Need Help-M42/E21 Starter Motor

[jollE21]

I've done most, if not, all of my M42 swap on my own with the help of a search button.

Since I no longer have the patience to research (I'm nearly done), was hoping you guys can help.

I still need to relocate the battery, however I wanted to make sure all my wiring was in place, including grounds, so I hooked up the car to a battery. Hooked up the positive, then when I hooked up the negative, my starter motor turned on.

I don't have fuel in the car yet and the key wasn't even in the ignition tumbler.

The starter had a whirring noise and was fairly hot, but it didn't seem to turn over the engine. I checked for metal shavings thinking the starter "gear" grinded away against the flywheel, but everything was fine there.

What did I do wrong and how can I correct this?

Thanks folks!


(This pic has no significance to my question, it's just that I usually post pics )

image-1220717332.jpg

[Tom D]

so you have battery voltage connected to the starter motor, but not the solenoid.

[jollE21]

so you have battery voltage connected to the starter motor, but not the solenoid.

Thanks Tom. Forgive me, but electric issues and wiring is all new to me...did I connect something wrong?

I have a new starter and I connected the (3) wires from the engine harness to the (3) terminals.

There are (2) small terminals and (1) large terminal if I'm not mistaken.

I'll take a better pic, but I can't see any other terminals.

image-2669989149.jpg

(Red wire is from fuse box)

[Tom D]

I connected the (3) wires from the engine harness to the (3) terminals.

there is only two wires not three.

battery to the large terminal
black/yellow to terminal #50
remove the third wire

[jollE21]

That worked. Thanks again Tom.

However, I ended up breaking the stud for terminal 30h while putting back on the fuse box wire.

Trial and error...and a lesson on how not to wrench on an engine with an empty, hungry stomach.

I'll be up all night, can the stud be replaced? (I'll wait for your response before I get daring with my left handed drill bits)

[Tom D]

#30h serves no purpose here, don't sweat it.

actually what it does applies to the E30 and not the E21. it supplies a ground for the unloader relay, our cars are wired differently.

- - - Updated - - -

the wire you removed was black/green, right? what do you have the other end wired to?

[jollE21]

#30h serves no purpose here, don't sweat it. actually what it does applies to the E30 and not the E21. it supplies a ground for the unloader relay, our cars are wired differently. - - - Updated - - - the wire you removed was black/green, right? what do you have the other end wired to?

Good to know. The wire I removed was indeed black/green.

Below is a pic of the 3 wires I mentioned;


image-3540753743.jpg


The below diagram will explain what I did earlier: I connected the larger wire and the fuse box wire to Terminal 30h. Black/green was connect to Terminal 30. Lastly, black/yellow was connected to Terminal 50. This created the whirring sound.


image-3786259285.jpg


Once I removed black/green from Terminal 30. The noise stopped when I connected the battery

I then went to connect the the fusebox wire to Terminal 30h, which ended up braking.

From what it sounds like, black/yellow to Terminal 50 is all that's needed?


My broken stud...
image-460721878.jpg

[Tom D]

black/yellow to #50, this is the solenoid's switching wire from the ignition switch.

positive battery cable to #30, this drives the starter motor when the solenoid is switched on

#30h is left blank, it is the grounding path for the E30's unloader relay.

large gauge red wire, this is the feed for the fuse box's battery buss bar and should be hot at all times. it can be wired to solenoid #30, alternator #30, or directly to the battery (or battery cable)

battery cable needs to be connected to both the alternator's #30 and the starter's #30. you can do this by running the battery to one and then jumping a wire to the other.

- - - Updated - - -

My broken stud...
image-460721878.jpg

just so you know, the stud you broke is terminal #30, not 30h.

if you can get the solenoid off you can replace the bolt from behind.

[jollE21]

Got it. I understand now. The diagram was throwing me off in terms of my explanation. It doesn't appear to be an exact diagram of the M42 starter.

The pic below should help better explain what I had originally connected and what broke;


image-62808014.jpg


#3-Black/yellow to Terminal 50
#4-Black/green to Terminal 30h
#1-Battery Feed + Fusebox Line to Terminal 30

What I broke is the stud for Terminal 30, #1 in the pic above. Before breaking the stud and after removing the black/green wire the whirring sound stopped, so it seemed to have been connected correctly. I effed it up by tightening the bolt on Terminal 30 too tight.

Hoping to have the starter replaced this week and connect the wires correctly.

Now that I understand that portion of the wiring, I'm a bit confused about the alternator wiring....you mentioned it'll need to be powered by the battery...isn't it already powered from the engine wiring harness?

Appreciate the help.

[Tom D]

the battery needs to be connected to four different items;

starter, heavy gauge wire which you have already done

battery buss bar in the fuse box, your medium gauge red wire connected to #30 at the starter

alternator, run a heavy gauge jumper wire from #30 starter to #30 alternator

main relay, medium gauge wire to one of the relays you have mounted on the firewall.

all of the above will be powered constantly and except the main relay, none of them are fused. the main relay takes a 30amp fuse before the relay.

the blue wire in the harness to the alternator is an 'excite' wire, its job is to provide a small charge to the alternator to get the charging system to jump start.

[jollE21]

Tom - Starter solenoid has been replaced, I now have a new terminal and more importantly, time to do this.

Let me reiterate what you said so were both on the same page.

1.) Heavy Gauge wire to Terminal 30/Starter, along with black/yellow wire to Terminal 50/Starter and we're leaving the black/green wire off of Terminal 30h/Starter. All of these wires originate from the original wiring harness on the M42.

2.) Red Medium Gauge Wire from fuse box bus bar to Terminal 30/Starter.

3.) Heavy Gauge Wire from Terminal 30/Starter to Terminal 30/Alternator

4.) Main Relay - For this, I've left the 3 relays intact from the moment I pulled the engine. Below is a pic to indicate the wiring (I've placed the relays in random order when mounted to the wall, but wiring was not removed from either the O2 Sensor relay, DME Relay, or the Fuel Pump Relay). Will I need to connect any further wires from here to the battery? I thought that the wiring was already connected to the battery from through the wiring harness.


image-4292089619.jpg

[Tom D]

I got a guestion first, how did you wire the battery from the trunk to the engine compartment?

- - - Updated - - -

and yes to 1.) 2.) and 3.)

[jollE21]

I got a guestion first, how did you wire the battery from the trunk to the engine compartment? - - - Updated - - - and yes to 1.) 2.) and 3.)

I'm using a similar setup that would have been used on an E30.


image-1071644753.jpg


Hopefully this helps answer question 4?

Appreciate your help with this.

[Tom D]

so you're using wire #3. this wire has a 30 amp inline fuse and is used for firing the main relay, fuel pump relay and the ecu.


here's the wiring schematic, wire the red wire from the engine harness to wire #3 coming from the battery and then make sure each of the reds are hot at the relays, ecu, etc. this is not the heavy battery cable going to the starter.

[jollE21]

Thanks...so I traced the red wires from the relays and they lead to an eye terminal, see below;


image-2132691311.jpg


This eye terminal then connects to the positive battery terminal post, see below;


image-3538454711.jpg


With that said, it appears that the relays are going to get direct power with this route.

However, based on your guidance, should I cut the terminal eye from the relays and connect it to "wire 3" (from the battery relocation diagram I posted earlier) or can I just have those two terminals (red relay wires with eye terminal and wire 3) meet at the junction post?

[jollE21]

We'll I have lights....been 6 years since the headlights on this car turned on, but it won't start, turn over, or charge the fuel pump (no noise).



image-2383294141.jpg



I'm suspecting it's the key tumbler, there are no "stop" points, meaning the key turns all the way without any stops at ACC, On, etc, unless that's how e21s are.

Any suggestions?

[amarino]

You can try to "hotwire" the car by jumping between the wires on the connector that comes off the ignition switch. I've done it before when my ignition switch died.

I know the fat red one is power and I think the fat purple one is accessory or start-run bus. Then the single black wire that runs off separate is the momentary switch that run to the starter. So in theory if you jump between the fat red one and the single black one it should power the stater, at least on my '81.

I guess first make sure that the fat red one is getting power as that powers all of them.

Also this is the rectangular black connector under the dash.
If you want I can go take a look with you and I'll bring my multimeter.

One more thing, is the battery new or the same one it had 6 years ago?

[Tom D]

should I cut the terminal eye from the relays and connect it to "wire 3" (from the battery relocation diagram I posted earlier) or can I just have those two terminals (red relay wires with eye terminal and wire 3) meet at the junction post?

it really doesn't matter, either way the relays and the ecu will receive power. however, wire #3 is protected by an inline 30 amp fuse, whereas the battery post is not.

if you do decide to use #3 then make sure there is continuity, the inline fuse is buried under a heat shrink and if its blown you would not see that it was.

- - - Updated - - -

at the connector under the dash and on the car side not the ignition switch side:

check the red wire for power, this is the battery buss bar.

jump the red wire to the green wire, this is the run/start buss bar and this will power up the car's circuits.

temporarily jump the red wire to the black wire, this is the starter's solenoid engagement circuit.

- - - Updated - - -

We'll I have lights....been 6 years since the headlights on this car turned on, but it won't start, turn over, or charge the fuel pump (no noise).

if you have lights that means that the key is indeed switching between the battery and the run/start buss bar. try jumping the red to black.

[amarino]

if you have lights that means that the key is indeed switching between the battery and the run/start buss bar. try jumping the red to black.

I didn't think about that. It may be that plastic ignition switch broke. Had the same thing happen to me.

You can also try jumping the fuel pump as explained in the DIY/FAQ thread.


And let me know whens a good time to go over. Evenings are best for me.

[jollE21]

It starts!!!!!!!!! THANKS TOM AND ALEJANDRO!!!! Beer is on me.

[amarino]

So what was the problem? Battery?

[jollE21]

So what was the problem? Battery?

The ignition switch. The tumbler is broken and didn't want to engage. I'll show you when you come by. (I should be free this week)

I ended up putting a push start button for the starter signal and used 2 (20A) toggle switches for ACC and the ignition signal. (Used JRCooks hot wire guide)

[amarino]

because racecar!

Very nice. I'll text you in the AM and we'll work something out.