No spark - completely stumped!

[Ian Foster]

Alistair

I have measured a new Delco distributor cap and get 49.8mm between inside face of posts.

My new spare Accuspark red rotor arm, does not have the centre pip on the top, but measuring from the centre of the inner moulding I get 24.15mm.

So by my reckoning, the clearance is 49.8/2-24.15=0.75mm.

Hope this helps.

Ian

[johny]

52 minutes ago, Alastair_Smith said:

There is definitely continuity from the coil output to the brass arm of the rotor with the cap in place (checked with a thin bit of wire poked into the rivet hole of the rotor so the cap could be clipped on for the test).  So it has to be the rotor arm or cap.

'What about testing by remote operation of the coil? Set up the distributor with everything in place and rotor arm definitely pointing to cylinder 1 and a loose spark plug in its lead cap earthed against the block. Then replace the -ve wire of the coil (goes to points) with a temporary wire and with the ignition on you should be able to generate a spark by touching the temporary wire to earth (to charge coil) and then lifting it off. You should of course see a good spark at the plug...'

Did you try this Alastair as it would show if the spark can jump that rotor arm to cap gap you have measured?

[Alastair_Smith]

Thanks everyone - will go back and measure again when I get home.

Will also try the remote operation of the coil asap.

Thanks again.  Will report back.

[Alastair_Smith]

Ok. 

Remote operation did not produce a spark.  So I put the spark plug into the end of the output lead from the coil tried again but also no spark. That should have worked as it bypassed the distributor so am I doing this remote test correctly?  I took off the wire from the coil to the contacts and replaced it with a test lead that I earthed on the battery negative terminal.  I left it on the battery terminal for 1 second then removed it. There was a small spark at the battery terminal as I removed the wire but nothing at the spark plug whether it was in cylinder 1 plug lead or the lead from the top of the coil.  Not sure what I'm doing wrong.

Measurements - my cap is exactly 50mm between opposite terminals and the rotor arm is 23.8 so I have a 1.2mm gap - quite a bit larger than you Ian. 

I guess I need to get the remote operation working with the spark plug in the output lead of the coil then test whether that gap is too large. 

 

[Ian Foster]

24 minutes ago, Alastair_Smith said:

so I have a 1.2mm gap

A bit less than the 2.0mm you were suggesting earlier and I would have thought probably OK.

With your bypass set-up, if you rotate the engine so that the points are closed, then with ignition on, if you further rotate the engine or open the points manually you should be able to get a spark. 

Ian

[johny]

11 minutes ago, Ian Foster said:

With your bypass set-up, if you rotate the engine so that the points are closed, then with ignition on, if you further rotate the engine or open the points manually you should be able to get a spark. 

Ian

Trouble is trying to get it to spark with the dizzy cap in place as then of course theres no access to the points. However cant understand why it doesnt spark even off the king lead as it did before when Alastair tried it🤔Something has changed....

[Alastair_Smith]

Quick update - got it running!  I only identified the problem when I finally changed all the spark plug leads and it turned out that the main lead from the coil had an intermittent fault.  No idea how that can have happened but that fixed the ignition issue and..... it still didn't start. But it was straightforward then to move onto the fuel system and find that both float chamber valves had stuck closed so no fuel was getting through. Cleaned that up and it started. 

Thanks for your help and suggestions.  Really frustrating but got there in the end. ON the bright side I've got several spare rotor arms!

Now just need to get the brakes working better than they are before I dare take it out on the road for the first time since 1977 (I think - the tax disc was still in the car when I bought it to restore). It's been a long restoration but moving house didn't help.

Thanks again.

[Ian Foster]

Well done and thanks for letting us know. Defective king lead, who would have thought it?

Glad you have got it sorted and pleased to have been of help.

Those rotor arms will no doubt come in useful.

Ian