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Discussion Starter #1


Over the years, your old Direct Drive OEM Starter has probably been very reliable. These starters utilize a large field coil to create a magnetic field which moves the drive gear into contact with the flywheel. But eventually you probably have found several performance issues that may have caused undo aggravation.

First off, these are bulky starters that weigh approximately 20 pounds in OEM form. Their large size can create clearance problems around headers and are prone to radiant heat soak that can cause intermittent operation. Additionally the Direct Drive Starters demand a large amount of current which can drain your battery after only a few crank attempts. You may also have found that they do not work as well with high compression performance engines due to the lack of torque output from the drive gear.








In the 1990s, Ford started to use the PMGR (Permanent Magnet Gear Reduction) Mini-Starter. This new design uses a starter mounted heavy duty solenoid and a planetary gear train which allows the armature to rotate at greater speed with increased torque. The PMGR has no field coil and instead uses high performance ceramic-ferrite magnets.

These were found to have many advantages, such as 40% more torque through 4.5:1 gear reduction, much smaller in size providing more clearance and weigh only half as much as the old Direct Drive Starter. By eliminating the field coil and providing an efficent gear reduction, the PMGR requires much less current and substantially reduces drain on your battery.








Selecting the correct Ford PMGR part number is important as the automatic and manual starters are not interchangeable. On the automatic PMGR Starter, the drive gear has a longer nose and the drive gear extends 3/8" further in order to mate with the recessed flywheel ring gear. If the shorter throw manual PMGR Starter is installed in an automatic, it will not engage with the flywheel and simply spin.











Wiring your PMGR Starter is fairly simple and slightly different from your old Direct Drive Starter.

***Move the Main Starter Motor Wire from the "M" switched side of the Starter Relay to the "B" Battery Side of the Starter Relay, so the Starter Motor has constant 12v battery power. The other end of the 4 gauge wire connects to the open large post on the Starter Solenoid.

There may be a second large external post on the PMGR Solenoid with a thick wire that connects power directly to the Starter Motor. When starting, the two large Solenoid posts will interconnect internally allowing full power to the Starter Motor.








***If you run out of room on the Starter Relay "B" Post, install a Power Distribution Stud for all of your accessory wires.

Easy and inexpensive, you probably should have one of these anyway. Simply install the Stud, run your Battery+ to the post and then jumper to the Battery side of the Starter Relay. The Starter Relay "B" post should only have the Battery, Starter Motor and Alternator cables attached.









***Then run a separate smaller 12 gauge wire from the "M" switched side of the Starter Relay to the small "S" Start Post on the PMGR Mounted Solenoid.

You may have to enlarge the 12 gauge wire terminal to make it fit over the larger "M" post unless you fabricate the wire with the correct terminals. Your Ignition Key will then activate the Starter Relay which in turn will send 12v to the Starter Solenoid. When you release the Ignition Key the Starter Relay will open immediately halting power to the Starter Solenoid and will disengage the Starter Motor from the Flywheel. When properly wired, there will be no electrical connection between the Solenoid Start post and the always hot Solenoid Motor post.








Your new PMGR Starter may come with a Bus Bar to facilitate using the original Direct Drive Starter wiring by connecting the relay switched Starter Motor power to the new Starter Mounted Solenoid. DO NOT USE THE BUS BAR or jumper the large Starter Solenoid Main Post to the small Solenoid Start Post in an attempt to eliminate the need for a separate 12v Start Wire.

Doing so can damage your PMGR Starter by causing Starter Run-On for approximately 2 seconds after you release the start key. This is due to the remaining spinning starter motor energy generating mechanical voltage until it has completely stopped.

A motor uses electrical energy to produce mechanical energy, and a generator uses mechanical energy to produce electrical energy. They are very similar. If a motor is spun it will produce electricity.

When the Starter Relay opens, there is no BATTERY power going to the starter, but the voltage generated by the spinning starter motor can keep the new PMGR Starter Mounted Solenoid from de-energizing quickly and retract the gear from the flywheel.

Ford specifically warns:
"! ! ! WARNING: DO NOT INSTALL A JUMPER WIRE BETWEEN THE BATTERY TERMINAL AND THE SOLENOID BLADE TERMINAL AT THE STARTER TO AVOID THE USE OF THE # 12 WIRE. IF DONE, VOLTAGE IS GENERATED TO THE SOLENOID BY THE STARTER SPINNING AFTER THE RELEASE OF THE START KEY OR BUTTON, CAUSING THE STARTER TO REMAIN ENGAGED, RESULTING IN SEVERE DAMAGE AND EVENTUAL FAILURE OF THE STARTER ! ! !"

Remove the Bus Bar or jumper and rewire correctly by using a 12v Solenoid Start Wire... :twak


 

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Good info! :thumbup Many people aren't aware of the danger of allowing the starter to self-energize thru the jumper bar often provided with these starters.



There are a couple of minor corrections, though... :toothless (Big surprise, huh?)
...rare earth magnets.
They're just common ceramic-ferrite magnets; not rare-earth metals. Crack one open & you'll see they're just like BIG window motor magnets.
When you release the Ignition Key the Starter Relay will open immediately shunting power to the Starter Solenoid and will disengage the Starter Motor from the Flywheel.
It doesn't shunt anything when it's off. An electrical "shunt" is almost a short-circuit; when the relay is off, it's an open circuit (the opposite of a short circuit) from M1 to M2.
When properly wired, there will be no electrical connection between the Starter Solenoid and the always hot Starter Motor.
The motor is not always hot - that's the upper solenoid terminal. And the solenoid's windings are always connected to the motor windings 2 ways. When the solenoid engages, it shunts across one of those windings (the pull-in) to reduce its own power consumption. This diagram (created for '66-77 Broncos, but still applicable) shows the internal (and external) wiring for the 2 types:



On the L, the 4 field windings of the older style are shown near the top of the starter motor; the 5th is the rotor (armature) winding. The dotted line through it is the swinging pole shoe.
On the R, the 2 solenoid coils are shown (the hold-in as a solid line, and the pull-in as dashed). There's more detail in these:

.

But your instructions for the wiring are spot-on! :thumbup It's effectively the same as '92-up starter wiring:

 

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Discussion Starter #3
For further clarification,

The main power to the Solenoid is normally open between the two large studs on the Solenoid. When 12v Ignition Power is applied to the small Start Solenoid stud, power goes to the Pull-In and Hold-In Coils in parallel. The Pull-In Coil allows power to feed through the Main Motor Armature Coil and provides a voltage drop limiting the speed of the motor to allow the Pinion Gear to smoothly and safely mesh with the Ring Gear. The Pinion Gear is pushed forward into contact with the Ring Gear by way of a Solenoid Magnetic Switch Plunger that pulls on a Shift Lever which is mechanically connected to the Pinion Shaft.

Then at full articulation, the main Main Contact Plate (Switch) closes internally between the two large Solenoid studs allowing full power to the motor causing greater torque for starting. At this point current is no longer flowing through the Pull-In Coil and the plunger is held in place by the Hold-In Coil’s magnetic force. When the ignition key is released from Start to On, there is no longer voltage at the small Solenoid Start post and main power now briefly feeds through both the Pull-On coil and Hold-On coil in series causing the magnetic fields in the two to cancel each other allowing the Pinion to disengage by way of Solenoid Plunger and Pinion Return Springs. It is at this point the Main Contact Plate (switch) opens and power ceases to the motor.

Looking at the location of the PMGR permanent magnets, I would think that the old school repair method of striking the starter body with a hammer is probably not a good idea.






 

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The Pull-In Coil allows power to feed through the Main Motor Armature Coil and provides a voltage drop limiting the speed of the motor to allow the Pinion Gear to smoothly and safely mesh with the Ring Gear.
The motor doesn't spin.

The solenoid has around 1 Ohm of resistance; the starter windings have about 1/40 Ohm. So when they're in series with ~12.3V (just to make the math easier) across them, 12V drops across the solenoid (making it work) and 0.3V drops across the motor (making it behave like a ground, but NOT nearly enough to make it spin). So during pull-in, the starter doesn't even attempt to spin. That doesn't happen until the copper washer in the back of the solenoid bridges the M1 & M2 terminals (the relay section of the solenoid) killing the pull-in coil's voltage and sending all 12.3V (or whatever) to the motor windings. But before that happens, the action of the Bendix (overrunning drive gear) sliding on the motor shaft's spiral flutes causes the Bendix to rotate slightly, and its spring allows it to hit the ring gear teeth and continue rotating until it aligns. But the motor doesn't turn at all during that process.
...main power now briefly feeds through both the Pull-On coil and Hold-On coil in series causing the magnetic fields in the two to cancel each other...
No current flows thru the pull-in coil while the solenoid's contacts are bridged, and there is no field coming from pull-in; only hold-in.

The starter releases by the force of the spiral flutes on its shaft inside the Bendix NOT being counteracted by the hold-in coil (which is off after the key is released). So the starter's own torque (because it's still working) causes the Bendix to slide forward and disengage the ring gear, which pushes the fork & pulls the plunger breaking the solenoid's contacts & shutting down the motor.

BTW
That's the same way the older starter releases, too. The only real differences in the way they work is that the older one has no gear reduction, the older one uses field coils, and its solenoid plunger is the steel core (pole shoe) from one of those coils.
...the old school repair method of striking the starter body with a hammer is probably not a good idea.
The starter housing isn't flexible enough for a typical hammer strike to shatter the magnets, and even if it did, that's preferrable to letting the starter run-on, or to being stuck out in the woods. So if you've diagnosed your problem and you're SURE it's not external, whacking the starter is still OK. :toothless But I'd always use the hammer HANDLE rather than its face.
 

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You could also bypass the S on the old starter solenoid/ relay and run it directly to the starter therebye elimenating a part to fail.
 

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No, that would cause the ig.sw. to fail. It's not designed to handle the current needed for a solenoid across its S contacts. That's why Ford kept the starter relay in the system. These old ig.sw.s are already known to catch fire - they don't need any more stress.

 

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Only your parts supplier can tell you about relative pricing. I'm reusing the same old-style starter I've been using since I had a carb engine over 15 years ago. I've even driven on it several times, and it just won't die. Nor has it ever killed the battery, even when I drove more than a block on it (towing a loaded trailer).

.
 

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Last year I had the Ford dealer in MErced pull the PMGR starter from my truck and they ended up installing a 1:1....$500 and a few weeks later, the sticky starter condition was back.

Their response, "It is out of warranty period for the repair".

My response..., "Had you suckers properly diagnosed the problem, we wouldn't be here talking about this!!!"

After checking things out, I found that the battery to chassis to starter cable ground cable was on its last leg and was thus drawing lots of current. This only heated the contact of the selenoid up to the point it tack welded itself onto the hot lead and the starter wouldn't quite regardless of key position.

The dealer tried blaming it on the aftermarket PMGR starter...I told them that Henry Curtis Ford in Santa Rosa had put that starter on and that it was years before the symptoms popped back up!!!

Long story short, I went to NAPA and they built me a ground cable. Ford says they're obsolete.

Installed cable and the truck even starts sooner now.

Symptom gone.
 

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An '88 (from your profile) wouldn't have had a stock PMGR. Why did a dealership put an aftermarket one on? And the only thing special about its ground cable is the tab soldered into the middle for the frame, which isn't necessary for starting, and is easy to work around with a 2nd short cable.
 

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That may be Steve but I have seen this mod on mustangs and if the firewall relay is left in the circuit the starter will over-run because it does not release fast enough. The new vehicles do not have the big relay[solenoid some call it] although some have a different switch or just a small relay in the junction box.
 

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...I have seen this mod on mustangs...
How many have you PERSONALLY inspected & diagnosed?
...the starter will over-run because it does not release fast enough.
Exactly what do you mean by "overrunning", and how fast does the relay need to release to prevent it? Why does it only affect modded PMGRs, and not factory PMGRs or older starters with that same relay?
 

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Steve yes personally, by over-run I mean they do not stop and disengage quick enough.
I am not sure why but I have seen it more than once. BTW I am a ford senior master tech and have been for a long time, not just some inexperienced forum guy putting on a show.
 

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Great - then you can answer the technical questions I left out before! :thumbup

How did you determine that it was the relay causing them to keep running? How did you determine that the relay wasn't releasing fast enough, if you don't know what "fast enough" is? If you don't know why it's only the modded PMGRs that suffer from the relay, WHY would you think it's the relay causing it? Maybe it's any of a thousand other things that those owners did when they swapped in those starters. Did you check all of them to make sure the solenoid circuit wasn't bridged to the starter power circuit anywhere in the cars? Because that's the ONLY way a solenoid starter can stay engaged with a relay; by self-energizing.

And what are the effects & dangers of the starter continuing to run for however EXTRA-long (you didn't say how long) these were running on? Since the Bendix is specifically built to prevent overrunning from damaging the starter, what's the big deal? Do they stay in for 1/10sec too long, or 10 sec too long?

But you still didn't address the issue that you raised about running that much current thru an old ig.sw. - as a long-time Sr.Mr., you must be familiar with that FSA.
I am thinking maybe one or two???:histerica:histerica:histerica
You might think that, but he still didn't claim even one. :shrug So AFAWK, he's only seen them in parking lots. All we know is that he's...
...not sure why...
 

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Steve, thank you for asking the relevant questions (and sharing diagrams with me personally). I am staring down the barrel of upgrading to one of these and it helps to get a little more info from the technical side.
 

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Tagging to upgrade my starter in the very, very near future. Thanks to SeattleFSB, banned Steve83 andFSB!! Oh, could any or all of you guys cough up a little money, just a little as this really isn't that expensive and I think my "zone" lifetime warranty starter is on its way out. Besides, every little bit helps.

tim
 

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Tagging to upgrade my starter in the very, very near future. Thanks to SeattleFSB, banned Steve83 andFSB!! Oh, could any or all of you guys cough up a little money, just a little as this really isn't that expensive and I think my "zone" lifetime warranty starter is on its way out. Besides, every little bit helps.

tim
Did you ever do the upgrade?
 
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