Classic Alternator Issues

[PeterAllen]

Hope someone can guide me on this one.
I have replaced my Alternator and when installing mistakenly connected the wiring for the tacho to the wrong connection point. When I tried to start the car I have shorted something out but can't seem to find what.
Car won't start, I have spark at the coil. The tacho wire seems to go to the coil +ve terminal but I could be wrong on this as it is the same colour as a bunch of others that run through the same harness. The haynes manual for the wiring doesn't show much and haven't been able to track down better wiring diagrams. The car is a classic EFI 1987. The ignition amplifier is under the coil and not on the distributor. Any assistance would be appreciated.

[bee utey]

Hope someone can guide me on this one.
I have replaced my Alternator and when installing mistakenly connected the wiring for the tacho to the wrong connection point. When I tried to start the car I have shorted something out but can't seem to find what.
Car won't start, I have spark at the coil. The tacho wire seems to go to the coil +ve terminal but I could be wrong on this as it is the same colour as a bunch of others that run through the same harness. The haynes manual for the wiring doesn't show much and haven't been able to track down better wiring diagrams. The car is a classic EFI 1987. The ignition amplifier is under the coil and not on the distributor. Any assistance would be appreciated.
What is the tacho wire doing at the coil +ve? There should be a white wire with a black trace at the coil -ve, that is how your computer reads firing pulses. The tacho is a white/grey trace wire connected to a special field terminal at the alternator, and has nothing to do with the running of the engine. The brown/yellow trace wire is the charging bulb wire to the dash, should be connected at the alternator field.

[PhilipA]

Ouch.
The wire to coil NEGATIVE is the wire that tells the ECU that the engine is running and the revs.

By connecting to the positive you have either burned out the diode which is in series or you have damaged the ECU.

Maybe check if the diode is open circuit and if it is replace. Otherwise see if it starts with another ECU with the wire connected to NEGATIVE.
I think it may be time for an auto elctrician or LR specialist.

.Regards Philip A

[PeterAllen]

Thanks for your info.
Do you know what I could have blown by connecting the tacho wire incorrectly.
Do you have a wiring diagram of where the tacho wire from the alternator goes to?
My alternator only had three wires to connect, The main power from the Starter soleniod, the battery lamp warning light and this tacho wire.
Regards

[PeterAllen]

I ran a test from the Battery +ve terminal to the coil -ve and had a reading of 12.5 volts. Haynes manual said it should be 0.
Why would I be getting spark from the coil if I had stuffed up the ignition module etc.
Where is the diode located and how do you test it?
regards

[bee utey]

I ran a test from the Battery +ve terminal to the coil -ve and had a reading of 12.5 volts. Haynes manual said it should be 0.
Why would I be getting spark from the coil if I had stuffed up the ignition module etc.
Where is the diode located and how do you test it?
regards
The coil -ve voltage is controlled by the ignition amp, it is variable as the engine fires. When stationary the voltage should be the same as the +ve terminal, otherwise you have shorted the coil -ve with something. As you have spark this is not the case. Did you read your voltage with the ignition on or off?
The diode should be strapped to the loom near the coil. (I think). Read its resistance, should have a low resistance one way and high with the meter leads reversed. It should have the white/black trace wire connected to one end.

[PeterAllen]

I tested with ignition off as stated in the book.
Thanks again for your comments.
Regards

[PhilipA]

Thanks for your info.
Do you know what I could have blown by connecting the tacho wire incorrectly.



Car won't start, I have spark at the coil. The tacho wire seems to go to the coil +ve terminal but I could be wrong on this as it is the same colour as a bunch of others that run through the same harness. The haynes manual for the wiring doesn't show much and haven't been able to track down better wiring diagrams. The car is a classic EFI 1987. The ignition amplifier is under the coil and not on the distributor. An


The tacho wire goes to the "W" terminal on the alternator. It reads from a field of the alternator. If you have a look at the back of teh alternator it should have "W" stamped there.

The ECU engine revs sensing wire goes to the coil negative.


You seem to be mixed up on which wire is which, at least I am .LOL. The tacho wire will be with the alternator loom and the ECU wire should be on the Air Flow Meter loom. ie completely different places.

I am assuming that you have placed the ECU sensing wire on the + of the coil rather than the -.

The tacho wire should not affect anything to do with starting, even if joined to 12v, I think it would just destroy the tacho, but it may have blown a fuse that also controls some other circuit.

The ECU sensing wire on the other hand may have caused problems in your ECU.
Regard sPhilip A

[PLR]

G`day Peter,

The white/slate tach wire goes to the mutifunction unit ( has another name also ) , It is in the binical ( instruments ) .

Not a fan of haynes but do you have above 12volts with ignition on , yep .

The tests for the under coil amp are a little different to the other amps , don`t remember exactly what , have to look in the book if needed .

If your saying you have a good regular spark from the coil lead when the engine is turned over , the amp , ect . should be good .

Take the cap off , hold the coil lead around 3mm above rotor arm and rotate the engine , if you have a spark the rotor will be crook .

What else did you do at the same time you replaced the Alt ? Have you upset something else unrelated ?

Check the wires coming out of the dissy , mostly the connection that runs near where you were working .

Check all the normal things like the fuel pump running a little ( seconds )/relays tripping etc when the key is switched to On /ignition/start etc .

Is it dual fuel ?

Cheers

[PeterAllen]

Thanks for feedback. Just to clarify, I replaced bad alternator with new. Connected the main wire from solenoid and had two small wires (battery indicator and tacho wires). I connected the two small ones to spots I thought looked right. Stupidly did not research the issue, and cranked the car over. It started no problem but noted that the tacho was not registering so decided to swap over the two wires to see if that fixed the tacho. Therein lays the problem. seems that one of these two wires has shorted out something on their circuit. Cant see what could happen from the battery indicator as the indicator light still works but the other is a mystery.
I noted that a fuse had blown in the aux (trailer) but that may have already been blown. Anyway replaced that and still no go.
Will check fuel pump and relay tomorrow and let you know although I am pretty sure its getting fuel as I could smell fuel when cranking.

Regards to all for your assistance so far.

[PLR]

G`day Peter ,

without knowing which wires you hooked where it`s a bit arkward .

I know you know the N/Y Brown,Yellow and the W/S White, Slate from the Alt do you know the colour you hooked them to ?

Do you have spark at the plugs or is it getting too much fuel ?

You need to narrow down if a spark or fuel problem i think and then look at what is related , because you can smell fuel either is possible , i guess .

Cheers

[PeterAllen]

Hi Guru's ,
here is a bit more info.
The new alternator has a + post which I connected the starter solenoid wire to. Next to it is a spade connection labelled Aux. This is where I connected the tacho wire in the first instance and the battery lamp wire I put on a spade connection labelled ND. With this set up the engine started but I had not reading on the Tachometer. I then changed the tacho wire over to the ND labelled post and the battery lamp wire to the Aux. Went to start and thats when problem was created.
The alternator has a Post connection labelled V and there are two other larger spade connections labelled + next to each other and located in the same area as the ND connection. These three connection points are within some sort of recess for a plug fitting perhaps. The old alternator was an Ingrams and the tacho wire was connected internally to it. The new one is a no name from TR spares.
The tacho wire (white) and the batterylamp wire(brown) go to a plug with two other wires (an earth and oil sensor wires). These run into a loom with a whole bunch of others and I assume run into the dash binnacle. There is no connection with the coil as originally thought.

The test carried out on the coil was with ignition off and connecting between coil -ve and battery +ve I get 12.5V. With ignition on I get 0.1V. Haynes says it should be 0 with ignition off but I am sceptical about this. IS this right?

Regards

[PeterAllen]

Spoke to TR Spares this morning and they advised that the ND connection should be IND and is for battery lamp, The V should be stamped W and is the post to connect tacho.
So now the mystery is what has been upset by me connecting the tacho wire to the IND post. I am beginning to think the problem may have nothing to do with this misconnection as both wires go to the dash binnicle and I havent blown the bulbs. Can't see how that could impact on the starting system at all.
Regards

[bee utey]

The voltages are correct enough, 0.1 volt is small for cable loss. Wouldn't even read on an analogue meter which is what the haynes article would be written for. Now forget the alternator. How the alternator is connected shouldn't affect the starting. I would rather suspect you have dislodged a wire or plug between the distributor and the coil. Look at the cable that connects the distributor to the coil/amp. Is it plugged in? Is it damaged? Test for spark, crank engine with the coil lead out, bend a wire clip to connect inside the coil post. Arrange a 12mm gap to the bracket, crank engine, and watch for spark. Don't touch while cranking.

If your cranking is slow, find a battery charger.

Forget measuring from the battery +ve. Any voltage should be present relative to engine earth. With the ignition on there should be 12 or more volts at the coil +ve. Also at the coil -ve when not cranking. This only shows you haven't shorted the coil -ve. It does not tell you that the ignition amp is working. It will only work when it is all connected.
Make sure as posted before that the white/black trace wire is at the coil -ve. If everything is present and correct the amp may have coincidentally died on the same moment. Rare but not unheard of.

[PeterAllen]

Thanks Bee utey, I won't have a chance to get under the bonnet until Saturday so will post an update next Monday.
Thanks for your assistance.

[PeterAllen]

Here's the update,
Reconnected the alternator, checked for spark and had nothing from the main lead from the coil. Changed the coil and all is good. However, I believe there is a problem with the lead as well, so for the moment the car starts.
With the continuous saga of woes, I drove the beast no more than a kilometre and now the indicators have stopped working. I swear this car is jealous of the P38 we purchased not long ago. Always doing something to get attention.

Thanks to all for your feedback and assistance.