Carb - idle shut off valve

[what2do]

Just fitted a new coil - no difference whatsoever. Still no spark at the King lead. Checked both the new and coil, oddly I'm getting the same readings of 3.06 ohms across all 4 points on the 2 coils. Noticed that my meter only goes down to 200 ohms, could this be why it's not registering the lower of the values? Why is it registering the same resistance across both the primary and secondary? Rhetorical really as its not the reason the engine isn't running. Next step is to test the dizzy output, correct?

Ps. With the new coil, I then reconnected the live lead from the alternator to the coil to see if it made a difference - nope.

Thanks in advance.

[itchyfeet]

I'd be looking at leads next then ignition amp and dizzy last
in order of reliability.

your multimeter goes lower than 200 thats the zero to 200 range

you need to move it to the Kohm range to measure higher resitances

or get an autoranging multimeter it would have saved you the price of a coil

[what2do]

I'd be looking at leads next then ignition amp and dizzy last
in order of reliability.

your multimeter goes lower than 200 thats the zero to 200 range

you need to move it to the Kohm range to measure higher resitances

or get an autoranging multimeter it would have saved you the price of a coil

I'll be returning the coil to ECP, I asked for Bosch and was told it would be. Upon collecting it, I demonstrated that it was clearly not a Bosch only to be told that it was a Bosch equivalent. I commented that I had two legs with feet at the end but that didn't make me a Mo Farah equivalent!!!

I await instructions on testing the ignition amp as I don't have any voltage at the hall sender plug. Around and around I go but at least I'm learning.........

[CJH]

My apologies if you've already said and I've misunderstood, but where did you take the new live feed for the coil from, and does it measure +12V with respect to the earth tag *on the coil* when the ignition is on*? I know you've said you cleaned up the earths, but you didn't say which ones, and it's still feasible that the coil isn't earthing properly.

* There's even a remote chance, depending where you've taken the live from, that it could be live with the ignition on, but dead when the starter is turning, if you've taken it from the X circuit by mistake.

[what2do]

My apologies if you've already said and I've misunderstood, but where did you take the new live feed for the coil from, and does it measure +12V with respect to the earth tag *on the coil* when the ignition is on*? I know you've said you cleaned up the earths, but you didn't say which ones, and it's still feasible that the coil isn't earthing properly.

* There's even a remote chance, depending where you've taken the live from, that it could be live with the ignition on, but dead when the starter is turning, if you've taken it from the X circuit by mistake.

I've taken the live feed from the stud on the alternator where the red cable(s) attach. And then connected it to the terminal where the black wires fix on the coil. I put my meter on the alternator stud and to the clean flat surface on the block where there is an Earth at present (I'll need to check which earth this is for clarity of explanation), it registered 12.5 V. Should I reattach the live feed and stick the meter probe onto the lug on the coil where this attaches and measure again?

Thank you.

[CJH]

OK, I've just caught up on your Hall sensor thread, and there's some overlap between my post and BigHerb's advice. I'm suggesting you check for +12V between the two spade connectors on the coil - one is the live terminal (black wires, pin 15), and one should go to earth (pin 1, possibly green). I think that's right. If you just check for 12V difference between pin 15 and the engine it doesn't check whether there's a fault in the coil earth wire.

[what2do]

OK, I've just caught up on your Hall sensor thread, and there's some overlap between my post and BigHerb's advice. I'm suggesting you check for +12V between the two spade connectors on the coil - one is the live terminal (black wires, pin 15), and one should go to earth (pin 1, possibly green). I think that's right. If you just check for 12V difference between pin 15 and the engine it doesn't check whether there's a fault in the coil earth wire.

So, just to get this straight; test 1, with everything connected as original, check for 12V between the two points on the coil (spade connectors) with the ignition on. Test 2, do the same but detach the black wires from the coil and put the live feed from the alternator.

Correct? I'm not worried about sounding like an idiot if it means that I test correctly and report back the proper findings. Many thanks.

[CJH]

Yes - your connection from the alternator is fine for testing purposes, but as that's a permanent live it's not really suitable as a long-term replacement for the original black wire. If the earth on pin 1 is bad, then neither of those tests will show the required +12V, so another test would then to be to check for 12V between the original black wire and a known good earth. If that shows +12V then it also points to the earth being bad. I suppose an even easier test is to measure continuity between pin 1 and a known good earth.

[what2do]

Yes - your connection from the alternator is fine for testing purposes, but as that's a permanent live it's not really suitable as a long-term replacement for the original black wire. If the earth on pin 1 is bad, then neither of those tests will show the required +12V, so another test would then to be to check for 12V between the original black wire and a known good earth. If that shows +12V then it also points to the earth being bad. I suppose an even easier test is to measure continuity between pin 1 and a known good earth.

Thanks, I'll be back in 10 minutes.

[what2do]

Ok. Checked for continuity between the spade connector on the coil where the green wires attach and the surface previously mentioned on the engine bay - resulted in a very clear audible buzz. Then tried to find a voltage from the black wires off the coil (I tried both the connector with the single wire and the other connector with two wires as I'm only half certain the single wire is the feed), using the same flat surface on the engine as I've tested it several times and it appears good. This resulted in absolutely nothing. I did then notice that the female spade (black wires) connectors with filthy and green, should I trim them back to good copper and then measure again?

[CJH]

Hmm - well that contradicts what your RAC man said. Didn't he say there was no live feed to the coil? That black wire that appears good (I assume by that you measured +12V) IS your coil live feed.

You do seem to have eliminated problems with the low tension coil circuit now, but I still can't see that you've checked for the voltage across pin 15 and pin 1 (your separate tests show that this should be ok, but maybe it's an accumulation of things)

As for the corrosion, the black wire carries about 8A I think, so it would have to be pretty bad to stop that current. Nevertheless, digital voltmeters can measure voltage even if the current carrying capacity is compromised - so it might show 12V on the meter but drop to much less when trying to carry 8A due to high resistance. I think you'd notice it getting hot after trying to start the engine if that's the case. Could be worth a good clean up I guess. Do you have an unwilling assistant to turn the starter for you so you can watch the voltage on pin 15?*

*Wait - if the symptoms are the same with a good new live feed from the alternator then the corrosion in the black wires probably isn't significant.

[what2do]

Hmm - well that contradicts what your RAC man said. Didn't he say there was no live feed to the coil? That black wire that appears good (I assume by that you measured +12V) IS your coil live feed.

You do seem to have eliminated problems with the low tension coil circuit now, but I still can't see that you've checked for the voltage across pin 15 and pin 1 (your separate tests show that this should be ok, but maybe it's an accumulation of things)

As for the corrosion, the black wire carries about 8A I think, so it would have to be pretty bad to stop that current. Nevertheless, digital voltmeters can measure voltage even if the current carrying capacity is compromised - so it might show 12V on the meter but drop to much less when trying to carry 8A due to high resistance. I think you'd notice it getting hot after trying to start the engine if that's the case. Could be worth a good clean up I guess. Do you have an unwilling assistant to turn the starter for you so you can watch the voltage on pin 15?*

*Wait - if the symptoms are the same with a good new live feed from the alternator then the corrosion in the black wires probably isn't significant.

I think you may have misunderstood my findings, when testing the black wire to the coil, there was 0V.

Above I used the phrase 'it appears good', is this what lead you to believe I had 12 V? I meant that the earthing point was good. Apologies if this is the case.

[CJH]

Ah yes, I misunderstood. Ok, so the RAC man was right then. So with your temporary live feed from the alternator connected to pin 15, you should see +12V between pin 15 and pin 1 (ignition does not need to be on, as your alternator feed connects directly to the battery).

That dead black wire needs to be investigated too. I think it comes from the fuse box, so it's possible you've knocked it off. I think it reaches the fusebox via the ignition switch - unfused as far as I'm aware, but I'm basing that on a more intimate knowledge of my mate's beach buggy than my van's wiring. As said though, even with a lot of corrosion a digital multimeter would probably register a voltage if it was connected.

I think in summary, if you've got 12v between pin 15 and pin 1 using your temporary alternator wire (which you should have, based on your earth continuity test) then you can probably move on from the coil wiring!

[what2do]

With the temporary live feed to the coil in place, I have measured between 15 and 1 - OV

Checked the earths repeatedly for continuity, checked the metal strap around the coil, checked the bolt head and washer that screws into the body - lots of buzzing. Even with my limited knowledge I'm baffled as to why I'm not getting 12 V through the coil.

And onto the next step......

[CJH]

With the temporary live feed to the coil in place, I have measured between 15 and 1 - OV

OK, I don't understand that - if pin 1 shows continuity to earth, and pin 15 (rather than the disconnected cable from the alternator) measures 12V with respect to a (different) good earth, then I can't see why you don't get 12V between pin 15 and pin 1. This seems to be a contradiction.