Uneven fuel mixture, or ignition issue etc, Vitesse mk1 2litre

[daver clasper]

Hi. Car is running well, though plug colour on cylinders 4,5,6 is uniform and about right. Plugs on 1 and 3 look to be running very weak and no 2 plug is very sooty.

Firstly I.

Fitted spare dizzy cap and HT leads

Swapped plugs around

This made no difference and plug colour was monitored regularly over about the past 500 miles.

Today I.

Checked valve clearance's, all ok.

Used an unlit butane torch around the inlet manifold to head gasket area to see if any air leaking in, no increase in revs.

Thinking maybe to do a compression test, to see if no 2 is low on compression and therefore a poor combustion on that cylinder. Worth trying?

The dizzy shaft has always had about, maybe 5 thou" side play at the top. Could this maybe cause weak ignition just on no 2 cylinder?. Car has been running points for ages. I have a electronic ignition that I can fit, that should eliminate the play in shaft. Worth trying maybe?.

As far as mixture goes, I'm not sure if it is set a bit too rich, as maybe showing on, no 2 cylinder and something else is causing 1 and 3 to appear running weak, or mixture is set too weak, as maybe showing on 1 and 3 and something else causing no 2 to appear to be running rich/ poor combustion?

Any thoughts and advice, much appreciated.

Thanks, Dave   

 

Edited October 26, 2023 by daver clasper

[Clive]

A compression test my help, do wet and dry at WOT, all plugs out. However, a leakdown test can be more revealing if you have a compressor and kit available. 

It could be rings or valve guides letting a bit of oil past. A "workaround" would be to fit a hotter plug to that cylinder to burn the deposits off. 

I doubt it is the timing, though you could fit that electronic ignition. It may help with a better spark for all cylinders.

And yes, you may need to richen the front carb a tad to get 1+3 the correct colour. No 2 is rogue!

[daver clasper]

Thanks Clive. Compression test, best done with engine at operating temp?

Car has been running NGK BP6 ES.  I think the lower the no, the hotter the plug?. Any idea which grade of plug may be a good starting point?

[Clive]

BP5ES is hotter. (NGK work opposite numbers to some other manufacturers)

 

[daver clasper]

21 hours ago, Clive said:

BP5ES is hotter. (NGK work opposite numbers to some other manufacturers)

Thanks Clive. I have some spare 5's, so will try one and rich it up a bit as well

[daver clasper]

On 27/10/2023 at 07:12, Clive said:

It could be rings or valve guides letting a bit of oil past.

Have done a bit more plug colour monitoring at higher speeds, since last post. it appears plug colour of 1,2,3 is a lot more uniform when cruising at higher rpm (my previous monitoring was I think at slower rpm/city driving and also a bit oily looking at times?).

Wondering if the sooty and maybe oily looking no 2 plug at low rpm, is caused by oil, causing some contamination of this plug, resulting in it not burning fuel properly/running rich?

Therefore maybe not a compression issue? ( I will do a comp test when I have an assistant as only have the rubber plug type, and also maybe a leak down, if I can facilitate this?).

The comp tester is an older one and seems ok quality, is this bung type/push down one ok, as long as you appear to get an ok seal?.

Any thoughts great, thanks    

Edited December 18, 2023 by daver clasper

[daver clasper]

Hi. If anyone has any thoughts on my last post above?, these would would be much appreciated.

Thanks, Dave