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JJC

Running badly - any ideas?

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put the engine back together and it ran fine. Set timing mixture and balanced carbs all seemed right. But now it won’t run unless the choke is right out, pushing it in causes backfiring at both ends. Yes both ends. There also seems to be an intermittent ignition fault so there may be a few things going on. We have checked all the usual stuff so can anyone suggest what it might be? Obviously something has gone wrong since first flashing it up . JJC

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Bad air leak on the inlet manifold bleeding air in.

Mick Richards

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If you have a vacuum pipe to the distributor, check it is ok. I had a problem with the early copper pipe breaking which caused similar symptoms (and it's a bad air leak!).

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Running weak, either air leak (as above) or problem with fuel delivery

Bob.

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Looks like it was vacuum advance pipe in an unsatisfactory (new) rubber fitting under the manifold. But I don’t know because the wretched thing won’t start now. No spark at all. But at least with no spark at all I should find the fault, no chance when it was intermittent. JJC

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On 1/16/2019 at 1:34 AM, ctc77965o said:

Condenser

I once spent literally months and hundreds of pounds trying to fix a ‘fuel problem’ on a marine v8, turned out to be the condenser!

they can cause intermittent and terminal faults, then recover overnight, little ba$tards !

steve

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Yes I’m beginning to wonder but I’ve tried two from MJ (aka DD) which I had lurking around and I would have thought they would have been ok. Can’t think anything could be destroying them? Gremlins? JJC

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If you’ve tried two DD condensers then i’d move on to the next item.

condensers are teicky , but not that teicky!

steve

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1 hour ago, JJC said:

Yes I’m beginning to wonder but I’ve tried two from MJ (aka DD) which I had lurking around and I would have thought they would have been ok. Can’t think anything could be destroying them? Gremlins? JJC

The coils seem perceptible to breaking down, and the modern ones are mostly rubbish. I’ve had two in about 3000 miles. I’d try a Lucas Sport coil or similar quality. Sounds like mixture but may we’ll be electrical.

Kevin

Edited by boxofbits

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Here’s the latest. Not the capacitor, because sparks are now there. I’m told by the experts that if there’s spark and petrol it’ll fire. Well there’s both and it doesn’t. I have tried another coil in case it was weak but no luck. Strangely flipping the contacts by hand gives big spark but turning over with starter and the spark seems weaker. No, it’s not the battery, tried a separate battery for the ignition. 

On the other hand what else is there to do in January?

JJC

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Remove the air cleaners, put some petrol in a squirty bottle, spin it over and give it a squirt direct into each carb, it should try to start.

When it does it proves you've got an air leak, not a namby pamby "oh look a bad fitting on a pipe" but when you strip the carbs off and take the manifolds off you'll find the inlet manifold is fouling the exhaust manifold flange and not pulling down properly giving a mahoolah of an air leak which needs full choke to give some sort of a burnable mixture...try it.

Mick Richards 

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Mick ah yes, that’s pretty much what my expert friend said about the air leak. But! We’ve done the petrol in the carb intake trick and it still won’t fire. It has tried to fire at completely weird moments but not with any serious intent if you know what I mean. More of a cough than a fire. Beginning to think this is a real mystery. Don’t forget it ran fine after putting the engine back together, then all of sudden it doesn’t. Almost certainly more than one fault. Such is life (with TRs). JJC

PS still reading about bump steer

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And another straw clutched at. Thought maybe the coil was causing trouble so tried with a known working coil. Still doesn’t work. 

Think earthing is sound.

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Hi JJC,

        just to go over it all again.

have you got 12V at the coil with ignition on and when cranking.

have you got a spark at the plugs or from the dizzy cap centre wire.

If not - is the LT flexible wire on the contact breakers in very good condition - remove and pull at the tags - the soldering can come adrift.

Try a replacement dizzy (from a running car if possible)

Roger

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1 hour ago, RogerH said:

Hi JJC,

        just to go over it all again.

have you got 12V at the coil with ignition on and when cranking. 

Yes and the battery is new and big!

have you got a spark at the plugs or from the dizzy cap centre wire.

yes, expert friend checked holding the rotor arm by hand and flicking contacts open. Also did usual test with plugs on rocker cover

If not - is the LT flexible wire on the contact breakers in very good condition - remove and pull at the tags - the soldering can come adrift.

Try a replacement dizzy (from a running car if possible)

Hmm, could but I’d probably wind up with two dead TRs.

 

Roger

 

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1 hour ago, stillp said:

Are the plugs wet after trying to start? Are the carb pistons lifting at all?

Well, yes but not very which is a bit surprising. 

Yes pistons lift, jump up and down when turning starter.

Also it didn’t fire when we poured petrol in the carb air intakes. 

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3 hours ago, RogerH said:

Hi JJC,

     I take it that you have oil in the carb dampers

Oh yes I go back a long way. Haven’t looked at diaphragms though. Another straw?

Roger

 

3 hours ago, stillp said:

Strombergs or SUs?

Weepers aka Strombergs

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Good idea to check the diaphragms. Are the float levels reasonably good? Are the float chambers filling?

Pete

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