Not Running Quite Right

[myoldjalopy]

Hello.
Advice needed please. My car runs OK but spits and pops a bit when going downhill at certain speeds with the foot off the accelerator. It has also become a bit thirsty on petrol and - unless I am imagining this - the familiar Morris burble is a little harsh sounding. Not quite so much pull going up steep hills either. I had a similar problem before and it was that the timing was slightly out. Friend fixed it. However, this problem returned after fitting new points and plugs. I have checked and re-checked the gaps but to no avail. I have replaced distributer cap, leads, rotor arm as well but no difference. Could it be that when my friend altered the timing the points were not set quite right and, now they are set properly, the timing needs re-adjustment? I would ask my friend to have a look but he is very seriously ill now.

Many thanks for any advice.

Pete

[bmcecosse]

First move - check and reset the valve gaps. Also - put a bit of oil in the carb damper. Then - advance the ignition timing slightly until you hear a little 'pinking' when accelerating up a hill in top gear - and then retard it again slightly until is 'not quite' pinking. You have then optimised it for your engine. And then - do a plug colour check to find out what the mixture is doing. Should be a nice light beige colour after a decent run.

[myoldjalopy]

Many thanks for your reply. Just a couple of questions:

1. What sort of oil would you use in the carb damper? Some people say engine oil, others three-in-one.
2. When advancing/retarding the ignition timing would you use the micrometer adjustment or loosen and turn the distributer?

Thank you for your help.

Pete

[bmcecosse]

Try whatever suits best - I'm for 3 in 1 , but engine oil is fine too.. Try the micro adjust - but it may not have enough movment for any worthwhile adjustment.

[myoldjalopy]

OK thanks, but I wonder if you can specifically address my original question about whether if timing is adjusted when the points are not set quite right and the points subsequently set properly, will the timing needs re-adjustment? I understand altering the points gap does alter the timing.

Pete

[mike.perry]

Set the timing then check the points

[MarkyB]

The other way round surely?

[bmcecosse]

Yes - changing the points gap changes the timing......but the only way to set it is the 'not quite pinking' method......after setting the gap to 12 thou.

[myoldjalopy]

12 thou? I thought it was 15 thou? It is a 948 engine.............

[bmcecosse]

12 thou is fine. More time for the coil to 'charge up' . Actually 2 thou is even better - but all too easily will close up to zero.......

[myoldjalopy]

Well I did all that and still not quite right...............until I noticed two things:

1. distributer slightly loose in the engine - so I tightened up the two bolts
2. exhaust manifold missing one stud, washer and bolt causing slight exhaust leak - so I whipped the missing parts off an old 803cc engine at back of garage and fitted them and tightened the others.

Now engine runs really sweetly but I don't know which of the above two fixed it!

Incidentally, correct carburettor oil can be got from S.U. at: http://sucarb.co.uk/damper-oil/damper-o ... de-20.html

Anyway, all fine now thanks.

Pete

[katy]

Loose distributor wouldn't have helped any.
Timing should always be checked and/or corrected after replacing points.

[bmcecosse]

Don't waste money on the 'correct' oil ..... Oil is oil.......

[myoldjalopy]

A Katy - well, it must have been the manifold leak then!
Thanks,

Pete

[MarkyB]

Exhaust leaking is notorious for making motorbikes backfire, I expect it was that.

[bmcecosse]

And I think it would be the loose dizzy! Not getting a good path to earth........

[MarkyB]

spits and pops a bit when going downhill at certain speeds with the foot off the accelerator

Classic exhaust leak symptom.

Lack of pull up hill and poor petrol consumption -> Loose dizzy.