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Roger Redford

Running on 3...and even 2!

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Good afternoon, all. Long time lurker first time poster here.

I live over in France and bought a French market LHD TR4 (though from the UK)last year and have been enjoying (most of the time...) the ownership and driving experience. Carried out a few changes to it, mainly a modern ally radiator,hoses and thermostat to keep it cool in the warm temperatures down here.

Most of my technical queries have been answered on here by looking back through older posts and questions... thanks chaps! No need to reinvent the wheel, however I have had a recent problem with the running on 3 and to be honest even 2, very lumpy and alarming shaking of the engine, which probably is not doing anything any good, especially the mounts and radiator hoses.

It appears to be on 3 and 4 cylinder which lead me to suspect the carburettor and fuel starvation, given the plugs are firing, good coil, electronic ignition, pulling plug leads 3 and 4 makes no difference to running etc.

Symptoms are worse after it has been sitting a couple of weeks and i think I have narrowed it down to the inlet valve in the float chamber sticking closed, ie. up, in its seat and blocking the entry, as every time I take the bowl off to inspect , it needs a little tickle to release the valve.... so, my question is, has anyone else had this problem, is it a case of wear in the plastic star-shaped valve causing it to stick, and are they available as a serviceable replacement part?

Over to you gents, great site and source of info, by the way.

Edited by Roger Redford

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Welcome to the forum Roger.  Yes the float-chamber valve is readily available in a number of varieties, the differences being in the cone-shaped bit that closes the inlet hole. The most usual one has a rubber 'viton' tip which gives better sealing and yours may already be those. You can buy them from the usual vendors like Moss or Rimmer and also from Burlen who still make SUs and spare parts. 

http://sucarb.co.uk/float-chambers-spares/needle-valve-kits/standard-needle-valves.html

Edited by RobH

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Thanks for that Rob. I haven't got the bowl off at present but from memory it did appear that the tip wasn't rubber, just brass protruding from the plastic outer, so I'll go for the viton tip as replacement in both bowls, and hopefully that'll stop the sticking for a good while.

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I only very occasionaly get those symptoms, when it happens the car usually starts up fine on 4 cylinders, but I get half way down my road, & it reverts to two (3 & 4 being OK in my case). my fix is to stop, open the bonnet, & give the front float chamber a sharp tap (I use the "T" key because it is always handy). This unsticks the stuck valve, & after a second or two its back running on 4. I do have the viton tipped ones, but it happens so rarely it does not bother me.

Bob.

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I had this too.  Usually happened after a while idling in traffic queues, so not much petrol flow going on I suspect and the valve stuck closed.  I recently replaced the valves and no problems since.

 

Dave

====

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Thanks for the replies Bob and Dave. Did you replace them for the viton tips and see an improvement?

I suppose over time the tips wear and the rubber hardens causing them to stick.I have to admit I expected the shaking of the engine running on 2 to have loosened it naturally but as I say, float bowl off and it was stuck closed, requiring some manual persuasion.

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Hi Roger,

you could also use the Grose Jets.  These use a ball rather than a cone to do the sealing.

All the usual suspects do them.

 

Roger

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You say the needles you have are plastic-bodied. I wonder whether those have degraded and are binding rather than the tip itself sticking?  Most of the needles I have used have aluminium bodies.

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If you have a problem with a sticky valve, will the misfire start immediately it sticks or does it take until the float chamber is empty before the misfire starts?

rgds Ian

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Logic says it would start when the fuel level gets low enough to severely weaken the mixture Ian.

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Ian,

It is intermittent, but usually shows after a day without driving as a blip, then clears after a few seconds, maybe the vacuum created inside the bowl from the carb drawing the fuel in it "unsticking" the valve. As I mentioned, after a week or two without use, particularly this summer, it has been there straight away and not cleared, the float bowl fuel probably having evaporated off, is my thought.

 

 

 

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There can be no vacuum inside the float chamber Roger. It is vented to atmosphere by the overflow pipe. If anything 'unsticks' the valve it must be pressure from the fuel pump.

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Bit late replying.   I used the normal nylon-bodied jets - not sure what the tip was made of. I looked into the Grose ball-type,   and there were many reviews that were, to say the least, not good.

 

Dave

==

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