Starter Wiring Help

[Uwon]

Finalizing all the wiring hook-ups and getting very close to start-up day on my RST build (Evolution of a Carrera RST). I now have an issue in that I can't figure out exactly how the donor '86 was wired. So I need some help from the brain trust.
Issues:
1. Looking at the starter wiring diagram for the '86, I cannot decipher which terminal is which on the starter. Is terminal #50 inboard (closer to the trani)?



2. The donor car had a relay to actuate the starter. Terminal #87 on the relay was connected to terminal #15A on the starter. Relay Terminal #30 was connected to the starter but I don't know which 30 or 50?
Any ideas would be really appreciated.
Thanks in advance.
Cheers,
Johan

[timmy2]

Post up a schematic of the relay so we can see what terminals are NO and NC as well as the coil designations. Maybe even a photo of the relay and starter.

Normally you want the yellow wire in the engine harness to energize the coil with the other side of the coil run to ground , and then run 12v to the NO relay contacts from the main power terminal 30 and then the other side of the NO contacts run back to terminal 50 on the starter.

[Uwon]

Dennis,
OK, let's start over again. The donor crashed car was damaged in the area of the starter so I had to do some cut-out to retrieve all the electrical harness, etc. It was difficult to keep track of all the connections
Here is the wiring schematic from the donor as I can best figure out from the different connections used. Please note that the addition of the relay (usual four/five prong relay) was made to (successfully) solve a starting issue so I would like to retain it.



Sorry, but I'm rather ignorant of electrical terminology so I do not understand what you mean by the "coil" unless you are referring to the connection terminal on top of the starter ( I frankly thought that it was a solenoid). Same goes for not understanding NO and NC contacts on the relay.
Hope that you can help, anybody else for that matter.
Cheers,
Johan

[mreid]

15a (87 from the old relay) is the yellow (start) wire connection.

[timmy2]

Here is a diagram of the internal workings of a Bosch relay.



The coil (solenoid) that makes the relay operate internally by inducing a magnetic field around an iron bar is powered by applying 12 volts to terminal 85 or 86 of the relay and connecting the other one to ground. Then the relay acts like a switch closing the NO (normally open) contacts between terminals 87 and 30 so that whatever is connected to those terminals are now a complete circuit. Like turning on a light switch.
(NC denotes normally closed contacts 87a to 30, not used in this application)

You need to:
Connect the yellow wire to terminal 85 or 86 and then connect the other one of the 2 you didn't use to ground at the transmission ground strap location.

Then connect a wire from the starter main battery connection terminal 30 to terminal 87 of the relay. Then run a wire from terminal 30 of the relay to terminal 50 of the starter.

When you turn ignition to start the relay coil is energized closing the circuit to energize the starter solenoid.

Google Bosch relay to learn about how it works if my explanation is still too technical.

Sent from my iPhone using Tapatalk

[timmy2]

Looking at your color drawing again...
What is the black wire from ignition key all about? That wire should go to ground.
Green wire should go to terminal 50.
Starter is grounded by the case, not a terminal.
15 should be empty.

[ossiblue]

This is getting a bit confusing so let me see if I can clear things up a bit.

First of all, the diagram is of an aftermarket hard start relay in which the yellow wire is often directed to be wired to ground. It is a 4-pin relay, unlike the Bosch relay diagram posted by Timmy2. Still, the diagram is wired incorrectly.

Terminal 85 or 86 can be wired to ground, but typically, it's terminal 85. If your start relay is already wired to the yellow wire (yellow from engine harness to yellow on relay harness), that is the power from the ignition switch, so you will need to ground terminal 86 (black wire on the relay harness). As you have diagrammed, your relay will not "click" as it's getting power to both terminals of the relay coil, 86 and 85.

If the relay now clicks by grounding 86 (when you turn the key to "start"), you're ready to move on. Terminal 30 on the relay is correctly connected to power from the battery via the lug on the starter.

Terminal 87 on the relay should be connected to terminal 50 of the starter solenoid.

As Timmy2 posted, the starter is grounded through the transmission and needs no direct ground connection.

[mreid]

I think you guys are missing the point. It is working wired as above in the donor. The black wire from ignition is ground. He's actually getting switched ground (black) and the start signal (yellow) from the ignition key. The relay is working as designed, it's just not wired in a more conventional way.

[ossiblue]

Originally Posted by mreid

I think you guys are missing the point. It is working wired as above in the donor. The black wire from ignition is ground. He's actually getting switched ground (black) and the start signal (yellow) from the ignition key. The relay is working as designed, it's just not wired in a more conventional way.

You may be right in that the relay is working.

Still, the 87 terminal needs to be connected to the 50 on the starter and not the 15a.

Going back to the OP, the wire from 30 on the relay connects to the 30 terminal of the starter--that's direct power from the battery. When the relay "clicks" that direct battery power will be switched to 87 which should be wired to 50 on the starter.

[mreid]

^true

Not sure how it is working connected to 15a. What is powering the starter solenoid?

[Uwon]

Thank you all for weighing in on my issue. I had some time today to get under tha car and uncovered the following;
Starter is a Bosch model 0001312100 which I think is not a Porsche standard issue.
What I thought was terminal 50 on the starter is actually a thick ground lead to the starter body.
The yellow wire from the charging system going to relay 85 is dead when ignition is off and GROUND when ignition is ON.
Black wire going to relay 86 comes directly from the ignition.
I think that mreid is correct in his initial assessment that the green wire actuated the starter solenoid when the relay is actuated.
Thoughts before I try it?
Johan

[timmy2]

My thoughts are to correct the wiring back to original so it functions the way it is supposed to.
But, that is a lot of work because there has been some unique modification done to make the yellow wire that is supposed to go hot in start go to ground....
In your second post you mentioned doing some cut out and losing track of wiring.

If you want to test it to see if it is going to work, just disconnect the green wire and monitor it to see if it gets 12 volts when you turn the key to start.
If it works and you are happy with it, go for it I guess....

[mreid]

As long as what you have listed as 15a is actually 50, you should be good to go. However, I like Dennis' idea of disconnecting the green wire and testing first. Btw, 15a was used in older vehicles with ballast resisters in the ignition circuit. It bypassed the ballast to provide a very hot spark during starting. Don't use it! Good luck.

[Uwon]

Thanks guys for all your input and help. I will move forward with the final testing as you have outlined this morning.
Here is the amended wiring diagram FYI



And to complete the picture, here is a pic of the starter connections. Note the thick bare with leading from the bottom connection directly to the steel body of the starter.



In retrospect, I should have done a bit more analysis myself before posting. Thank you all for your patience.

It will be a week or so before I get oil in the motor and charge the oil lines. Ill report back thereafter.
Cheers,
Johan

[ossiblue]

The connection from the bottom bolt to the starter is the power feed to the starter from the large bolt above it where the battery cable is connected. It is not a ground connection. When the solenoid is energized by the connection to terminal 50, the two bolts you see are connected together inside the solenoid--that's what makes the motor run. If you shorted the two bolt terminals with, say a large screwdriver, the motor would spin without engaging the flywheel. If you shorted the top bolt terminal with the spade connector on terminal 50, the solenoid would engage the flywheel, the motor would spin, and the engine would turn over.

I'm with Timmy2 and mreid, check that you have power at the green wire when the key is turned. If so, then connect to terminal 50, not 15a, and you should be good to go.

[Uwon]

Originally Posted by ossiblue

The connection from the bottom bolt to the starter is the power feed to the starter from the large bolt above it where the battery cable is connected. It is not a ground connection. When the solenoid is energized by the connection to terminal 50, the two bolts you see are connected together inside the solenoid--that's what makes the motor run. If you shorted the two bolt terminals with, say a large screwdriver, the motor would spin without engaging the flywheel. If you shorted the top bolt terminal with the spade connector on terminal 50, the solenoid would engage the flywheel, the motor would spin, and the engine would turn over.

I'm with Timmy2 and mreid, check that you have power at the green wire when the key is turned. If so, then connect to terminal 50, not 15a, and you should be good to go.

Thank you, thank you!
This gets back to grade 9 physics and generators and the like. Jogs my memory about armatures.

I'm going to take this one slow as obviously I have misdiagnosed time and time again.
I will first do as Dennis (timmy2) has suggested and do the test across the two main terminals of the starter as you have suggested.
Will then report over the weekend.
A dog's breakfast but I'll get over it.
Cheers,
Johan

[Uwon]

Well, this is fun!!
Starter Motor operates when putting a screw driver across the two big terminals.
checked relay and it works properly, provides 12.6 volts to the green wire leading to the starter solenoid.
Solenoid clicks but does not get the motor going.
Checked for good ground.
Engine turns freely, pulled the lower plugs just in case.
Tried to give the Starter a couple of wacks with a piece od wood and mallet.
Still no go.
Any bright ideas, anyone?
What is the best way to pull the starter out? Can't seem to get enough leverage to undue top bolt.
Please weigh in.
Cheers,
Johan

[ossiblue]

Sounds like your ran all the tests. Motor runs with direct jump to power, solenoid clicks with power, but won't engage the starter or engine. That leaves only a bad solenoid--either the electrical connection or the drive gear isn't fully extending.

[yelcab1]

Either a partial drop, or a bear hug with a long allen socket (round end) will get the top barrel nut.

You need a new starter.

[Uwon]

Starter problem finally solved. Sticky solenoid which was replaced along with a thorough going over. My old solenoid had only one spade connector whereas the replacement solenoid has two. you have to use the top spade (i.e. the one on the right side in the pic below) to activate the solenoid. Don't know what the lower one is for.


So, my next issue is that when I put in the relay for the A/C located in the smuggler's box and I turn the ignition to the ON position, it activates the starter. Ugh! Without the relay installed, the starter only activates when I turn the key to the START position. See relay which came off the donor crashed car.



I thought that perhaps I was mixing up the wires so I retraced using the Bentleys manual. The wiring diagram for the '86 (donor) does not identify the relay terminal numbers but the one for the '85 does and since the diagrams appear to be otherwise the same I followed the numbering and wiring color code. Here are the diagrams for both years.




Can somebody please explain to me how this relay works in particular the relationship between terminals #85 which is live when the ignition switch in in the ON position thereby presumably feeding #86 and hense the starter, and #86 which is live when the ignition switch in in the START position. Do note that #85 is fed directly off the starter yellow wire. Any words of wisdom would be helpful and suggestions on how to narrow down my issue would be really helpful. Thanks in advance.
Cheers,
Johan