Poor starting and pinking and cut out

[Timotheus]

 

Hi

Recently started with the above, last time it happened (less severe) was with 97 Ron fuel runs fine on 95

The only new thing was a new fuel additive Wynes substi plomb

Is this relevant? Any other ideas, don't know whether engine converted

Tim wilmslow  uk

 

[Peter Cobbold]

Checked points gap ?

[RogerH]

1 hour ago, Timotheus said:

 

Hi

Recently started with the above, last time it happened (less severe) was with 97 Ron fuel runs fine on 95

The only new thing was a new fuel additive Wynes substi plomb

Is this relevant? Any other ideas, don't know whether engine converted

Tim wilmslow  uk

 

Hi Tim,

you shouldn't need any additive unless you are racing or over doing it.

having said that it shouldn't really affect the starting/running unless you have over done it.

Check the carb dash pots for oil level.

Check the timing, plugs, colour of the plugs

Run the engine in the dark if possible to see if it is arcing anywere

Modern plugs are getting to be an issue - they don't like getting wet - I use Champion L87 and get a good 3000 miles out of them

Oil and plug change at 3K

 

Roger

[RobH]

Have you filled up somewhere with contaminated fuel ? Sounds odd that it happens with 97 but not 95.  

 

 

[ctc77965o]

+1 on ignition problem.  how healthy is the distributor?

[Timotheus]

Dampers needed top up front plugs too rich reat sl lean adjusted nuts under carbs  a turn accordingly

No arcs in the dark

Its raining now so will test in the week

Thanks to all

[John Morrison]

Once ha d agroup member with similar,

found this distributor clamp had been overtightened, was cracked, and letting the distributor revolve.

Sudden timing change points to either, really poor petrol fill-up, or ignition timing change.

John.

[keith1948]

If I change from 95 to 97 RON fuel I can get problems because the timing is set up for 95 fuel (4 degrees before top dead centre). Pinking is ignition too far advanced. Rather than points gap checking with a feeler gauge I use a dwell angle meter (57 degrees from memory) because I find it is easier to set spark gap that way.

If you have Stromberg carbs then check that the rubber diaphragms are not split. Just remove top of carb and look at the rubbers visually. Make sure the needle in the carb lifts and falls back easily using the lifting pin on the side. Clean off any soot from around carb piston by lifting it out after removing top of carb. If you have SU's then ignore this paragraph.

I had hardened valve seats fitted 30 years ago so I don't use lead additives. Various views on whether you need them or not. One of our group regularly drives abroad and never uses additives.

If the fuel is old then that can cause problems.

Balance the carbs and make sure that the connecting lever moves both butterfly valves exactly together. You may need to slacken the connector and adjust the 2nd carb rod so both move in tandem. If the front carb starts to open slightly before the back carb then that could explain partly the difference of one being lean and the other rich.

Keith

Edited May 12, 2021 by keith1948

[Peter Cobbold]

1 hour ago, keith1948 said:

4 degrees before top dead centre

That setting  is only used on USA disys with two capsules.  If they are not working correctly - and that is tricky to find - then static timing for a low comp head will be around 15-18 BTDC.

Odd that 97 RON gives problems when 95 does not

Suggest slowly turning dist with engine running to find best tickover, vac retard disconnected.

Peter

[Jase]

I also have some pinking at low revs or when I am changing down to go up a hill. I use Tesco Momentum and an additive but it is still there, I've tried timing and adjusting to suit but to no avail. I'm going to refurb my Strombergs next but before that I'm going to increase the mixture just incase it is a little lean. My other thought is just to fit a new distributor. I also have newly fitted electronic ignition but the pinking was there before.