Intermittent Sparking at the Spark Plug

[nam]

I am trying to get my engine started and have got close now. I have so far replaced the following:

Distributor Cap
Rotor Arm for a Red One
Points and Condensor
HT Leads
edit: also New Spark Plugs (NGK)

I am getting a spark across the points when i flick points or engine turns over. Get a spark at the king lead, checked HT leads firing order 1,3,4,2.

Now when I am turning over the engine it takes maybe 5 or 6 turns of the engine to produce a spark on plug 1.

What mostly confuses me is why I am getting a spark that only comes sometimes. Any ideas before I strip down the distributor and start putting it back after checks, thanks. Also does my vacuum advance need to be 100% right, as someone has bodged it a bit when it leaves the carb with a bit of rubber hose to connect it.

Engine is a 1098cc and distributor is a 25D top entry.

[mogbob]

A "duff spark plug on number 1 cylinder ? Are you getting a good spark on the other three ?
Try swopping one of the other "good " spark plugs to number 1, if you get a spark..problem solved.

Are both threads on No 1 clean, so that there is good contact ? i.e the plug thread and the thread in the cylinder head.
Bob

[nam]

Knew I forgot something, All the spark plugs are new and clean. I will check the others and see if they have a good spark or not. I also checked the plug gap with a feeler gauge and it is good.

[bmcecosse]

Why another thread on the same problem?? The vac advance doesn't matter a hoot at the moment - but it MUST spark at every second turn of the engine.... I'm sure it's been asked before - is there a good spark at the king lead EVERY time you flick the points ??

[MarkyB]

Does the rotor arm have a rivet holding it together?

[nam]

Sorry for the new thread. I thought it was a new problem and better in the electrical section. Anyway I found it wasn't flicking at king lead everytime. So I took lead off the coil end. Pushed it in further first from the metal bit. Then rubber over. Spark everytime now on flick. And spark at plug 1.

[bmcecosse]

Excellent! You've solved it now !!

[nam]

Yes indeed. Maybe one day I may get this engine started. I believe the sparking is sorted. However one question I have is although I have found tdc at cylinder 1. When I look at the ignition timing marks on the bottom of the engine in relation to the notch in the pulley. Is it important that they must line up as they don't? This is not the original engine in the car so whoever fitted it didn't do somethings right.

[IslipMinor]

What does not line up? Do you mean the dimples on the timing chain wheels? These must be correctly aligned or else the cam timing will be way out.

How have you found No. 1 TDC? Unless something is very wrong, it is found by lining up the long pointer on the timing cover with the notch in the crankshaft pulley, then check that both valves on No. 1 cylinder are closed. If one is open then rotate the engine 180° and check both are closed. You are now ready to set the ignition timing.

To set the ignition timing itself, the notch in the timing pulley must be in between the the first small tooth (5° BTDC) and the end long tooth (0° BTDC) - this will give ~2-3° BTDC static timing. If it was at TDC, rotate the engine anticlockwise 10-20° and then carefully rotate clockwise until the notch is between the long pointer and the first short one. Once that is done, set the distributor with the vacuum unit at the top, and rotate the distributor body anti-clockwise until the points just open (with the ignition turned on you will see/hear a spark). If you need to go too far round bring the body back more than 90° and start again. Once done, lock the distributor in this position and fit the rotor arm. Then fit the No. 1 spark plug lead in the cap so that it is in the position that meets the end of the rotor arm. From there put the leads in the order 1342 in an anticlockwise direction from No. 1.

This will give you a good enough timing set up to get the engine started. If the vacuum is not connected do plug the end of the tube or at the carburettor end.

[nam]

Hi,

What do you mean when you say rotate the engine?

Well BMC has given me loads of good advice and talked me through it and I'm much closer. It's so long and hard to try and explain so I did a little drawing.

I took off the rocker cover and turned the engine with the hande until both valves on cylinder 1 were flat and straight. At the same time I took a spark plug out from cylinder 1 and checked that the compression was building and pushing against my thumb. When I got compression I looked at the distributor rotor arm and then loosened the distributor clamp till it showed number 1 lead in line with the rotor arm.

But on the engine pulley you can see that the notch is nowhere near the ignition timing marks.[frame][/frame]

[bmcecosse]

Rotate==turn. The notch must be close to the timing marks -don't worry too much about getting it exactly right at the moment - however your (excellent!) drawing shows it too far away. I'm not sure about 'valves flat and straight' - I assume you mean 'not pushed down' - indeed you should be able to feel the slight valve gap on each valve when the piston is exactly at the top of the stroke. Simple test - put a drinking straw - or perhaps a chop stick - down the plug hole - now turn the engine and it will bob up and down - when it's at the top, and the two valves are 'flat etc' - then that is the moment when the spark should fire - and the notch WILL be very near the timing mark. Turn the dizzy till the points just open, and clamp it there - and put the rotor arm etc as Richard describes - and I am confident Bob will be your Uncle.......

[nam]

Ok I will try again. But I know I tried the same before and could not get the timing marks to line up at the same time as the two valves on cylinder 1 being flat.

[lambrettalad]

what counts is the dynamic timing ,when your car is running well ,what do the timing marks show 5 degrees BTDC ,3 Degrees BTDC every engine is slightly different

[IslipMinor]

Don't worry about the No. 1 valves being flat, that does not give the precise position of TDC. Line up the notch on the crankshaft pulley as previously described and follow through the instructions. If you have fuel and the rest of the engine is OK, it will start!

[nam]

Don't worry about the No. 1 valves being flat, that does not give the precise position of TDC. Line up the notch on the crankshaft pulley as previously described and follow through the instructions. If you have fuel and the rest of the engine is OK, it will start!

Ok so that I have got it straight:

1, Line up the notch on pulley with the timing marks
2, On the distributor see where the rotor arm is pointing and about to spark, put the number 1 lead on there
3, Choke out and give it a go

Should I be worrying about if the compression has not been felt on cylinder 1 during this point?

[IslipMinor]

Yes, you should as the TDC will be for both No.1 and No. 4 cylinders, but they fire 180° apart. You need to get it 'on compression' for No. 1 - the thumb test or checking the valves will give you right one. Good luck!

[nam]

Right here is my findings.

I took out spark 1 and then started turning engine and found eveytime my pencil was at the top or compression out the notch on the pulley was at the top. Total opposite of the markings. So I took all sparks out and found 4 was also the same. Then I tried 2 and 3 and found that these two are the ones at compression when the pulley notch lines up with the timing mark... Now confused.

I suspect foul play

[bmcecosse]

Don't worry - forget the mark which is obviously wrong - go with the pencil! In #1 hole.

[IslipMinor]

Now confused

I'm not surprised - can only think that the crankshaft pulley may have been changed for something else? Just to confirm the timing marks are at the bottom of the timing cover, underneath the car?

If you can get No.1 at TDC with the pencil, that should be close enough to get it started and the finer adjustments can be done once it is running.

[MarkyB]

Just ignore the timing mark you have, the bottom pulley has probably been change for one off another A series engine that had the timing pointers in a more convenient position.

Putting a blob of Tippex on the mark and the case at TDC will give you a rough guide and save messing around with straws or chop sticks.