Unreliable cold starting

[Ian Anderson]

I have been attempting to wake my SC Jupiter (Zenith Carbs) from it's Winter hibernation. It started first press of the button but ran a bit 'lumpy.' Bearing in mind previous 'old petrol' problems, a couple of days later I drained the old fuel (though it works fine in my lawnmower) and put in new petrol. When I attempted to start the engine, it made no attempt to fire. I removed a plug and earthed it and it sparked OK. I gave up after nearly flattening the battery. A few days later a local mechanic was at my house and I showed him the Jupiter. He was impressed with the look of the car but I said "It's only a pity it won't start." I leaned over, switched on the ignition, pressed the starter and it started immediately and ran smoothly. Now I'm back to square one and it will not fire. I have been advised to change the ignition components one at a time, but will need to buy new ones. I still think it might be fuel/mixture problems, since if it fires immediately its OK and I can push the choke almost home. How do others start their cars? If it does not fire quickly do you reduce the choke to prevent flooding? I am open to any ideas.

Ian Anderson

[Jack]

Hi Ian,

We've had an intermittent similar problem with Amy's SC, and didn't really know why it happened. Mostly it will just kick and fire up no problem, but occasionally it doesn't want to kick and we have similar problems to you.

It will kick with Easy Start, which then seems to get things going, but you don't want to be spraying Easy Start to get it to fire every time.

In a moment of slight desperation at Llandridod, with everyone out for the day and the good old booster pack in another car, and no can of easy start, I tried dripping a small amount of fuel straight into the carb to see if it made a difference. It did. Started first time and ran enthusiastically from there. Obviously don't go nuts with it or it will flood, but approx 10ml in each side got us going and no further problems.

So do not assume an ignition issue. We have not looked into it further, but if you are having this problem a syringe of petrol can be a useful thing to have in the boot. I suspect (with almost no evidence to support the hunch) that there is an issue with the carb getting fuel through, and when warm there is enough vapour and a full bowl helping things along. We will probably leave this one until the winter, as it is intermittent, and when it happens it is easily resolved. We may experiment with fuel pressure before stripping the carb as we have an easily adjustable in line valve.

Jack.

[robert lintott]

It could be a fuel pump problem, are the carburrettor float chambers empty? Bob

[Forumadmin]

Was the choke fully out? And did you pump the accelerator hard twice to squirt petrol in using the accelerator pump on the carb? No need to drip petrol in or Easy Start with a Jup !

Half throttle helps if choke is not out, but ,if it is cold, it should be.

[Jack]

Was the choke fully out? And did you pump the accelerator hard twice to squirt petrol in using the accelerator pump on the carb? No need to drip petrol in or Easy Start with a Jup !

Half throttle helps if choke is not out, but ,if it is cold, it should be.

In our case, the throttle had been pumped, choke pulled, and nearly ran the battery flat with every combination of throttle, choke and swearing before trying the fuel in the carbs, which got it straight away.

Jack.

[Ian Anderson]

Thanks for the replies folks, but I think my problem may be too much rather than too little petrol (mind you, I'm pretty sure there are no accelerator pumps on my carbs) Things have moved on a bit though. I checked the plugs (almost new) and they were sooted up, so I cleaned them and the engine did start - eventually. I ran it at tickover for about five minutes once it would run without choke. I reversed out of the garage to go and get some fresh petrol from the local garage and it stopped and again refused to start. The plugs had sooted up again after just 5 minutes! I cleaned them again and she started again so I chickened out of making the trip for petrol. Things would suggest that the mixture was far too rich but it seems unlikely that both carbs have gone out of adjustment. I was speaking to a Morris Minor expert today and he says he always uses "super plus" petrol and adds lead free additive. I'm still not sure whether "E5" petrol is suitable for vented tanks as it absorbes water from the atmosphere - a problem which is going to get worse when "E10" petrol comes along. I think I might drain the tank again and try petrol from a busier garage.

Cheers
Ian Anderson

[Forumadmin]

MOST LIKELY CAUSE IS A STICKING NEEDLE VALVE OR HOLED FLOAT. DO YOU FEEL PRESSURE AND THE PETROL PUMP STOPS PUMPING WHEN OPERATING IT MANUALLY? OR LOOK DOWN CARB BARREL AND SEE IF PETROL IS DRIPPING.

[robert lintott]

Javelin owners will be familiar with cold starting problems . In my experience it is most often caused by lack of fuel in the carbs ---unless the plugs are dowsed in water !--. I would ingore the sooty plugs for the moment . Also I think Jupiters have Zenith 30VM carbs, as do Javelins, which do not have an accelerator pump so flipping the throttle has no effect. However the Jup has an electric SU pump.

Assuming there is a good level of fuel in the tank, first check is the Pump. With the ignition on is it clicking away and is the filter bowl full?
If not hit the pump with a spanner , not too hard, to see if it starts. If not run a wire direct from the battery,or try another pump. Check through the parts manual for filters in the line which may be blocked.

Another check is , when it refuses to start , remove one or both float chamber bowls on the carbs , are they empty? If so , back to the pump and lines. A temporary substitute is to spray petrol down the air intakes , easy on the Javelin , remove the air filters on the Jup? Indeed check the filters are clean .

The carb float chambers should remain full of fuel after switching off, but with the carbs mounted close to and above the engine evaporation can occur causing the bowls to empty. Also worth checking the screws holding the emulsion block to the bowl are tight , with no leakage. However a good pump should fill the bowls in a few seconds. Unfortunately the Javelin with a mechanical pump relies on a good battery and starter to do this , which can be self defeating --hence the popular electric pump conversion.

Sooty plugs,,hard to comment without seeing them , seems to indicate a rich mixture. Are the choke plates operating correctly and in unison ,are they both fully open when the control knob is pushed in and fully closed when out? Are the air filters clean, try running with them removed, it will do no harm .

Ethanol in fuel should not be the cause at current levels .

Good luck Bob Lintott

[Tony Fearn]

In my experience it is most often caused by lack of fuel in the carbs. Check through the parts manual for filters in the line which may be blocked.

I've just been reading a post on the Sunbeam Rapier Owners Club site. There was a problem with fuel starvation and the chap, who was talking about a boat he had rather than a car, undid the fuel pipe from the tank and the carb, blew it out with air, filled it with carb cleaner as far as he could, left it for a time and then blew it out again with an airline. He had to do it a few times, but was amazed how much crud came out.

Sounds a bit like atheroma in a blood vessel, but easier to remove! However it's something else to think about.

Tony.

[Ian Anderson]

The carbs are 30VMs. They were professionally refurbished about 5 years ago. The electric fuel pump stops pumping when the float chambers are full.

Ian Anderson

[Forumadmin]

DO THE CHOKES fully close ?

[Keith Andrews]

Back to basics.
An engine needs fuel, compression and a spark to fire.
A quick check of an engine that will not fire up, is a bit of ether down the carb....engine start.
If it fires u have spark
If it fires but fails to continue to run u have a fuel issue....be it bad gas, bloked jets/ ports, air leak on suction side of the pump or crap in the lines, fuel pump valves , filters, carb float valves
When cars are stored , sediment gathers in the tanks, then gets pumped thru causing issues, usually intermittent till fixed, new filters etc...this is why I run suction type fuel filters before the fuel pump...and dont forget to service the fuel filter each year

[jowettgeoff]

Of course, there's also that old chestnut - tight tappets. As many on this forum will know, a Jowett's tappet clearances grow as the engine warms. The converse of course is true. If the tappet settings were made on a warm day, it's possible that the valves will not quite close when it turns cold. Even a small amount of lift can make for poor starting. Sounds implausible I know - but trust me. I've been there!
G McA