M5OD swap starter wiring issue

CountryBoy704 · Jul 29, 2013

Putting a '97 4.0 M5OD into an '87 auto 2.9 ranger. I have the tranny installed and bypassed the NSS by cutting off the 5 pin plug and crossing all the wires...yes my reverse lights are on by thats an easy remedy later.
So I'm having trouble with the starter wiring as the '97 starter introduced a second solenoid into the mix, I am getting power at the starter and can hear the older solenoid (on the firewall by the battery) engage when the key turns. I tried wiring it up as shown at the bottom of the 2.9 to 4.0 clutch swap tech article to no avail, any suggestions?

adsm08 · Jul 29, 2013

This always seems to end up being harder than it really is. I'm not convinced that the swap article explains it that clearly.

You need two wires for your 4.0 starter. Take your original starter wire, in it's original location, and hook it to the little post on the 4.0 starter.

Then take a 6" section of battery cable with two big eyes on it and run it between the big post on the starter and the side of the original starter relay that all of your other wires go to.

CountryBoy704 · Jul 29, 2013

ok so I placed a jumper between the two bigger posts on the original starter solenoid. But both posts on my starter are the same size would I run the lead to the solenoid post on the starter or to the other post which I think would bypass the solenoid?

There's also a smaller wire which runs up into the harness on the drivers side, It's currently hooked back up the way it was do I need to do anything with that one?

adsm08 · Jul 29, 2013

There should be 3 posts on the starter. Two larger ones, one already has a braided wire on it and should be ignored.

The other large one needs constant battery feed.

Then there should be a smaller one that gets hot in start.

The red and blue wire at the original relay needs to be on the small post like it was before.

Postin' from teh Galaxy

CountryBoy704 · Jul 29, 2013

The constant feed comes from jumping across the old solenoid correct?
I feel like I've got it wired up right, starting to suspect that smaller wire or another problem I'm gonna go poke around with the multimeter a bit.

RonD · Jul 29, 2013

Just FYI, you can leave all the wiring stock, and just put a small jumper on the new starter solenoid, large post to small post, much easier.

The starter solenoid on the fender is just a big relay.
One large cable from the battery, one large cable to the starter motor.
Then one smaller wire from the Key switch, this post is labelled "S".

Key switch---------\
Battery-----------solenoid--------------Starter motor

When key switch sends power on that small wire the "relay" closes and full battery amps/power is sent to starter.

The new starter with solenoid attached works the same way.
So to Close that "relay" you just need to supply the small connector 12v, which can be done by the large connector since it has 12v when old solenoid is closed.
So a 4" wire is all you need, easier to work with, a 1" would fit, lol.

The old solenoids wires:
The old solenoid will have an alternator wire connected on the same post as the battery cable.
And depending on the ignition system there may be a smaller wire on the Starter motor wires post, that wire sends 12v to the Coil only when engine is cranking, it gives the coil a hotter spark for starting, on the really old 4 post solenoids this wire was connected to the "I" post.
It was moved to the starter motor wires post when 3 post solenoids were used, does the same thing.

So
Key switch---------\
Battery-----------solenoid-------------starter motor
Alternator-------/............\------------Coil

And there may be another wire on the battery's solenoid post to the power distribution box.

4x4junkie · Jul 30, 2013

^^

No that'll cause a starter run-on issue for a couple seconds after you release the key (I know, I tried that at first lol).

Here's a diagram of how I ended up wiring mine:

Hope that helps

.

adsm08 · Jul 30, 2013

RonD said:
Just FYI, you can leave all the wiring stock, and just put a small jumper on the new starter solenoid, large post to small post, much easier.

Yeah, that's a no-no chief.

It causes a bit of feedback through the circuit as the starter spins and causes the run-on that 4x4Junkie mentioned.

It's also kinda not good for the starter.

4x4junkie · Jul 30, 2013

Yeah it made a pretty nasty grinding sound lol

adsm08 · Jul 30, 2013

It did start the truck though.

I didn't hook up the jumper, I just got confused while I was wiring it and put both starter wires on one post of the relay.

4x4junkie · Jul 30, 2013

Yes, it did start. It's after the engine starts and you let go of the key it goes *Ch-ch-pbpbpchshZZZZzzzzzeeeoo* :icon_twisted:

adsm08 · Jul 30, 2013

Yeah, that was fun.

The first time I fired it up was after a marathon week of working 20 hours days fighting rusted nuts, running for parts, and trying to feel my fingers, only taking one break for Thanksgiving Dinner and heard that I thought, "WTF? Eh, forget it, it runs".

RonD · Jul 30, 2013

4x4junkie said:
^^

No that'll cause a starter run-on issue for a couple seconds after you release the key (I know, I tried that at first lol).

Here's a diagram of how I ended up wiring mine:

Hope that helps

.

Not sure why it doesn't work, I will take your word for it, and the others

Nice diagrams

When fender solenoid cuts voltage(key at RUN position) there should be no reactivation because there is no voltage, and Bendix drive is retracted.
There is no electrical loop, but there could be a backwards loop.
Only thing I can think of is that the starter motor turns into a generator briefly, as battery 12v drops starter solenoid is still passing voltage(closed) so "generator" pushes up voltage which reactivates opening solenoid which tries to reengage gear, so you get the grinding.

I'll have to test that one day, maybe add a resistor to that jumper, lol.

4x4junkie · Jul 31, 2013

RonD said:
There is no electrical loop, but there could be a backwards loop.
Only thing I can think of is that the starter motor turns into a generator briefly, as battery 12v drops starter solenoid is still passing voltage(closed) so "generator" pushes up voltage which reactivates opening solenoid which tries to reengage gear, so you get the grinding.

I'll have to test that one day, maybe add a resistor to that jumper, lol.

Yep, that's exactly what happens. The motor still spinning keeps the motor's solenoid engaged until the motor finally spins down enough that the solenoid (and the pinion gear) finally drops out. During that time the gear grinds against your flywheel.

adsm08 · Jul 31, 2013

RonD said:
Not sure why it doesn't work, I will take your word for it, and the others

Nice diagrams

When fender solenoid cuts voltage(key at RUN position) there should be no reactivation because there is no voltage, and Bendix drive is retracted.
There is no electrical loop, but there could be a backwards loop.
Only thing I can think of is that the starter motor turns into a generator briefly, as battery 12v drops starter solenoid is still passing voltage(closed) so "generator" pushes up voltage which reactivates opening solenoid which tries to reengage gear, so you get the grinding.

I'll have to test that one day, maybe add a resistor to that jumper, lol.

A diode would be a better choice. A resistor might keep it from working at all.

Postin' from teh Galaxy

M5OD swap starter wiring issue

Member

Senior Master Grease Monkey

Member

Senior Master Grease Monkey

Member

Official TRS AI

Forum Staff Member

Senior Master Grease Monkey

Forum Staff Member

Senior Master Grease Monkey

Forum Staff Member

Senior Master Grease Monkey

Official TRS AI

Forum Staff Member

Senior Master Grease Monkey

Sponsored Ad

Sponsored Ad

Member & Vendor Upgrades

Truck of The Month

Recently Featured

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store

Sponsored Ad

Sponsored Ad

Sponsored Ad

Amazon Deals