could it be the dizzy?

[philwaters]

Hi,

 

Went to drive over to Steve Fosters yesterday to check out his aero-screens on my car and cough, splutter BANG - switch off and push the car back up the road (thanks to a neighbour) and into the garage. sad.gif

Phoned Steve up who came over and we spent around 4hrs trying to find the problem - but haven't. Did all we could think off - new plug leads, compression test (fine), valve clearances (were off but didn't fix it), swapped coil with friends old one (who upgraded).... nothing.

But... just as we were going to stop we put the timing strobe on and whilst it looked fine at tickover...when we revved it up just a bit , say 2-2500 you could watch as it missed sparks out... i.e. flash flash flash blank flash flash etc etc ....

I am hoping this is the problem, certainly shouldn't be doing that anyway. Would it mean that you had a cylinder full of unburnt fuel which gets chucked out the exhaust and could ignite and misfire....? I can only think that it must be the distributor, but can't see how it would/could start missing sparks out...and not fail completely.

I have the friends old one to use as a test, but the problem is that he also gave me a little ignition box (box shaped heatsinked thing) which I'm sure I don't have on my car (unless its under the dash and I've never seen it) so not sure it is the same as my one and can be substituted..His car is 94/95 1600 sprint and mine is a 96 Classic - was the spec changed?

 

Does anyone have any good tips on how to swap dizzy's easily or any other possible causes.

 

Help - please.

 

Phil Waters

Q181 ABL - 1600 X/F smile.gif

[Roger King]

 

 

Edited by - roger king on 11 Jun 2001 11:28:47

[Roger King]

On a car of that year, you possibly have the old Lucas ignition system, but with a different ignition box to the finned thing your friend has given you.

 

This system is a disaster from the reliability point of view and it's usually the rotor arm that gives trouble.

 

Have a look at the rotor arm. If it has a plastic rotor with a slotted steel skirt hanging down from it, this is what you've got. Check that the steel skirt hasn't worked loose from the rotor part. This is the usual problem with this kit and it can cause large timing changes. The system is out of production and the only proper cure is to change to a different ignition system.

 

If your rotor arm is not like this, you may have the later ignition system that is more reliable.

 

Missing flashes on a timing light are not that uncommon and may simply indicate that the light is not seeing the signal from the plug lead very well. It is also possible that it does indicate a problem.

[Allan Haighton]

A couple of things which may help

 

My 95 Classic was fitted with an Aldon modified Lucas distributor from new. This has an Aldon 'Ignitor' solid state ignition module which is fitted inside the distributor cap. If your 96 classic is the same, it would explain why you dont have an external electronic ignition box. I never had any trouble with the Aldon set-up.

 

However, I did once have a problem that sounds very similar to yours. Car runs OK on tickover, but when the revs rise to about 2500 there is a continuous misfire - sounds like the car is running on three cylinders only. I went 10 rounds trying to find the cause without success. (Replaced electronic igntion by points, new dizzy cap, swapped around HT leads, plugs etc etc).

 

In desperation I ring up John Noble, who built my engine.

 

Oh yes he says - came across this one a while ago. Take the air filters off and have a look down the carburettor inlets. Has one of the choke tubes rotated in the carb body? This can happen if the choke location screw on the carb body comes loose - the lock screw drops out. The choke rotates under engine vibration - eventually it rotates so much that the petrol from the main jet cannot feed into the choke tube. Hence no mixture into that cylinder when the engine speed is high enough to get the carb on main jets. Hence misfire.

 

Sure enough, one choke had rotated as described above. One lock screw was missing.

 

Solution - rotate choke to correct position. No more misfire. Order two new lock screws and nuts (second set as a spare - I'm not getting caught out by this again). Job done.

 

Hope this helps.

[stevefoster]

We had the filters off and I checked the butterfly opening was ok etc.

Balanced the carbs but did not think to specifically look at the chokes... It was only 3 weeks since we did a full shake down and tightened up ... you guessed it...Phil's loose chokes...

 

Check em out phil....

[stevefoster]

Phil informed me today that a new set of plugs solved the problem at least it runs and revs up ok without missing and the popping / backfiring.

He will do more tests (drive it) tonight.

 

Phil identified it to one plug that was causing the problem!

[philwaters]

Phil himself is keeping quiet as he doesn't want to jinx it into something more expensive!

 

will post tomorrow if this is the cure. unusual for just one plug to go, and if it is this it will only have done 2k miles, although they were quite hard miles on the Haggis Hunt.

 

Phil Waters

Q181 ABL - 1600 X/F smile.gif

[philwaters]

Well having had a very quick drive last night and then another one into work this morning I can say that it must have been the plug as it was running fine again. 'Touch Wood'.

I still can't believe that a plug would go after such a short time - still mustn't grumble as its cheap and easy to fix and I can relax again now.

smile.gif

 

Thanks for replying everyone and let me know if you've heard of similar plug stories, be interesting to know mine wasn't a one off.

 

Phil Waters

Q181 ABL - 1600 X/F smile.gif