Checking dual ignition circuit

[Guest]

Being the spanner-wielding petrolhead that I am, I'm coming to the end of doing the 12 000 mile service on my 993. Thoroughly enjoyed it so far [8D]

Does anyone have any experience of the best way to check the dual ignition circuit? One option is to simply remove the lower distributor cap & check that there is resistance to moving the rotor arm, but this only confirms that the belt is working & not the coil.

What about disconnecting the low tension supply to the upper coil/distrubutor, then doing same to lower? If engine runs each time, this would confirm operation of each system.

Will I cause damage if I disconnect one of the LOW tension circuits? [8|]

Thanks, Roddy

 

[burrow01]

ORIGINAL: roddylennox

Does anyone have any experience of the best way to check the dual ignition circuit? One option is to simply remove the lower distributor cap & check that there is resistance to moving the rotor arm, but this only confirms that the belt is working & not the coil.

What about disconnecting the low tension supply to the upper coil/distrubutor, then doing same to lower? If engine runs each time, this would confirm operation of each system.

Will I cause damage if I disconnect one of the LOW tension circuits? [8|]

Thanks, Roddy

What I did was pull the center HT lead from each distributor, and start the engine - if it does not start, that circuit would not be working - don't think this will cause any potential damage, and it's easy to do

Pete

 

[38F3E1]

ORIGINAL: burrow01

What I did was pull the center HT  lead from each distributor, and start the engine - if it does not start, that circuit would not be working - don't think this will cause any potential damage, and it's easy to do

Pete

Same works on the 964 and 993 and is a simple test to see if each circuit is working. Turn off car, remove center lead from cap, start, turn off. Repeat for other cap. Don't run it for long as if it's not working it's obvious as the car will not start.

DO NOT pull the leads whilst the car is running. You will possibly KILL yourself if you do as the 993 runs a very high voltage system.

Ian.

 

[Guest]

Thank guys.

So if I don't have a Hammer, what about the low tension idea...better for the coils' longevity to test them this way? [8|][8|][8|]

 

[Guest]

Maurice, you're a star. Thanks (again) for clarifying the technical side of this.

Would be great to have a Hammer...[8D]

Roddy

 

[t11ner]

Just a thought here fellas.

If you remove the coil lead from one cap and run the engine, you are sending circa 50k volts up a lead with no earth to safely return to. If you have any flaws in the insulation on the lead or coil tower this leaves the possibility of it arching across to one of the low voltage terminals on the coil and going straight back up the wire to the ecu. This would very likely pop the ecu [&:].

I don't know the details of this system but I'm guessing that it's not capacitive discharge like the earlier 911s and that it is running a fairly conventional method of triggering the coil, in which case my preference would be to disconnect the low voltage terminals on the coil and avoid the spark being made in the first place. On a conventional setup having the circuit disconnected will do no harm although it may log a fault code, particularly on later models of car.

Steve H

 

[Guest]

Thanks Steve. Now I'm more confused than ever!

Think I'll ask the guys at 9M when we lucky folks from R5 up 'ere in the North West visit them on Wednesday this week.

Roddy

 

[Guest]

ORIGINAL: MoC2S
Roddy, would you do me a favour, remind Colin that I need prices / numbers for the Dyno Runs at the Engine Seminar .. a couple of emails have elicited no response .. [&o]

No problem Maurice, will do []

 

[Guest]

Hi Maurice, have emailed you.

Regards,
Roddy

 

[Guest]

Perhaps the bottom line on this...

Robin (top notch mechanic++) at 9m told me should be fine to take either HT coil lead off if only running the car for a few seconds to check each circuit. Obviously you need to do this before starting the car & not whilst it's running!

Might put this one to rest then, for those of us who don't have Hammers.

Roddy[]