Not firing

[witty]

Have power to points but no spark at any of the plugs.

New plugs, coil, leads, condenser. Distributor cap and breaker points look okay and all tests with meter are good. Dwell angle 35, points gap 3.

Had spark one day, next nothing. I adjusted the idle speed up a tad, would that effect anything?

I read about the AAV, should I take it off and clean it, and also should I remove distributor and clean the trigger points?

Totally stumped why I have no spark at plugs. Have worked on many vehicles with HT coil and points systems and never had issues like this before. Does the air filter have to be fitted to start the engine?

All advice will be taken seriously, thanks

[polymathman]

The AAV, air cleaner ect will have no effect on spark.

Troubleshooting is pretty straight forward and by the numbers.
1. Check for voltage to the both sides of the coil, you should get 12v with the points wire disconnected. Reconnect.
2. Check for 12v on the arm of the points when open, with the condenser wire disconnected. 12v.
3. Check as above with condenser connected.
4. Check that the ground side of the points is 0 resistance to the negative terminal of the battery.
All this is the primary circuit.

1. Pill the central spark wire from the distributor cap and hold it a bit away from a ground and crank the engine. Spark. Reconnect.
2. Pull a plug wire and put an old plug in it and ground it. Crank. Spark.
This is the secondary circuit.

Ken

[KenM]

Hi Allen,
I've had problems with points before, they were working fine but I was fiddling around with the dwell, took out the points to give them a file and put them back, absolutley nothing. Couldn't get it to fire no matter how I adjusted them. Put in a new set of points and voila!, all fixed. So I dunno, just because they look ok maybe they aren't, certainly happened to me. Maybe I have the Doulton touch.
Cheers,

[witty]

Thanks Ken

the points are nearly new and have no visible wear at the contacts, have some doubts with the dizzy cap,
Im getting some jumpy readings on the ohm meter from inside to top connectors.
Picked up a good cap and about to try it out, hope it isnt the ICM.

Will let u know

Cheers

[witty]

Polymathman

My power wire (Green) to the points come from the ICM and not direct from coil, this cable has the condenser attached
on manufacture.

I am reading 12V at open points, my test light shows that as well as volt meter, the ballast resistors are true readings, the coil primary and secondary readings are correct.
The coil secondary to earth has good spark, but after installing in cap, no spark at plug.
I think maybe it is the cap, has minute cracks at the top around the screw threads that connect to HT leads, so im trying a good one
I found second hand. Im hoping the ICM hasnt died.

Thanks
Allen

Should i have spark at the points on cranking?

[polymathman]

Although transistor modules change somewhat the electronics, the principles remain the same.

Old school had the points handling the voltage from the coil, and there would be a small spark. This would cause the contact points to oxidize rapidly and lead to pitting and loss of efficiency. Transistorized systems only use a very small current which causes no harm to the points, as it is used simply as a switch to trigger the module. So, no spark at the points.

If you are getting spark at the coil wire and nothing at the plugs, then you know that the primary circuit, plus the coil, are OK. Then it has to be the cap, rotor or the spark plug wires or the spark plugs.

Good job, keep us posted!
Ken

[witty]

ken

tried new cap and fired up after some nudging, sounds like running on 5 cylinders tho.

I think i need to check if the leads are set right, maybe i have the firing order wrong.
Too dark now and had enough, will start in the dark later and check for arching.

Don't ever buy Eagle HT leads, the cap connectors are weak as ****!

at least I have spark again

Thanks guys

Will post progress report asap

[witty]

Hi guys

You wont believe this, the rotor has no resistance or continuity at all, and it is the wrong one.
It is listed as a GB778, which is for w123 or w126 models, according to the Bosch parts listings.
My model is listed as GB779 (ordered from Bosch)as well as installing new breakers. Some cowboy has played shortcuts here.
Im hoping after removing distributor and thoroughly cleaning it and the trigger points I will see some results.

Waiting for rotor now.
Thanks
Allen

[witty]

Hi all

Good news, installed the distributor with new points, rotor etc. Have strong spark now.
Starts first turn and running great, I believe the rotor was the problem plus cleaning the dizzy helped for sure.

Many thanks to all who replied to me.

Cheers
Allen