Race Engine Forum UK

Guy,

on my Fiat 132 series 1592cc engine spark plug no 3 is always white.
Engine layout:
pair weber 40IDF carbs
BS1 cams
Pertronix breakerless ignition
Fuel pump std block mounted

what have I done so far:
changed gaskets head-manifold-carbs, plugs, changed jets on carb no2, changed manifold, changed carb no2.

But - plug no3 stays white or much brighter than the others. Compression seems to be almost equal on all cylinders

Maybe you have an idea?
Regards
Weberhans

Weberhans, hi

if the plug is white after running and the others are pale grey-brown then we have either a plug not firing, detonation in that cylinder or weak mixture.

First go to:

http://guy-croft.com/viewtopic.php?t=468

and buy a Colortune device. I don't think we should guess at causes without using this. This tool fits instead of a regular spark plug and allows you to examine the spark and combustion flame with the engine idling and the operation of the pump jet on throttle opening.

Report back when you have the tool and we'll go from there.

GC

Noticed the engine is running original mechanical fuel pump. This will cause a weak mixture. Change to a tank mounted low pressure electric fuel pump. I would like to see a picture how the fuel lines are connected to the carbs. Not fitting them correctly can cause a weak mixture to one cylinder. Incorrect ignition can also cause a white plug.

Andy.

Hi guy ,please excuse that my answer took so long.your suspect the plug is not firing was right.with the colortune i could see that the plug had some sparks missing.so i changed the distributur cap and the leads and everything went grey-brown
thanks a lot from germany

Weberhans, hi

well done! A nice little tech thread with a happy ending for once!

Thanks for telling us the result.

GC