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Idling issues


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Hi All, 

Previously i made a post regarding some fuel pump decisions i had to make, i opted for the mechanical pump for reliability and ease of installation, pump went in a treat and there was a noticeable improvement on the first start however now the car is struggling to idle. Not idling at all would be a better way of putting it. this was my first time playing with fuel systems so has anyone got a tip or suggestion as to why this may be happening and how i would go about achieving a solid idle again. I am going to play around with the timing this weekend also as it may be up to that but i figured it wouldnt hurt to gather some other opinions.


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Hi James,

                  Are you advising the car runs great, when on the road, but just won't idle ?

Did you put the spacer back in, between the mechanical pump flange & the block of the engine ?

Did you replace the in-line fuel filter ?

Have you disconnected the inlet pipe at the front of the carby,  & then cranked/turned the engine over, & ensure fuel is coming out ?

If there is plenty of fuel at this point, then the issue will most likely be in the carby.

If there is no fuel delivery, or it is very poor, then the fault will be somewhere between the tank & the carby.

First thing to do is narrow the possibilities down, & determine which part of the system, is at fault.

Common faults are . . . .

fuel line sucking air in, between tank & filter/pump.

Carby inlet fine filter blocked.

Idle circuit in the carby needs cleaning. 

Lets know what you find.

Cheers Banjo

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Set the points and timing first, so that is out of the way. Wind up the idle speed screw until it idles, it might be wandering from 1000 to 2000rpm, and see if altering the idle mixture screw makes a difference.  I've taken the screw right out sometimes and its made no difference..

If you can't get them to synchronise in a good idle, then you're onto Banjo's list.  Start with the idle circuit, which means pulling the carb off (check the fuel line filter as you disconnect the line) and then clean out the idle circuit. There are drillings though the carb body, so use an aerosol can with a tube on the nozzle or a syringe full of petrol. Pull the jets out & hose the crap out of all the passages you can find.

The reason I'd start there is that idle uses very little fuel, so if it won't idle its more likely to be in that particular circuit than a pump problem. If the pump or filters are bad at idle it won't run well under power.  The idle circuit actually has an effect on the power up to 2000rpm when it hands over to the main circuit fully.

There are diagrams around on the web although it might be impossible to find the exact one. This might help-




Haha!  WAIT!! Check the idle shutoff solenoid is working properly!  If there is one on the carb it should click on when you turn the ignition on, and click off when you turn it off.  If its not wired in or broken the car will just never idle.


Edited by altezzaclub
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