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Smooth running then lumpy and cuts out


vitesse driver

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Been having this problem with our Mk 2 Vitesse. It starts fine and ticks over nicely but when driven it starts to get lumpy on acceleration and then shortly after it dies completely. New carbs have been fitted along with points, plugs, leads, distributor cap, rotor arm and condenser.

I have noticed an air bubble in the fuel line just before the fuel pump and wonder if this is the likely cause? When I manually pump it the bubble stretches but does not enter the pump so stays in place. 

Any advice gratefully received. 

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Is the air bubble in a fuel filter? Do you mean the filter appears only partially full? If so that's not a problem, they all do that.  But more air when you pump could be an indicator that there's a blockage further back in the fuel line or tank. Or the tank is not venting and you're getting a vacuum build up. When it dies while you're on a run jump out and open the fuel filler cap, is there a woosh of air into the tank?

Doug

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Air in the filter is not a problem depends on the angle if trapped it stays in there 

One place to check is the small hose from the top of the tank reserve suction pipe to the supply tube this gets missed as they go

Hard and it sucks air but doesnt leak fuel  much.  And the pump can't supply enough fuel to maintain running

There are some awful condensers on sale ,  

And then theres the dreaded rubber slivers  when you fit hoses the metal pipe slices a small sliver off which floats about and blocks the back of the  carb  float needle valve when fuel, is on demand

As you have fitted refurb carbs this is highly likely

Pete

 

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I have now had two "episode's" with NGK plugs.  Fine when cold, but once hot start to fail. They were purchased from the club shop. I'm no longer going to buy them. Not saying this is your cause, but just a note in case you find nothing wrong on the fuel side.

Aidan 

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8 minutes ago, AidanT said:

I have now had two "episode's" with NGK plugs.  Fine when cold, but once hot start to fail. They were purchased from the club shop. I'm no longer going to buy them. Not saying this is your cause, but just a note in case you find nothing wrong on the fuel side.

Aidan 

Hi Aidan , what plugs are you replacing the NGKs with 

Paul

 

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On 9/2/2018 at 9:50 AM, dougbgt6 said:

Is the air bubble in a fuel filter? Do you mean the filter appears only partially full? If so that's not a problem, they all do that.  But more air when you pump could be an indicator that there's a blockage further back in the fuel line or tank. Or the tank is not venting and you're getting a vacuum build up. When it dies while you're on a run jump out and open the fuel filler cap, is there a woosh of air into the tank?

Doug

Where does the fuel tank vent from? All I can see is the fuel line coming out?

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Ok , do a physical check pull push and tighen the hose clip,  this leaking air has stopped many a car .when fuel, is on demand

Next is strip the float needle  look behind it,   , flush out the feed pipe into a jam jar with a few squirts

See if you find any small rubber slivers

Whip the top off the pump  is it clean inside ?

Pete

 

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