Electrics.
Turbo Mini Forums

I have a very weird problem, as is usually the case with electrics from reading about other peoples issues with them. I think, I have traced the problem to the plug on the altenator, specifically the signal wire to the altenator.

The Altenator goes on and off charge at will, I have a voltmeter on the dash and on the ECU so I know both of these are correct as they have the same reading. Im getting usually about 12.5V on charge, this is with just the engine running, no other electrics on, which Id love to use as Ive a fair amount of ICE in the car, but keeping the engine going is my priority!.

The warning light on the dash illuminates when Ign is switched, and *sometimes* goes off. From here we way see a full 14 volts on the voltmeter or 12.5 depending on what the altenator feels like. During driving, the warning light goes dim, off, bright, dim, it usually stays either off or dim.

This has me thinking Ive a Issue with the signal wire, as I understand this is part of the circuit that the warning light is on and if its not working right the field windings on the altenator are not being energised, and hence no power. Obviously the other option is the altenator is useless(wouldnt mind as then I can fit a nice denso one :) ).

Other issues possibly related, well one is definatley related. When the voltmeter gives 12.5 Volts, on charge but just about, the engine Idles grand. Once the altenator knocks out 14 or so volts, the engine will not idle, it just cuts out unless I keep the accelerator featherd, TPS reading is 1- 2%.
So this issue is definatley related as the higher voltage is causing issues with the sensors or ecu.

Second I have no Idea, the fuel tank guage has a mind of its own, It will be empty, half full, full then empty, usually empty lol, its caught me out once when I ran out of petrol, I put it down to me being dumb and ignoring the guage as wrong as using that guage im getting fairly bad Fuel economy. The Tank is a MPI job, with a sender from a carb mini.

Any Ideas? Do I need a capacitor or something to smooth out all the fluctuations?

I dont know what the rest of the problem is but I suspect the alternator is faulty.

What I am pretty sure of is the the engine stalling when the alternator decides to provide full output is just the. load it then puts on the engine.

Its the same effect on my car when the electric fan cuts in - it drops the tickover speed.

Humm, I dont want to go replacing the altenator unless its the problem, which I dont think it is as it is producing 14 volts intermittantly, sometimes for hours at a time.

Is there a Voltage regulator on the Lucas Altenators?

Yes

Ill go have a look at that so.

Put a voltmeter on the starter battery terminal, one on earth, run the engine at fast idle, and go round wiggling the wiring where the signal wire is routed and see what it says. It could be that the lucar on the signal wire is corroded or fitting loose on the alternator. Or you may have a very small break in the wiring causing resistance. Another daft thing is check the fan belt is free of any lubricants or contaminants, and that its tensioned correctly.Also worth checking the battery terminals are tight and also free from corrosion, that's about all i can think of to check at the moment. If you need to, and if you can, invest in a 70a alternator, haven't regretted buying mine when my std alt. died on me.
Another train of thought, check the connector on the back of the clocks isnt loose or corroded.

Edited by Carlzilla on 4th Aug, 2011.

Hardwire the alternator to the battery with a 3w bulb between the signal wire terminal. Does the alternator charge okay?

ECU - what type is it and how was it mapped?
Are you getting the readings you would expect from the sensors?

Fuel gauge - what are you using and is there a voltage stabiliser fitted and is it the right one for the set up?

On 5th Sep, 2011 Vegard said:
I stand corrected. You should know

I don't think the carb sender will work with a MPI fuel pump in the way. I reckon it will get caught on the pump.

Most if not all programable ECU's have settings for the injector that take into consideration the vlotage.

A fraction of each pulse of the injector is the time the winding takes to generate the magnetic field to start lifting the pintle of the injector. This is sometimes called the 'open time' basically the time it takes for the injector to start to open.

The remainder of the pulse is the time it takes for the energised injector to go from full closed to full open sometimes known as 'ramp up time'

The open time plus the ramp up time is sometimes known as the 'effective ramp up time' which is the time from the point the power is applied to the injector, to the point that it is full open

Cutting a long subject short, the time it takes an injector to open at 12v is greather than it is at 14v. therefore if your injecotr will flow more or less fuel depending on the voltage, for the same pulse width.

If your injector settings do not resemble the injectors you are using and you have tuned your engine at 12.5v, at 14,5v the injectors might flow more fuel than is required, and at idle, it doesnt take much. By feathering the throttle to get your idle better would suggest that at the higher voltage, the engine is starting to run rich.

I know it might have been asked before, but do you have any wide band lambda?