512TR starter problem(s)

On some of the '94 512 TRs they used a Nippon starter in place of the Bosch. I don't know if it was a later model change or why they did it, but the starter is smaller and lighter than the Bosch, I believe. On the Nippon, there is no separate solenoid.

 

Can you post a pic and model number of the Nippon unit?

 

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Mel, where did you hook up your connector?

Did you hook to the I connector?

Did you still get this "extra" current when you just tested the exit wire at the F connector?
Did you test the fuse box pin at F1 for extra current? (If so, could the S relay be the problem?)

Although you have solved your problem with your new jumper wire, I still would like to understand what is going on at your F connector.

 

It is the F connector. I posted the circuit diagram so you and others can follow the logic.
At this point, I do not feel we have found the problem. We have only put a band aid on it.

Is anyone else following me?

 

My fault, I still call them Nippon. Originally part of Toyota, Nippon-Denso split from the carmaker and eventually shortened the name to Denso, which means electrical equipment in Japanese. I believe they remain the biggest producer of auto parts on the planet. The unit shown above is correct OEM for my 1994 512TR.

 

Mel-
I had the same problem when I pulled the white wire from the fusebox (IN from the ignition switch) and jumped it directly to the white wire OUT to the starter solenoid. I had to replace the IN wire (still jumped) back into the connector and the fuse box. All works well, but still no start when hot.

 

exactly how did you connect that terminal to always (-)

 

Yes, all functions normally now, except no start when hot (new starter).

I tested the entire circuit yesterday. Several times. Here is what I found:

From battery to ignition switch 12.6 v
from ignition switch to connector H, terminal 1 (white wire) 9.65 volts start, 0 v run
with connector H in place and checking connector F terminal 1: 9.65 v start, 6 v run
connector 50 (under flexible air duct) 12 v start, 6 v run
terminal 20 (unattached from starter solenoid) 12v start, 6 v run
with terminal 20 attached to starter solenoid 10.5 v start, 0 v run

Now how does this make any sense? I can understand a 3 v drop through starter switch (also goes through alarm starter kill which I will soon remove) as this is a 20 year old, 52,000 mile vehicle, but could there be 6 v bleeding back into the starter circuit from the depths of the fusebox, giving 6v in run position?
How can the voltage then jump up to 12 v at connector 50 and terminal 20, and where does the 6 v in run position go when terminal 20 is attached to the starter?

I purchased a new IMI Hi Torque starter (#159-04) and installed it yesterday (it took all of 4 minutes and it fit perfectly) as it seems the starter solenoid is getting 10.5 volts and in case my new starter was the source of the hot start issues. I have not yet taken the old girl out on an extended run, but immediately I noticed this starter was much quieter. I will keep the forum advised

Mel: could you explain step by step your latest fuse box mod?

 

Hi Mel, I don't understand either.
Here is a pic of the neg (white wire) and how it is influenced by the starter circuit.

Even looking at it, I still don't understand it. Can someone chime in to sort it out for me?
Image Unavailable, Please Login

 

Why the H connector?

 

What the 512TR schematic indicates is that they got tricky and intentionally disable relay S (key services) during starter motor cranking (so things like the windows or wipers don't operate when the starter is operating). When you turn the key "on", the B (white) wire from the ignition switch is not +12V and the resistance of the starter solenoid is very low so the B wire is effectively ground = the coil of relay S energizes = relay S closes = the windows, etc. work; however, when the key is turned to start = the B wire is now +12V = both sides of the relay S coil are at +12V = relay S is open/unactuated = the windows, etc. don't work (even if you are asking them to work). After the engine starts, and you release the key back to the "on" position = relay S again closes = the windows, etc. work again.

The problem is if that you remove the B wire completely from the I connector and connect it directly to the B wire in the F connector (to bypass those connections and the fuse-relay panel and make the starter solenoid work more reliably), then relay S always stays unactuated = none of the key service items will work. So if you make this mod (B wire from I connector to B wire in F connector directly) you need to add another wire to keep that one side of the S relay coil connected to the B wires (or leave the B wires in their respective connectors and add an external jumper wire between the two B wires).

 

Thanks for chiming in Steve.

In your opinion, could a problem in the S relay cause a no start condition? (For instance, if it were stuck in a closed position, would the starter still fire?)

Again, thanks for your help.

 

No, the state of the switch inside the S relay would have no affect on the voltage on the B wire network, but IMO, it's a no-brainer reliability improvement for starting to add a (soldered) external jumper wire from the B wire in the I connector to the B wire in the F connector (but leave the B wires in those connectors still connected to the board to operate relay S).

 

No, but don't operate things like the window, wipers, etc. when trying to start the engine (as with your modification, they will operate when trying to start). Instead of connecting that S relay connection to a permanent ground, connect it to where you have joined the B wires together and you will restore the stock operation (while still improving the operation of the solenoid) - JMO.

 

Mel,

I dont think you can get a straight answer as to what the "upgraded" Fuse box will offer.

My thoughts are that it just moves the high amp circuits (AC, radiator fans , and fuel pumps off the board) I did this already for less than $85.

So, I think it is a difficult decision to make.

 

Steve,

If the relay was stuck closed......couldn't the current go through different directions in the fuse board?

Would this also cause the starter to engage with out the key? (Which I believe may have caused problems here)

Sorry for the questions, I am just trying to understand this circuit.

 

If we define "stuck closed" as the switch contacts inside the relay S being welded together, then, no, this wouldn't cause the starter to engage without the key, but, if a metal piece physically broke off inside the relay S and then shorted some of the connections together that would normally never be connected = that could cause the starter to engage without the key (but it might also fry some traces on the PCB after a few seconds as the current to engage the solenoid is kind of large and most of the other traces are not designed for big current).

 

Sorry, NOT "H" connector, I meant "I" connector