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Engine cutting out

Good Evening All,

I wonder if I might plumb the depths of the collected knowledge, lore and fable in search of a solution.

The equipment: 1933 RP, high compression head, 1" SU straight to the inlet manifold, Bosch dizzy, new tank of fuel, 12 v electrics, rear tank, mechanical pump, super unleaded, no additives.

The symptoms: Last year I was plagued with an intermittent cutting out when driving. I went through the electrical system and eventually having replaced everything else, replaced the coil which seemed to cure the problem for a few months. In addition it was almost impossible to set the tick over so that the engine would not die when coming to a halt at a junction etc. Every time the engine stops, when checked the carb bowl is full of fuel

I have been spring servicing and preparing for the London to Brighton on Sunday and the symptoms have returned. The idle cannot be set so that the engine does not die on slowing down for a junction and at intervals while driving the engine just dies. If I coast and leave it in top gear, I can usually get it to restart and pull away again with vigour. If I come to a halt it always starts, usually on the second pull of the starter. The cutting out will get progressively more frequent until it is every 500 yds or so, but sometimes goes for 2 to 10 minutes then reverts.

Actions today: I fitted a different coil, known to run well and fitted a condenser from another Bosch dizzy, known to run well. I have cleaned and gaped the points and plugs. The plugs are showing the right colour, no signs of oiling. The leads are new last year and the cap and rotor arm too.

All last year I thought it was electrical, now I am beginning to think it is fuel related. The carb has done about 14,000 miles since a rebuild, rebush etc. It appears to be securely fastened to the manifold and the manifold to the engine, however tonight, when I was adjusting the tickover, I lifted the carb quite forcefully and the engine died. It would not repeat that trick but there seems to be some correlation between heavy manual moving of the carb and manifold and the tickover, it fluctuates when giving the carb a good tug?

Any thoughts, advice or ideas will be gratefully received and if I have missed the b***ding obvious I shall actually be happy to hear it.

In anticipation

Thank you.....Desperate Jack

Location: Oxford Town in the afternoon

Re: Engine cutting out

Have you done a compression test Jack?

Also, if the piston is very worn, I have known them to temporarily stick when braking.

Looking forward to seeing you at Brideswell by the way :)

Re: Engine cutting out

Typical symptoms of a carb air leak. Had exactly the same issue when pulling or pushing the carb on my Trials Chummy last year. Careful fitting of the carb/manifold flange joint solved it entirely.

Steve

Location: North Yorkshire

Re: Engine cutting out

Sounds like and air leak to me. Either the carb or manifold is loose or there's a crack somewhere.

Re: Engine cutting out

Could it be a blocked fuel tank breather?does it still cut out with the cap off?.

Location: by the trent

Re: Engine cutting out

You Mecka-nickle wizards are so full of good advice on how to deal with it and dead right an' all.

This morning I started the car with considerable difficulty, a new departure that, but once started and warm, managed to settle it on tick over. Brake cleaner spray certainly made the engine pick up, sprayed on the ends of the carb spindle, and very slightly on the carb to manifold joint, however, was that as a result of the ether being sucked into the carb intake?

I removed the carb and as predicted the flange was banana shaped. The granite worktop sink cut-out, a piece of sticky backed oxide paper, a few minutes work and the flange was back to flat. Checked the manifold brass nuts and the manifold flange, all well, tightened a few screws on the carb, popped it back on for a test run. At that point the normal run of items which demand attention feeling neglected as they do, have to be attended and kick-in. The choke wire unraveled, the carb spindle tapered brass pin needed fettling to clear the manifold stud nut, then the starter switch began to smoke. A few hours later the car started and after adjusting the mixture and slow running, then the steering column gas control rod, which was now fouling the advance control rod, removing the starter to tighten the through bolts, replace the worn brushes, and on and on.

The test drive was uninterrupted by engine stoppages, at junctions the engine slowed to a tick over without stopping, magnificent, what skills in diagnosis and insight you have. Thanks to all who responded on the web site and by email, I owe to you a night of peaceful sleep to come.

A couple of queries remain buzzing like irritating midges on a scottish beach. Why would the air leak, which was obviously not present at all times, stop the engine and not just produce fluffing and a lack of power for a few seconds before righting itself? If the air leak was so sever as to stop the engine, why would it reseal within seconds when the starter was pulled for the second time? How come the air leak was intermittent, when the flange cannot have been moving between straight and warped? I can understand that the air leak would have made it near impossible to set the tick over, but when running normally at about 40 the engine would suddenly die completely, just as if the ignition switch had been turned off?

Perhaps I shall never know, but that old saying about "When you are sure its electrics its gas and when your are certain its gas its electrics" was playing in the back of my mind all day.

Whatever, we shall be able to attend the ball after all, the handsome prince has spoken and the remedy fits the need!!

Ta very much to all concerned

Location: Oxford Town on a sunny afternoon

Re: Engine cutting out

Well done Jack
Really pleased you have managed to sort it out sorry can't really give you answers as to the why s
Maybe a heat thing different metals expanding at different temperatures or something along those lines
See you at Brighton then
Bob
Surrey

Location: Surrey

Re: Engine cutting out

I found that on my ulster tt rep the carboreter manifold gasket was letting air into the engine as it ran The gasket had a small chip taken out of it because the bolts holding the carb manifold to the engine were loes and the entire jig warbled it's self to death.

Location: Somerset

Re: Engine cutting out

To update the last posting, we left Stonesfield, north of Oxford, on Saturday afternoon and spent the night in Putney with friends. On Sunday morning we joined the event and got to Brighton at 14.00. We left at 16.00 and arrived home at 21.00.
The round trip was 290 miles and the engine ran faultlessly. The last part Brighton to Stonesfield was through Pulborough, Petersfield, Basingstoke, Aldermarston, Tadley, Streatley, Oxford and home along some really nice roads, the late spring evening sunshine and the early blossom and brilliant green of the first blush on the trees made it a picture, 123 miles in 5 hours less a fuel and comfort stop and one to help a chummy in distress.

Thanks to all concerned on the fix and those on the journey.

Result!!!

Location: Oxford Town on a sunny morning

Re: Engine cutting out

Excellent news Jack, by the time I was ready to reply, half the forum had diagnosed the fault and posted replies, which just goes to show how much knowledge is available through the Friends web site!

Location: Near Bicester.