Engine would not run.

[Ian Anderson]

Those of you who scan the Javelin forum pages may remember that I have, for the last couple of years, been unable to get my Jupiter to start.(I considered selling it at one point) Most of the replies pointed to flooding problems on the standard 30VM carbs. I removed both carbs and blew out all the jets and passages to no avail. They did appear to be overflowing, but I eventually realised that if you keep trying to start the engine and it does not fire, the rich choked mixture collects on the closed throttle butterfly and seeps out of the throttle spindle. I decided the problem had to be electrical but everthing seemed OK but the spark seemed weak and intermittant. I changed the coil but the spark did not seem noticeably bigger, but the engine started for the first time in two years. I am still not confident with the car , but JOAC members will have seen that I took the car up to the top of the North Yorkshire moors where I live and took some photos in the purple heather, one of which is the front cover thanks to Noel Stokoe. The engine is still not quite right though (I could coast the car home from where I took the photo!)
1) It needs a little choke to run until the engine is quite hot, but I don't know if its the richer mixture it needs or just the revs.
2) It "runs on" when stopped after a journey. (normally retarded ignition?)
3) It splutters on pick-up making double de-clutching too slow.
4) It is difficult to start when "half warm"
Any suggestions gratetfully accepted. I went for a ride in Mike Worker's very late SC this week, and he does not have these problems, though his engine and carbs are the same. The only slight difference is that my air filter tubes are about 4mm larger bore. (I had nothing to copy when I made them) I cannot think that this is very critical but I do have a lot more induction roar than him. The engine sounds rather like big ends knocking when pushed hard, and has been known to spit back through the carbs. on full throttle.
Cheers Ian Anderson

[Keith Clements]

These are common problems and can have a number of reasons. Search for 'carburettor' on JT may help!

The most likely is one of the needle valves in the carb float chambers. These do not close properly and so raise the level of petrol in the chamber making the mixture rich. If you have an electric (not electronic) pump then you may hear an occasional tick with the ignition on but engine not running. You will likely see petrol coming out through the (worn) throttle spindles or, if you look down the carb throat, see petrol on the butterfly or dripping out of the delivery tube.

The next possibility is too high a petrol pressure caused by the wrong pump. A pressure regulator might help.

Another common issue is a pierced float. Rattle it and see if there is anything inside. Also see the level of petrol when you take the chamber off (carefully).

Another is a poor seal in the gasket between the float chamber and the carb body at the top. Or loose float chamber.

Loose or incorrect jets. Over the years the jets may have been changed, modified or may be just the wrong ones for the car.

[Ian Anderson]

Hi Keith
I have been down this route in the past. I am confident that the float chambers are not overflowing. The petrol was only seeping out when the engine was turning on the starter but not firing for a long time (30 secs?). If I left the ignition on but did not turn the engine - no seepage, and the pump only pumped about every 60 secs. All the other things you mentioned I have already checked out. My initial problem would appear to have been a faulty ignition coil and not carburation. As I said the engine now starts OK apart from when it has been stood for half an hour or so from hot. It is now just that I am trying to get the engine to run better with adjustments to mixture and ignition but I am loathe to move things too far as I am not sure how critical or sensitive the adjustments are, especially the mixture.

[ian Howell]

Just a thought . . .

Have you tried a different condenser in the distributor?

I did some experiments a couple of years back - no condenser, duff condenser, good condenser, etc.

The results were startling!

With no condenser there was a very weak spark.

With the duff condenser the results were intermittant.

With a good condenser the spark could be well over 15mm long - I didn't try for more as this raises the voltage to critical levels and could damage the coil.

Worth a try?

[Ian Anderson]

Sorry for the delay in replying, but it appears I am/was having Cookie problems on the new server! When I was trying, without success, to get the engine to start, I did check the new (Holden's) capacitor. I only have a low voltage multimeter, but the new capacitor seemed to have less "kick" than the original 1950's one so I put that one back. At the time, there was a lot of correspondence in the Morris Minor Club about new capacitors failing. I intend to change all the plug leads and plug caps so, if the spark is still weak, I will change the capacitor for another.

[ian Howell]

Any further news? If still a problem, a friend recently had a similar problem with his 50s Vauxhall which turned out to be a cracked/tracking rotor arm.

I suppose similar problems could arise within the distributor cover, the coil end cap or even dodgy plug !eads or caps as you suggest.

I did have a problem MANY years ago on one of my Javelins, when the plug cap became 'cooked' and leaked sparks. I found this the hard (ie painful!) way!

[Keith Clements]

The sparking system needs all its components functioning properly keeping 10000volts going where it should do is difficult. Firstly getting that voltage needs good earths, good delivery of current through the ignition switch, good points and capacitor and that is just the low tension side. A multimeter helps to check for any voltage drops in the circuit. Do make sure the ignition coil is the correct polarity and the correct way around. Do the graphite pencil test.

Then choose a dark night and see if you can see any lightning under the bonnet. I have seen sparks coming out of the leads onto the carb and onto the fan spindle. If you have the shielded covers, they can track. I have a transparent Perspex distributor cap which can also demonstrate some leakage. If it is a damp night your problems will be more apparent.

The wires to the points (plastic insulator) and the corresponding earth wire can also be fickle. Many hours were spent tracking that down on the Spencer Jav.