Lucas 9EM ignition module.

What is it out of, what does it do?

It was widely used on British cars, during the 80's IIRC.

Its a transistor assisted ignition, but I don't know whether its points or reluctor.

A couple turned up in a box of auto spares I aquired and it'd be handy to figure out how to test them..

ught

As with all components manufactured by Lucas, the God of Darkness, it's purpose is to function for a non-specified length of time and then fail at the most troublesome moment.

As with all components manufactured by Lucas, the God of Darkness, it's purpose is to function for a non-specified length of time and then fail at the most troublesome moment.

There was much worse than Lucas about - close running for a photo finish are Wipac, Czeckoslovakian and Italian.

Can't remember what it was I had that was Italian - it fell to bits even quicker than the CZ250!

Actually - on reflection, nothing is quite as bad as Wipac!

"ian field" wrote in news:_OxOn.60834$BW1.22398@hurricane:

open one up and examine it. Or is it potted?

I don't think Lucas ever made assisted points systems and all the electronic ones I know are VR.

I think the unit you refer to was mounted on the distributor, and the most likely vehicle it was used on in the US the Range Rover. The connections on the heatsink or mounting plate are to the VR sensor, the other two on top go to the coil. Some later versions had a three pin connector - the extra one for a cable shield.

The unit can be reliable but rather depends on how hot it gets. On vehicles with air con it's likely to have a shorter life.

hought

I'm in the UK, and quite the most unreliable 'car' electrics I've ever had was on a Bedford van - made by Vauxhall, a GM owned company. With Delco electrics. The Delco distributor broke its drive on several occasions. Perhaps GM thought a 4 cylinder engine only needed half the effort to engineer parts for? The starter and alternator both failed too. All in under 50,000 miles.

On Sat, 5 Jun 2010 20:44:54 +0100, "ian field" put finger to keyboard and composed:

Contact points would need significant DC current to wet them, ie to stop them from becoming oxidised. Magnetic reluctor inputs, OTOH, may be AC coupled, ie no DC bias current.

I would hook up a 12V supply and measure the short circuit current out of the input.

- Franc Zabkar

Bosch have taken up the challenge.

Igniton unit failure takes out coil as it fails short so overheats coil. Coil failure takes out igntion amp by short circuit. Which comes first? They all do that sir.

Its potted and backed with an aluminium h/sink plate - notoriously difficult to abrade the filler away without destroying the components.

Thanks - that's more than I knew before.

Years ago I built a MOSFET TAC for a small motorcycle, a scrap 19" monitor donated a 900V/9A MOSFET from its flyback switcher. The TAC used the MOSFET in grounded gate mode (gate tied to +12V) so the full coil current flowed through the points but the voltage at contact break never exceeded the supply voltage, so no arcing and no pitting.

The MOSFET interrupted the coil current very rapidly and eliminated the energy wasted drawing an arc between the points as they break, the engine revved easily to valve-bounce in the lowest few gears, by exchanging a bit of restraint for very impressive revs I could save considerable amounts of fuel.

The downside is that there doesn't seem to be any such thing as a logic-level high voltage MOSFET, so there were limitations due to the cold weather drop in cranking voltage.

You might find this an interesting read:

ght

The following web page has a link to a zip file with information of troubleshooting and testing the Rover/Honda ignition system. It helped greatly in repairing my '91 Honda Civic. It ended up needing a new coil (HT shorted to core). Also make sure the ground screw on the module is tightened to the distributor housing. My module was made by NEC.

That's not the Lucas 9EM, though. And apparently no more reliable. ;-)