The V8 Owners Forum -

hello all,

To add to my misery with trying to get my v8 westie running.

I stupidly left the ignition on overnight.....

The battery was totally flat, but managed to re-charge it back to the norm.

But the car only turns over now and wont run.

Looks like the injectors are no longer firing.

Anyone got an idea what i might have goosed.

Fuel pump runs, and turns over thats about it.

Just worried i might have melted the ecu overnight.

thanks

scott richmond

check the coil as you may of burnt it out.

Presumably you have also tried disconnecting battery to reset ECu and reconnecting - 30 seconds normally does it

Ian

You should never leave the IGN on in a single coil motor.
You'll have goosed the coil for sure - cheap to replace mind

hello again,

Well suprising the coil checks out ok, and i have spark.

But the power resister pack is getting red hot....so hot in fact that it melted all the soldered joints inside.

So i removed the power resister pack cleaned it up and resoldered all the joints back together again.

Resistance of the power resisters still checks out to about 6.4 ohms, so i think this is now ok.

What i orginally thought was the injectors not firing, i since have found out that the injectors are firing constantly when the ignition is turned on....and 12v is constantly supplied to the power resister pack when ignition is on.

This will only stop then either the main relay or ecu is disconnected....also when the ignition is turned off there is still a 0.170mv reading on the voltmeter.....

So me thinks the ecu has gone...or the main relay has siezed.

any thoughts

scott

Have you tried power off the ECU and back on?

It can reset after a surge

Is it hotwire?

I have a chipped ECu to try but the fuelling will be wrong for MOT

Ian

are you sure the injectors are stuck open? There is supposed to be a constant 12v at the injectors as it is the ground that is switched.

hiya,

I have a flapper type and i think the power resisters are supposed to turn the 12v in to 3v at the injector.

At the moment even though the power resisters check out ok at 6.4ohms.

When i measure the voltage at the injectors i get a constant 12v reading, when i turn the ignition on and the power resister pack gets very hot.

If i open the throttle plate with the ignition on i can hear a spraying sound, so can only presume the injectors are fully open from ignition turn on.

Me thinks the ecu has gone.

I removed the ecu yesterday and carely opened it....everything looks fine and could'nt smell any burned components like you might expect if i had burnt it out.

So still looking for answers.

thanks

scott

A resistor doesnt drop voltage it drops current. It only drops voltage when the circuit has reached its designed limit. I would say the fact you have 12v at the injector means they aren't drawing power. That's the theory anyway.

Are you measuring the voltage between the two pins at the injector? If you are then you have a problem. Is this the same on both banks of injectors? Try unplugging the ECU and test, if you still have this then you have a short in the loom. Measure resistance of the injector ground to ground with the ECU unplugged (should be high) with ignition off.

If you measure between both pins at the injector and you don't get voltage then you may have a short on the 12v supply side. This would run your resistors hot and there wouldn't be enough power left to operate the injectors.

If they are open then you will have loads of fuel pouring into the engine which will be very easy to detect.

This is one of those things that takes seconds to check but ages to write down properly am afraid so if the above doesn't make sense you you I will make a better effort at explaining it to you.

Hi Scott
If the earth is floating (ie the ECU is NOT firing the injector) the injector supply will be at 12V, the resistors current limit the injectors when the ECU switches the injector earth to ground when the injector is fired. Yuo really need to look at what the ECU side of the injector is doing, is it switching the injector earth to ground) dont think you will see this without an oscillor scope though. The qiuckest way would be to either borrow a spare, or get the one you have to a tester.
Mike

hiya all,

Yes looks like my ecu.

So its off to the ecu doctor for a test, for £30 at least i can either rule it out or get it fixed.

just depends how much the final bill is.

As i may look to replace the whole flapper efi with a hotwire system, if i can find one.

will let you know what happens when i find out.

thanks everyone

scott

Some thoughts:
When you say you can hear fuel, are you sure you aren't hearing the fuel circulating through the fuel rail, or the 9th (cold start) injector firing?
Does the noise stop if you unplug all the injectors.

OK, now this is how it works:
The injectors always have 12V on one connection. This comes from the main relay. The other side goes to the resistor pack. The resistor pack reduces the current in the circuit by dropping voltage across it. The current is the same through all points in a circuit. The resistor outputs from four injectors are then connected together and taken into the ECU where a big transistor connects them to ground.

When the injector is not firing, the transistor is in the off condition in the ECU, and so every point in the injector circuit will measure around 12volts. Both sides of the injector, and all the connections on the resistor pack.

When the injector is firing, there will be 12volts on one side, around 8-9 volts on the other, 8-9 volts on the yellow wires going into the resistor pack, and 0volts on the big brown wires coming from the resistor pack to the ECU.

And to another comment about coils - leaving the ignition on is only a problem with a points type distributor. It is not an issue with an electronic ignition.

You can see if the injector circuits are working easily by turning on the ignition and then rapidly opening and closing the butterfly. This triggers the enrichment process which makes all the injectors pulse, which you can hear. This works even with the engine not running (but the ignition on)

Chris.