tr3a Running On

[Richardtr3a]

My 3A is starting every time now, like a modern car. My new 88amp/h battery has really helped. I have now put the charger back on the shelf.

 

However I am getting less than 30 mpg and would like to do better as I have a 350 mile drive at the weekend and then back as well. The plugs look brown at the point but there is some black deposit on the insulator. I am using SM needles.

 

Last night when it was hot the engine ran on twice when I switched off. Can you remind me why this happens? I tried a search on the forum and got no results.

 

thanks

Richard & H.

[Peter Cobbold]

Richard,

It can be a symptom of over-retarded spark. Check points gap and spark timing.

If the poor mpg has happened rather suddenly then wear on the plastic points cam follower is a prime suspect - they work better with a smidgeon of grease,

The sooted plugs and poor mpg suggest its not running too lean ( which can aslo cause running-on).

Peter

[Richardtr3a]

Thanks very much.

 

I need a proper tuner near me in Lewes Sussex. Can any one recommend a workshop please?

 

I have used Southern Carburetors but they have gone from South London and I need someone closer and with a rolling road preferably

[BrianC]

Setting your car up on a rolling road won't necessarily improve your fuel consumption - at least not if you expect more than 30mpg.

It may (or may not) improve performance if that's what you want and (as in my case) show up other faults. Not cheap, but well worth the money if you know exactly what you want out of the exercise and can find the right man for the job. Somehow, unless your engine and exhaust sytem are modified, I suspect your needs are rather more basic and probably only require simple carb and timing tweaks. Otherwise, you will have to drive far further than 700 miles to recover the costs of a decent diagnostician from fuel savings.

[vivdownunder]

Might need new carby needles and jets. It's hardly visible, but the jets can wear slightly oval, thus causing a stronger mixture and running on. Needles and jets should be replaced as sets.

 

If it still runs on after being looked at, sit at tickover for 30 seconds, turn the key and at the same time flatten the accelerator. The ingoing rush of cool air usually quenches any hot spot.

 

On the highway an O/D car with engine in good shape, correctly inflated tyres and not driven like it was stolen, should top 32mpg. Non O/D something like 28mpg.

 

Viv

[Grahamgl]

Richard,

Using supermarket fuel my 4A tends to run on, in spite of having fitted two anti run on valves and using Castrol Valvemaster plus. However, when I put Shell petrol in the tank no run on at all. Decided that I am going to stick to premium branded petrol in future. Folklore also says that the petrol consumption is better using premium branded fuel. Never checked mine however.

Graham

[JeffR]

It's also possible for run on to be caused by a hotspot in one of the cylinders, for example if any of the waterways are silted up in the block. A simple check is to remove the coolant drain plug from the rear right hand side of the block and see if water emerges.

 

Do this with the engine off and the radiator cap removed.

 

If no water runs out you probably have a silted block which could be adding to your run on woes.

 

Best of luck,

 

JEFF

[RogerH]

Hi Graham,

if the poorer quality fuel is possibly causing your problem then you may have another problem!!

oil blowing by the pistons has the net effect of lowering the RON of your fuel and causing similar effects.

 

Are your pistons slapping about like a pork sword in an alleyway!!

 

Roger

[Fireman049]

When I stripped down the engine of my 3A the block was thick with crud and rust.

The hole for the drain tap is very small and rough cast and packed with crud.

I used a Dremel with a parallel burr to really open up the drain hole.

I also coated the block walls with anti corrosion paint.

Unprotected rough casting is a haven for the build up of rust and sludge.

 

Tom.

[Grahamgl]

Hi Roger,

No oil on the plugs. Pork sword not slapping at all!

 

On another subject, the car used to always have a slight emulsion deposit on the oil filler cap and in the PCV. I washed the filler cap in petrol, this removed a fair amount of black crud from it and also cleaned the PCV. Let the cap dry out over night and replaced it and the emulsion problem has gone.

Graham

[boxofbits]

Hi Richard

 

It might be your idle speed is too high? Needs to be around 800/900 rpm, but timing and mixture needs to be checked first, and I would second Graham's comment on fuel quality. As far as I know, only BP and Shell put the correct additives in fuel. I use BP without any issue.

 

Try Caburn Classics in Ringmer and ask to speak to Jeff. He'll be able to sort an engine tune for you.

 

Regards

 

Kevin