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No spark - completely stumped!


Alastair_Smith

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Can anyone help please?

 

I have a GT6 MK1 that I rebuilt a few years ago. In the past it's run well but in the last three years I've refurbed the carbs (Stombergs), had the head converted for unleaded and moved house so I havent been running it.  I just tried to get it going and it won't start.   The obvious problem is no spark at the plugs. 

I know the low tension side of things is fine and the coil because I can get a spark with a plus inserted into the main lead from the coil and held against the engine block. But when I connect the main lead back to the distributor I don't get a spark on any of the plugs.

I have changed the points, capacitor, rotor arm and distributor cap but no change.

I know that there is connectivity between the distributor cap main lead socket and the brass rotor arm - ie the spring on top of the rotor arm is making it's connection with the cap. 

Interestingly the leads (which are almost new) have a 2kOhms resistance - I would have thought they would be conductors but they are all the same so I assume they're ok?

For some reason the HT is not getting back out of the distributor via the rotor arm.  I thought that maybe the rotor arm position was way off. Can't think why but I went through the process of re-setting the static timing - 13 degs BTDC with cylinder 1 on it's compression stroke and the points just opening (checked with a 0.002" feeler gauge). The rotor arm is pointing straight at position 1 on the distributor cap. 

I'm completely stumped. It must be something daft that I'm missing but I'd rather be made to look stupid and get it sorted. I don't really know what to look at next. 

Anyone got any ideas please? Thanks.

      

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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...

Those leads are resistive ones to suppress radio interference and although theres a small volt drop along them this wont be the cause of the problem. 

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1 hour ago, Alastair_Smith said:

changed the points

You have got the wires on the right side of the points round insulation (usually red) spool in the end of the spring arm.

In my youth I put them on the wrong side and tried for 30 min to start the car to no avail until the penny dropped

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Peter T: thanks, this is the sort of thing that it must be. Not sure I totally understand your response though. Do you mean the spring arm is insulated from the low tension? I know that isn’t the case because if I turn the engine over with the cap off I can see the spark at the contacts. 
 

Peter L: thanks, it’s a Delco 202. I bought two rotor arms from chic Doig and rimmers so that I could compare two sources and they’re identical. They both came in a Lucas box but chic assured me on the phone it would fit. The one I took off is very sloppy in the distributor shaft. These two new ones aren’t. 
 

Johnny: thanks, I’ll give that a go too and report back. 

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38 minutes ago, Alastair_Smith said:

Peter T: thanks, this is the sort of thing that it must be. Not sure I totally understand your response though. Do you mean the spring arm is insulated from the low tension? I know that isn’t the case because if I turn the engine over with the cap off I can see the spark at the contacts. 
 

 

That answers the question, it was my blonde moment around 1966! Re Delco Dist Cap there is a carbon pickup in the cap centre top for the Delco Rotar spring to contact with? Oh for the Mini days where you could get an aftermarket see through dist cap so you could see what was going on!

Edited by Peter Truman
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I've just received a new Delco cap and rotor from Paddocks, they sent the wrong rotor. I phoned, they sent the right rotor.

So, just to be clear, Delco is on the left, Lucus on the right. Lucus will fit, but it won't work!

image.png.d0e5cfa8b362ab426205d6e2d8313b79.png

Doug

Edited by dougbgt6
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1 hour ago, Peter Truman said:

That answers the question, it was my blonde moment around 1966! Re Delco Dist Cap there is a carbon pickup in the cap centre top for the Delco Rotar spring to contact with? Oh for the Mini days where you could get an aftermarket see through dist cap so you could see what was going on!

Funnily enough I thought I’d found the problem a week ago because I notice that carbon pick-up rattling round the distributor. It had sheared off. A new cap made no difference and I’ve check continuity to the brass of the rotor arm. 

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46 minutes ago, Alastair_Smith said:

Funnily enough I thought I’d found the problem a week ago because I notice that carbon pick-up rattling round the distributor. It had sheared off. A new cap made no difference and I’ve check continuity to the brass of the rotor arm. 

The wrong rotor arm will break that contact off; happened to me (very embarrassingly during filming by the BBC) but if you've now fitted the correct arm that should be cured. If you could borrow or buy a set of the lead testers - those add-ons that fit between the lead and plug and light up when sparked - they may show if there's any spark at all while you move or adjust other components. I use them all the time and have found them very effective.

s-l1600-9.jpg.e220be7cb80930d41c2616d592f73f76.jpg

 

 

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if you are getting a HT spark from the coils King lead then all thats left to loose it is

the cap 

the rotor

the dizzy cam shaft

a small pea bulb linked between coil negative and earth will with ignition on

show a light for each dizzy cam lift of the points check all 4 or 6 do this

red rotors seem to have cured the plague of riveted rotors we all found a while back .

but there fake red ones about 

Pete

 

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3 hours ago, Colin Lindsay said:

If you could borrow or buy a set of the lead testers

I've 3 off those, where they all are now is anybodies guess, but they're chear enough. A friend has a set of 6 and installs them when he goes to car shows. Pulls a crowd when he opens the bonnet and starts up.

Doug

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8 hours ago, dougbgt6 said:

I've just received a new Delco cap and rotor from Paddocks, they sent the wrong rotor. I phoned, they sent the right rotor.

So, just to be clear, Delco is on the left, Lucus on the right. Lucus will fit, but it won't work!

image.png.d0e5cfa8b362ab426205d6e2d8313b79.png

Doug

Doug - Do you have a source for these red delco arms?  Been looking all over and never been able to find them

 

Aidan

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the delco rotor does not seem to ever been affected by rivet earthing 

its the lucas that suffered fakes    and now the red is being faked 

the best bet is distributor doctor for rotors condensers and caps 

Pete

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1 minute ago, Pete Lewis said:

the delco rotor does not seem to ever been affected by rivet earthing 

its the lucas that suffered fakes    and now the red is being faked 

the best bet is distributor doctor for rotors condensers and caps 

Pete

That's my first point of call Pete.

This topic seems very similar to mine !!

Aidan 

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  • 3 weeks later...

Apologies for the radio silence - had to go on holiday with the family. I like to do something active and my wife likes to sit around a pool somewhere hot and do nothing, so we compromised and sat round a pool in Kos for ten days. 🙄

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.

So I've checked the length of the rotor arm from the little pimple which is dead centre, and compared it with the distance of the cap contacts from the centre of the cap.  The vernier calipers in the picture are set to the radius of the cap contacts and there's a good 2mm gap between the rotor arm and the contacts.  Can that be right?  Seems to large a gap to me?

These are both new - the cap and the rotor - so you'd think they would be right.......

Any thoughts please?  Many thanks.

 

IMG_2722.jpg

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