Engine Solved: Need help with mini starter

Dan02gt

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Mar 2, 2003
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So I pulled the K member on my '91 to replace the oil pan and clean up a few things while I had it all apart. I figured while I had it apart I would go ahead and replace my starter with the newer style mini starter. I bought a Bosch SR7542N from Rock Auto for a '93 Mustang. The problem is that it will not engage the flywheel. The starter just free spins. Has anyone had this issue before? Everything I read said this swap is plug and play. My car is a manual and has a factory replacement flywheel that's been on the car about for about 5000 miles. Any ideas? Maybe I got a defective starter?
 
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Kid wita 5oh

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You went from a stock style starter to the mini with a solenoid on the starter, correct?

You have to power the small post on the solenoid....sounds like you didn't.
Make a small jumper(10g should be fine) from the large post,where your stock cable is, to the small post.
 

HoustonGlock

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Connect the large cable from the starter to the positive battery cable side of your existing fenderwell solenoid.
Connect a small gauge wire, about #12, from the former starter terminal of your existing fenderwell solenoid to the new starter small terminal on it's solenoid.

The new starter needs 12V to it at all times at the large terminal and has it's own solenoid to put power to the starter windings to spin the starter motor and the solenoid also engages the bendix drive with the flywheel.

Don't just conenct a wire direct on the starter from the large post to the small post, The starter will stay engaged and not quit because it then acts as a generator when the engine is running, preventing the starter mounted solenoid from disengaging.
 
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Kid wita 5oh

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Connect the large cable from the starter to the positive battery cable side of your existing fenderwell solenoid.
Connect a small gauge wire, about #12, from the former starter terminal of your existing fenderwell solenoid to the new starter small terminal on it's solenoid.

The new starter needs 12V to it at all times at the large terminal and has it's own solenoid to put power to the starter windings to spin the starter motor and the solenoid also engages the bendix drive with the flywheel.

Don't just conenct a wire direct on the starter from the large post to the small post, The starter will stay engaged and not quit because it then acts as a generator when the engine is running, preventing the starter mounted solenoid from disengaging.

Can you explain that for me? I ran one for years and never experienced that issue...
Not trying to argue, genuine question.
If power is cut by the fender solenoid how can it stay engaged
 

Dan02gt

10 Year Member
Mar 2, 2003
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So I bought the new starter cable from LMR for this swap. It's got the 12ga cable in it. I connected the main power for the starter to the same side of the starter solenoid as the battery so it's hot all the time. The 12ga wire that connects to the solenoid on the starter is connected to the other side of the solenoid so it receives power when the key is turned. The starter does spin when you turn the key. It just never grabs the flywheel.
 

General karthief

wonder how much it would cost to ship you a pair
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Can you explain that for me? I ran one for years and never experienced that issue...
Not trying to argue, genuine question.
If power is cut by the fender solenoid how can it stay engaged

Electrical science stuff, something about electrical spike or something that causes feed back (?) that makes the solenoid to stay engaged, doesn't happen all the time but when it does it can be devastating, I have my mini starter jumpered and the drive will 'run on' for a second after cranking but doesn't stay engaged in the fly wheel.
When I put this junk back together I plan on using the solenoid to solenoid method, it is the correct way to wire it.
So I bought the new starter cable from LMR for this swap. It's got the 12ga cable in it. I connected the main power for the starter to the same side of the starter solenoid as the battery so it's hot all the time. The 12ga wire that connects to the solenoid on the starter is connected to the other side of the solenoid so it receives power when the key is turned. The starter does spin when you turn the key. It just never grabs the flywheel.
You likely have a bad starter drive.
get a starter from rockauto or the local parts store, it's a common replacement part, 93-4-5 5.0 starter will work.
You could try replacing the starter drive too.
 
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nickyb

WAIT,you now have a pair?
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So Dan it sounds like it's not going deep enough, to get to the flywheel?
Did you compare the new to old one? I'd put them side by side hit them with jumper cables, see how far the gears go
Maybe parts store geek gave you the wrong one?
 

HoustonGlock

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Can you explain that for me? I ran one for years and never experienced that issue...
Not trying to argue, genuine question.
If power is cut by the fender solenoid how can it stay engaged
As I stated, if the starter is engaged and the engine fires up, then the starter becomes a generator, producing 12V at the large terminals and feeding 12V to the solenoid on the starter, keeping the unit engaged.

When direct wired from the large post on the starter solenoid to the small post.

1 way to overcome this is to use a diode from the small solenoid post on the starter to the large 12V + post, thereby only feeding current in 1 directon, from the battery to the solenoid.

Once the primary, fenderwell solenoid disengages, it doesn't allow current flow backwards thru the diode into the starter solenoid.

I'm not good at pictures, but there are many write ups an pictures about how to do this on the interwebs.
 

Dan02gt

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So Dan it sounds like it's not going deep enough, to get to the flywheel?
Did you compare the new to old one? I'd put them side by side hit them with jumper cables, see how far the gears go
Maybe parts store geek gave you the wrong one?
According to Bosch and Rock Auto I have the correct starter for a '93 Mustang 5.0L. I'm going to pull the starter soon as I can get to it and verify the part number physically on the starter and check it against the old one.
 

Mustang5L5

Put lubricant all over the balls
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Pull the starter and take it to your local auto-parts store. The starter has a mechanism inside that will push the starter gear out to engage the flywheel and then retract it when it's deenergized. Sounds like this mechanism is not operating properly and having a parts store test it will likely confirm this

There's nothing special about the starter really. Any 91-95 starter would be a direct bolt in. Just need to do a slight rewire but looks like you've done this.

Energizing the solenoid is what causes the pinion to stick out, and to spin.

1650906767335.png
 
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General karthief

wonder how much it would cost to ship you a pair
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Ford only made two starters for the 289/302/5.0 engines, the latest being the 91 up.
At least that has been my experience and I 've changed a bunch of Ford starters.
 

Dan02gt

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Update. I pulled the starter, used a jumper cable to give it a ground to the chassis, and had my wife try to start it while I watched. The starter worked just like it should with the gear fully extending. So I reinstalled it and the car started, but now it’s grinding some and loud. So what’s my next step? There doesn’t seem to be much in the way of adjustment.
 

Cheapskate207

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He said it’s a Bosch starter from rock auto.

Kinda sounds like a defective starter at this point.
 
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Mustang5L5

Put lubricant all over the balls
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Voltage drop might account for that. Not enough current to properly energize the solenoid. How are you feeding the solenoid?
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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He said it’s a Bosch starter from rock auto.

Kinda sounds like a defective starter at this point.
OK, too much time between that post and now, and recently had an issue with a person that bought a starter from LMR and all he kept saying was 'but it is brand new from LMR ' I kid you not I threw it into the trash can and replaced it with the one off my car.
I have issues.
 

nickyb

WAIT,you now have a pair?
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OK, too much time between that post and now, and recently had an issue with a person that bought a starter from LMR and all he kept saying was 'but it is brand new from LMR ' I kid you not I threw it into the trash can and replaced it with the one off my car.
I have issues.
you need a tissue for your issues general?
 

Dan02gt

10 Year Member
Mar 2, 2003
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Greenville, NC
Voltage drop might account for that. Not enough current to properly energize the solenoid. How are you feeding the solenoid?
I have a new Motorcraft fender mounted solenoid. All the constant hot stuff is connected to one side of the solenoid, including the main power feed to the starter. The dedicated 12ga wire that goes to the solenoid on the starter is connected to the other side of the fender solenoid.

I have decided to send the Bosch starter back to Rock Auto and get a Motorcraft starter.
 
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