Electronic ignition fault

[morzov]

Got a strange problem starting my van -its a 2.0 Aircooled with electronic ignition set up. I know a little bit about this but would be grateful for your views/advice.

Recently its been running OK but have had problems starting it. Sometimes starts OK and other times just won't start at all.

When it wasn't starting the other day I got a mate to turn it over and I pulled the king lead off the distributor and there was no spark. I've since changed the coil and hall sender for one's that I know to work but there is currently no spark although bizzarely the van did start this morning.

There is 12v at the battery and 12v at the +ve terminal on the coil but still no spark. I've gone about as far as I can with this so would be grateful for any ideas.

Cheers

[kevtherev]

A poorly earthed coil will do this.
it is found near to it or behind it.
Also the ECU will allow this to happen, if the contacts are suspect or the ECU is failing.

[morzov]

A poorly earthed coil will do this.
it is found near to it or behind it.
Also the ECU will allow this to happen, if the contacts are suspect or the ECU is failing.

Thanks for the reply.

It did start earlier this evening but as that has happened before and I don't think its cured.

How is the coil earthed - there are 4 wires coming into it - from memory 1 to the -ve terminal and 3 to the + terminal. Is it one of those?

Presume the ECU is the Hall sender unit? I did put a new one in (at least the part which is screwed to the engine bay wall but that didn't make any difference)

Also could it be possible that the battery is a bit weak and is therefore not consistently providing a strong spark at start up?

[kevtherev]

yes it's one of those 4 wires
the hall sensor looks like this, is this what you replaced?




Does your engine have vacuum advance?

[kevtherev]

this is with the vac advance.

you may even have a failing plug problem to the distributor, it's happened before on here.

No spark at the king lead is a faulty Hall sensor, but try a good one before you buy new.
This sensor triggers the ICU which tells the coil to spark
What you replaced in the engine bay was the ICU

[morzov]

Yes my van has vacuum advance.

Didn't replace the item you pictured. I may have got the terminology wrong - I replaced the Hall Generator - think that's the right term, anyway looks like this:
http://www.intermotor.co.uk/index.html? ... m4g3r79mf3" onclick="window.open(this.href);return false;

This is where my limited knowledge of electrical systems comes in but does the spark come via the coil first or via the distributor. I have been assuming the former and I did check that 12V was getting to the plug that goes into the Hall sensor in the top of the distributor.

[ghost123uk]

Didn't replace the item you pictured. I may have got the terminology wrong - I replaced the Hall Generator - think that's the right term, anyway looks like this:
http://www.intermotor.co.uk/index.html? ... m4g3r79mf3" onclick="window.open(this.href);return false;

What you replaced in the engine bay was the ICU

There is your answer

[@ Kev = ICU or ECU, just different names for the same thing ? , or a typo]

As Kev says, the hall sensor is in the distributor (where older vehicles had their points) and connects via the little plug on the side. Again, Kev is right, change that and check the wiring around the plug that goes into that socket on the dissy (wiggle the wires whilst it is running). Both the hall sensor and that plug / wiring have been known to cause problems like yours.

This is where my limited knowledge of electrical systems comes in but does the spark come via the coil first or via the distributor.

Via the coil first, but "triggered" by the bits in the main body of the dizzy =

The hall sensor is a magnetic pickup, there is a tiny magnet attached to the spinning distributor shaft. As this magnet passes the hall sensor it sends a pulse of electricity to the ECU (that box you bought) this then sends another pulse to the coil which produces a spark (on the king lead). The distributor then "distributes" this spark to the appropriate spark plug lead, determined by the position of the rotor arm.

[kevtherev]

ICU... ignition control unit
ECU...engine control unit

mine is less confusing as we don't have variable valve timing and knock sensing in our ECU's or should that really be PCU's as it's more commonly known

[morzov]

Thanks to both for the replies - that's been a great help.

I think I have a better understanding of the system now and am going to go and take a look at the unit on top of the distributor - whatever its called !

[BOXY]

The hall sensor is a magnetic pickup, there is a tiny magnet attached to the spinning distributor shaft. As this magnet passes the hall sensor it sends a pulse of electricity to the ECU (that box you bought) this then sends another pulse to the coil which produces a spark (on the king lead).

This isn't right but the theory is.

The magnetic pickup is fixed in the body of the distributor. The rotor attached to the distributor shaft (the big metal dish thing with the four slots around the edge) is stainless steel so non magnetic. As the rotor goes around the solid part blocks the magnetic switch doing the same thing as points opening. When the gap passes the pickup the magnet can do what magnets do best and close, switching the power back on.

[ghost123uk]

Just keeping it simple as poss