. Extend the little jumper that the starter probably came with and put that one the fender solenoid where the starter cable once was.

What is happening...
The new starter with the fancy permanent magnet motor is also a pretty decent generator. When the engine starts and you release the key, the original fender starter solenoid disconnects power to the starter. The starter has momentum and has to spin down. As it is spinning down it is generating enough power to keep the starter mounted solenoid energized. Not from the key, not from the battery, but from the starter acting as a generator. So long as the sprag releases, engine power is not put into the starter and it will release as soon as the starter spins down slow enough to not generate enough pull in power on the solenoid.
By doing the rewire described above the fender solenoid shuts off power to the starter solenoid. The power as the starter spins down doesn't go anywhere, and not into keeping the starter mounted solenoid pulled in. This is factory Ford wiring in the 90s when factory mini starters were first used. Ford did this to make the new starters work with the old wiring infrastructure.

And to add to this. If using the explorer circuits without a 30A relay to energize the 'old' starter relay and the starter solenoid, the ECU cannot handle the amount of current needed to pull in both. The current draw will lower the voltage enough to pull in the heavy relay on the fender but not the solenoid on the starter. The ECU start signal has to only energize a 30A relay that then uses battery power to energize and pull in both the heavy relay and the starter solenoid. Chased this for a while until a Fluke DMM with a minimum hold display recorded it in the S terminal for me. I also tried the starter solenoid jumper wire with the same results as described by Broncobowsher

 

[SLOWnEASY]

@Broncobowsher I'm trying to follow. Is this what you are saying he should do?

 

[Broncobowsher]

That looks right. And keeps the I-post on the original starter solenoid active. Which often comes in handy to get an engine to start.

 

[DirtDonk]

And to add to this. If using the explorer circuits without a 30A relay to energize the 'old' starter relay and the starter solenoid, the ECU cannot handle the amount of current needed to pull in both.

Guess I'm not understanding how it works. Curious why the ECU even sees both?
Would not it only see the current needed to energize the main starter relay?
Certainly nothing wrong with letting another 30a relay do the job. Guarantees the computer only sees a very minimal load.
Do the newer Fords that still use the old style starter relay, have an actual "start relay" in the power box, in addition to the usual ECU power relay?

The current draw will lower the voltage enough to pull in the heavy relay on the fender but not the solenoid on the starter.

That's my question essentially. The "S" post should ONLY see the load of the fender mounted relay. Should be completely isolated from the starter solenoid.
Hence my previous questions...

The ECU start signal has to only energize a 30A relay that then uses battery power to energize and pull in both the heavy relay and the starter solenoid.

Yep, I can see the minimal load needed to trigger a 30a relay as being a benefit no matter what. Other than perhaps just the issue of adding yet one more component to fail.

Chased this for a while until a Fluke DMM with a minimum hold display recorded it in the S terminal for me. I also tried the starter solenoid jumper wire with the same results as described by Broncobowsher

Interesting. Got a link to that previous discussion? Glad you got your issue sorted.
I can see the voltage drop of the starter cranking as causing lots of issues in the computer controlled era. But could it have been other mitigating circumstances/conditions?
Gotta love relays though! Cure for many ills!

Paul

 

[Bruners4]

Sorry DirtDonk but I didn't start a thread on this subject. Just worked through it myself.
Explorer uses a 30A relay to power the starter solenoid in the wiring harness. My setup has a heavy starter relay on the fender and the starter solenoid on the starter. The 'S' terminals are tied together with a 14 ga wire now being triggered by the ECU activated 30A relay. I like the heavy starter relay on the fender as it isolates the battery from the starter to avoid having battery power at the starter and preventing insulation breakdown issues in the starter/exhaust area. Also makes it safe to change out a starter without disconnecting the battery.
Also, an interesting fact with solenoids. They actually consist of two coils within them. Initial energization sends power through the pull-in coil and the holding coil as it requires additional magnetic power to move the soft iron core (Armature) into the coils and pull the starter drive out of it's parked position and into the ring gear on the flywheel. After this action has completed, the armature closes the heavy current contacts removing the negative from the pull-in coil and stops the current flow it requires as the holding coil can now hold the armature in position.
This extra pull-in coil current dropped the voltage low enough to cause the pull-in and holding coil not to have enough strength to move the armature enough to close the heavy contacts in the starter solenoid and power the electric motor to spin. Adding the simple 30A relay as shown in the Explorer wiring cured my problem.