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Vapor Lock? advice please


wayne1953

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My Classic VX 1600 with twin Webbers does not like going out when the sun is shining - which is great in the current weather.

After 5 mins in traffic it just cuts out completely, the fan does not kick in so the engine is not running hot.

The fuel pump will run and the engine will turn over (unless i flatten the battery) and It will not start at all for 10 or 15 mins when it suddenly respond to the starter. I have recently replaced the fuel pump as it was making a clatter but it has not made any difference.  i am wondering if i am getting a vapor lock as it only happens when the engine is ticking over in traffic and not when I am blatting about.

The battery is also knackered so that does not help with the restart but would that effect the fuel flow?

Any thoughts much appreciated.

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You say the battery is (knackered) do you think when sitting in traffic the voltage drops to the fuel pump due to the alternator running slow = not enough fuel delivered to the carbs ?.

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Have you checked the carburetors are not over tightened on the Thackery washers,  Over tightening can cause foaming of the fuel in the float chambers that would not be helped by the build-up of temperature under the bonnet when sitting in traffic.

Olly

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What SM25T says as the first step.

You say the battery is (knackered) do you think when sitting in traffic the voltage drops to the fuel pump due to the alternator running slow = not enough fuel delivered to the carbs ?.

Interesting... measure the battery voltage when the fault occurs. Check the voltage and earth at the pump terminals (no need to wait for the fault) and the connections.

But have you decided what battery to fit?

Jonathan

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This brings back memories to my first ever car(Vauxhall Viva), I was seeing a girl in Chelmsford and the traffic was often bad, if it was queued  back further than a certain point I knew I was in trouble, the car would stop and not restart for at least an hour or more, despite numerous AA callouts the problem was never solved. One day I was going to work, I reached the dreadful Canningtown roundabout and sat in traffic, as I finally pulled on to the roundabout it cutout on me and wouldn't start, I lifted the bonnet and for some unknown reason I decided to put a radiator bracket I had in the car between the head and the petrol pipe, problem solved, it never did it again, it was obviously the heat from the engine evaporating the fuel in traffic.  The hours of pain that had caused me!

On another note, when I filled my 7 up for the second time, as I took the cap off there was a big suction of air, does this mean I have a problem with the tank or cap?

Alan 

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... when I filled my 7 up for the second time, as I took the cap off there was a big suction of air, does this mean I have a problem with the tank or cap?

Could do...

Do you have any suspicion of loss of power after a decent run?

I'd go for a run, then take the cap off with the engine running and see if the engine note changes.

Jonathan

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sounds like a blocked filler breather if you get an air inrush when the cap is removed, which will stop the engine, time depending on how much fuel/air is in the tank.  The Facet pumps do click all the time but 'clack' when pulling against a vacuum or lack of fuel. 

Depending on the age of the car and the type of filler cap, the Newton caps need a small hole drilled in them if a breather isn't fitted.  Check the archives for more details and remedies.

Paul

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