Reluctance Of Engine To Start

[Mike Allfrey]

Hello Chris,

When you mention the choke system, I assume that you are referring to the carburettor strangler systems on Javelins and Jupiters?

I have seen a number of carburettor bodies with excessively worn bores for the strangler blade shafts. Also seen are worn shafts where they pivot in the bodies. This wear allows air leakage during cold starts, that upsets the petrol/air mixture required for cold starting. In addition to that type of concern, should the strangler rods and cable be set too tight, rocking motion of the engine will accelerate wear at the strangler shafts.

In the days when I was living in Derbyshire and using my Jupiter as the 'daily runner', I was convinced that everything truly had to be right for a quick cold (winter morning) start. That was in the days of leaded petrol as well, and staying well away from the dreaded Jet brand.

Down here in Melbourne, cold starts are never as cold as they were in Derbyshire and, while we had leaded petrol here, our cold starting was always quick and the engine soon settled down to the easy beat that we know. Australia used to refine its own petrol and, with the introduction of unleaded petrol even our mild cold starts started to become a bit difficult. Now all of our petrol is imported and cold starts are more of a challenge. This has become more so since our State Governments have brought in differing petrol specifications for petrol, while pandering to environmentalists.

With these petrols, the volatile components in the petrol do boil off easily. Hence the petrol smell in my garage when the Jupiter and the Rover cool down after a lengthy run. Now that the petrol pumps are wired through an on/off switch and the engine is run out of petrol prior to switching off the ignition, cold starts have (once the pumps have filled the float chambers) become very much quicker, and the engine quickly settles to its even beat.

I agree, the strangler/choke system does need to be correctly adjusted,

Cheers,

Mike A.

[Mike Allfrey]

Hello Folk,

An update on this subject. Malcolm from BP has made two presentations at our AOMC Delegates' Meetings (these are similar, I suppose, to the FBHVC in Britain), he has also come to a Rover Car Club meeting and the question time featured carburettor float buoyancy in fuel that has suffered boil off of combustible components and how it relates to the fuel level in the carburettor. The reply was that, in depleted petrol, a float would sit lower in its bowl and, in some cases could cause flooding symptoms. This has indeed happened on a couple of Jowetts here, and it is usually the L.H. side carburettor that shows signs of flooding.

When at college we had hammered into us the importance of having the correct carburettor petrol level. For me, this was particularly so with TVO fueled tractor engines and was probably worse with those engines set up for use with lamp oil (Spain). The aluminium washer for the needle and seat in the Zeniths is a specified thickness to ensure a correct petrol level at all times. Too often, carburettor float bowls have been removed and extra washers have been found fitted between the seat and the carburettor body - probably installed to fix flooding symptoms - but mostly altering the petrol level.

We were taught that the modern (1956) carburettor performs an extremely critical balancing act - air intake into the choke and the petrol delivery into the air-stream in precise proportions. That is very true!

Keep safe from the Plague wherever you are,

Mike Allfrey.

[AmilcarJohn]

Recently I tried to start my Jupiter which hadn't been run for some time. It turned over fine but wouldn't start. I assumed the fuel had gone off (volatiles evaporated), since it is at least 7 months old. However, after tightening the earth strap from the battery, and another which I previously added from the starter motor to the chassis, it started first press. I do wonder whether the quality and shelf life of fuels is as bad as we sometimes assume.

John

[Mike Allfrey]

Hello John,

The lack of an earth strap from starter flange bolt to sound earth at chassis, sort of amazes me. Maybe the choke or throttle cables were glowing while cranking? A good earth here is vital for the ignition system as well. With the DKY Lucas distributor it can be helpful to add an earth wire from the distributor body to a convenient engine bolt.

I do not know about the quality of petrol in foreign parts, but here in Australia it is not very good, seven months shelf storage here would cause difficult starting.

I could well be totally wrong, however, since being able to switch off the SU pump and letting the engine run out of petrol, engine starting is much easier and the cessation of petrol fumes in my garage after a lengthy run is a good thing.

Regards,

Mike A.

[Mike Allfrey]

My Jupiter was last used in late February, 2020 and has spent the COVID-19 lock-down in my garage with the C-Tec trickle charger doing its job. This morning, after a chilly low over night temperature of just 8 Centigrade, and the garage at 9 degrees, I decided to give the engine a run for a spell. The petrol pump was switched on and given time to pump petrol into the carburettor float bowls.

With choke (strangler) control fully applied, the engine coughed at the second stab of the starter button. The choke was released a small amount and the engine fired immediately to an even beat fast idle. It was held at 1,100 R.P.M. for a few minutes and then allowed to low-idle until some warm-up had been achieved - warm air exiting the bonnet louvres. The steam at the exhaust ceased quickly and the engine was given several throttle blips to 3,000 R.P.M. to blow out the cobwebs etc.

The petrol pump was then switched off and the engine allowed to physically run out of petrol, the ignition then being switched off.

The petrol's age? Just over one year.

I think a point has been proved.

Keep well,

Mike A.

[AmilcarJohn]

Very good to hear that Mike - especially as draining a petrol tank, and finding a way to dispose of the petrol is one of the most unpleasant old car jobs. I still remember the smell of 1960's petrol left in the tank of a Javelin I restored in the late 1980's. Yuk.

[Mike Allfrey]

Thanks John,

Digressing a bit, while working on a farm tractor, probably about 1960 and up on the Mendip Hills, there was a Blue Streak Riley Kestrel in the back corner of the large stone walled barn. I was told it had been in storage since the start of WW II (1939) and the farmer had never done anything with it. Out of interest, we connected a new battery I had in the van, old petrol was pumped up and the engine started quickly. I was told that the tank had been filled with Cleveland Discol just before storage.

The owner flatly refused to sell that beautiful and very original Riley. Otherwise, I could have been involved with high camshaft engines!

Regards,

Mike A.