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A simple check of the carbs


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Hi. I have read that members here have taken a look at their carbs to check basic operation without taking them apart or refurbing by taking a cover off to check bowls, floats and needles. Is that right? There is never that much more detail about this procedure so if this is possible would someone elaborate as to the procdure? Many thanks.

Edited by Steve4012
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I would imagine a lot of questions on here can be found on google but I was hoping a forum member with the same type of car as mine might share their experience/ expertise. 

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Look on top of the carbs for the smallest metal cover secured with 2 small screws (The one where the 'fat' air balance pipes attach - just remove these 2 covers and you have access to all the main jets and the idle jets - There is no need to remove the complete top cover unless you want access to the float assembly) .   Remove the jets with a good fitting screwdriver and particularly ensure the idle jets are clear.  I know it breaks all the rules, but I would clear them out with a wire jet  'pricker', as modern fuels leave really nasty varnish thats quite hard to remove with solvents.   For a basic check, apart for checking for leaks or float height, that's about it!   Assuming you have the standard '40' idle jets (its printed on them), I find that my standard datum setting is mixture screws set at 3.5 turns from fully closed.   

If you are planning long term ownership, I would recommend investing in a 4 tube manometer & C02 analyser, then you can do the lot!  

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Steve, that's really helpful thanks. My car has been sitting for 7 years and although most things were replaced prior to storage I would like to check the jets for varnish so will take the covers off and check them hopefully tomorrow. After that I'll be getting the equip you suggested for a more comprehensive check. 

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If its been sitting that long, thats the minimum you'll get away with!   Be mindful of leaks when you turn the ignition on - just to make sure the needle valves (the ones on top of the floats that shut off the fuel are OK).

I'd also drop any old fuel and change the fuel filter that sits under the car near the fuel pump, there's are reasonable chance you will have some accumulated crud in the tanks and the turbo fuel system doesn't like blockages.  

     

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Thanks got most of that covered. It had a c service prior to storage and the timing belts been done again recently. It runs great apart from a hesitation pulling away at low revs so am suspecting a varnish build up so want to check that first.

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Varnish in the slow running jet ...unless you know of the possibility...can be immensely frustrating and annoying. It took me a long time to discover it...and I only did so by trying to measure the inside diameter of the jets...using a piece of guitar string that I had measured with a digital vernier caliper. When the correct sized diameter wouldn't fit into the jet, then I realised what had happened. As Steve910 says, solvents don't touch this stuff...I ended up slowly working the guitar string through the jets, very carefully so as not to go past the varnish and into the brass!! After that, all the hesitancy around 3000 to 3500 rpm went away!! The slow running jets on Dell'Orto DHLA carbs are used all the way from idle, through all the progression phases, until the main jets come online at really high throttle openings. The jets used on the Esprit Turbo are about the smallest diameter that can be got away with on 2.2 litre engines, so any further restriction makes a significant difference.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Also check the pump jets which are under brass screw covers. These are prone to getting blocked as they are very small, and make sure neither of the accelerator pump actuator levers are seized, which can be felt under each carb.

 

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Idle jets checked and seem fine but have blown through with carb cleaner anyway and produce good even flow. One of the idle jet tubes has a tiny hairline crack in though where the jet is pushed into the sleeve. I can't imagine this is significant but any opinions welcome. Onto the pump jets now as per Andyww suggestion.

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My experience of carbs - anything that's even in the slightest not exactly as it should be and you will have problems. great when working a1 hateful things when not

best of luck with it

Only here once

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In fact I think I'll have to replace all four idle jet tubes. Two of the others also have tiny micro cracks appearing from the slotted section that the jet fits into so may as well just replace them all. The first and biggest crack I found, the sleeve is too loose to actually hold the jet in place. It just drops out if I hold it vertically. The pump jets were clear and one of the pump actuator levers was a bit notchy which I've now freed off. I'll stick the idle jets back in with new tubes when they arrive and see if it's any better.

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