Misfire

[pistnbroke]

My car has developed a cronic misfire the car is undrivable. Its not long since I rebuilt the engine and fitted new plugs points condenser cap leads so I dont think its electrical. Points and plug gap checked Plug colour seems ok any clues where to start looking.

[bmcecosse]

Would have to say - head gasket may be blown................ You could try a simple compression test using the starting handle with ignition off. Turn the engine over - you should feel 4 even pulls on the handle - if only two good pulls and two easy ones that would suggest a blow between cylinders which is the most usual place. Of course - a proper compression test with a gauge if you have one is better still!

[Kevin]

As Roy has suggested a compression test would be good, other clues could be oil in the rad or water on the dipstick, did the problem start suddenly or has it got worse over time.

[billlobban]

Dont automatically think that if youve replaced it it works. Other than the above have a good look at the ignition system. Are the points pitted or burnt? are you getting a reliable spark? If you have the old stuff you took off if you didnt have a misfire before the rebuild replace the components one at a time (condenser, points etc).
If you need a compression gauge I'll be home this weekend if you want to borrow one.

[MarkyB]

When did the misfire start?
If it was straight after fitting the new bits, you have the firing order wrong, i.e. the plug leads didn't all go on the right plugs.

[pistnbroke]

I tried a rudimentary compression test with my thumb over the plug hole as I dont have a compression gauge. Then I swapped the cap, leads, points and condenser for the old ones. Misfire gone

[linearaudio]

It would be interesting to refit the "new" bits ONE AT A TIME to locate the breakdown. There has been much said in recent times about new rotor arms, so that would be my first check!

[billlobban]

Yes the theory is only change things one at a time then you know what was faulty. What do the points look like now that youve got them off

[MarkyB]

Result!

[bmcecosse]

Thank goodness it's not the gasket! As others have suggested - now refit the parts one by one to find the culprit.

[pistnbroke]

Looked at the points they looked very burnt but as Ive never owned a car with points before then I dont know what to compare them with. I refitted them and their was still no misfire. Then I refitted my new condenser BANG CRASH WALLOP straight away. Brand new just out of the box has only done about 50 miles. Its now in the bin.
Where should I buy reliable electrical parts

[bmcecosse]

The burned points told me it would be the condenser....... it's there to protect the points - and to boost the voltage from the coil. The famous 'new-old-stock' seems to be the way. Was yours a genuine 'Lucas' condenser ?