No spark, suspect hall sensor?

[Jimaroid]

Does this sound like a correct diagnosis?

The problem I've been having is that our 1.9DG engine recently cut out whilst driving happily. Initially it seems to have been caused by a failed ignition coil as we found the insulation on + terminal wire had obviously overheated. Took the coil off and when measured the resistance of the primary and second circuit in the coil were way out of spec (3.3 ohms and 5.3 Kohms). Sourced a new coil that's in-spec and fitted it along with a new ignition amplifier.

Good charge in the battery and engine will crank fine but there's still no spark at the plugs. Have tested with a known good spark plug against the engine block and see no spark. Have tested the HT leads and resistance all seems correct.

Next I've pulled the king HT lead and hall sensor connector, then jumped the green/white (centre) wire in connector and I see a good spark from the king lead to engine block which I believe means the ignition circuit is good and the hall sensor or its wiring may be suspect.

I've tested the voltage across the wiring to the hall sensor and I'm getting about 4.5 volts on green/white centre wire but only 10.5 volts on the red/black wire. Is this wrong, shouldn't the red/black be more like 12?

From all this it seems the hall sensor has failed? Does that make sense? Anything else I should do or try?

[bigherb]

but only 10.5 volts on the red/black wire. Is this wrong, shouldn't the red/black be more like 12?

No as long as it is more than 5V (it is usually around 11V), you should check the voltage across the red/black and brown/white wires which will also check the Hall sender earth.

[Jimaroid]

No as long as it is more than 5V (it is usually around 11V), you should check the voltage across the red/black and brown/white wires which will also check the Hall sender earth.

Thanks, I'm seeing 10.3V between red/black and brown/white with connector disconnected and 9.9V when it's connected.

[bigherb]

That's alright then.

[Jimaroid]

That's alright then.

So, power looks correct therefore probably hall sensor at fault?

[300CE]

Do you have anyone local who you can swap a dizzy over with? I had the same symptoms where there was no spark, but then it would be ok, but she'd sometimes back fire like a good un'. I pretty much changed everything electrical with new to no avail - then bought a second hand dizzy and she's been fine since.

My assumption is that it was the hall sender and I've kept the original dizzy and will change it one day.

If you can borrow one and it runs fine, you've sorted it.

[Jimaroid]

Progress but a little confused now as I think I've answered my own question. Took the dizzy off the engine , wired it up and turned the boss manually and I get a good spark at the plugs no problem. Not what I was seeing when cranking on the starter and means the hall sensor is fine. Need to reassemble and crank the engine on the starter again but it's getting late and I don't want to annoy the neighbours. I'll try again tomorrow.

Thanks for the help so far.

[nicq]

Progress but a little confused now as I think I've answered my own question. Took the dizzy off the engine , wired it up and turned the boss manually and I get a good spark at the plugs no problem. Not what I was seeing when cranking on the starter and means the hall sensor is fine. Need to reassemble and crank the engine on the starter again but it's getting late and I don't want to annoy the neighbours. I'll try again tomorrow.

Thanks for the help so far.

Make sure you have no short to gnd in the distributor it won't show with the dizy out

[Jimaroid]

Last part of the mystery solved - a worn out ignition switch.