3000S - fuel & idle woes
Discussion
I decided to have a go at improving the slightly lumpy idle by adjusting the idle screws, with little improvement so far (a 38 DGAS). One side seems fine - easy to adjust from rich to lean and to hit the sweet-spot. However, on the other side, I cannot seem to get a really rich mixture, just very lean -> lean, so difficult to know where the sweet spot is likely to be.
Anyway, before going further, I decided to check the fuel system itself. I have an Facet electric pump, fitted in the engine bay and the 'usual' feed/return to an ally tank. The filter within the pump is clean. My system also has a separate glass bowl fuel filter at the inlet to the pump and when running, I can see air bubbles in the fuel, similar to once when I was very low on fuel. The bowl is never quite 'full' when running, even when the pump is running but the engine off.
Perhaps not related, but I have also noticed that after filling up, the engine will fade under revs 2 or 3 times soon after leaving the garage ... fuel vapourisation perhaps ... and then settles down.
What is the fuel pick-up arrangement within the tank ? Where could the air be entering ?
And any ideas what I should check within the carb to see why one side does not appear to adjust 'rich' ?
Thanks in advance ...
Anyway, before going further, I decided to check the fuel system itself. I have an Facet electric pump, fitted in the engine bay and the 'usual' feed/return to an ally tank. The filter within the pump is clean. My system also has a separate glass bowl fuel filter at the inlet to the pump and when running, I can see air bubbles in the fuel, similar to once when I was very low on fuel. The bowl is never quite 'full' when running, even when the pump is running but the engine off.
Perhaps not related, but I have also noticed that after filling up, the engine will fade under revs 2 or 3 times soon after leaving the garage ... fuel vapourisation perhaps ... and then settles down.
What is the fuel pick-up arrangement within the tank ? Where could the air be entering ?
And any ideas what I should check within the carb to see why one side does not appear to adjust 'rich' ?
Thanks in advance ...
Hi Duncan
Q1. On the passenger side is there is a vacumn pipe that runs from the pnematic valve to the base of the body, when you remove the pipe (if you have one) is it wet inside?
Q2. With the car running and looking down the throat of the carb can you see fuel drippling onto the butterflies from the accelertor punp jets?
Q3. Remove the pilot jets (brass flat head screw 1/2 way up the sides) and come back with the jet size.
Q4. Have you reset the float valve, 40mm (base of float to face) closed and 52mm open.
Adrian@
Q1. On the passenger side is there is a vacumn pipe that runs from the pnematic valve to the base of the body, when you remove the pipe (if you have one) is it wet inside?
Q2. With the car running and looking down the throat of the carb can you see fuel drippling onto the butterflies from the accelertor punp jets?
Q3. Remove the pilot jets (brass flat head screw 1/2 way up the sides) and come back with the jet size.
Q4. Have you reset the float valve, 40mm (base of float to face) closed and 52mm open.
Adrian@
Tks Adrian .. here are my answers ...
Q1. On the passenger side is there is a vacumn pipe that runs from the pnematic valve to the base of the body, when you remove the pipe (if you have one) is it wet inside?
There is a small pipe from the ? anti-stall assembly ? to the base which seems to be dry. If not this, then I don't appear to have one.
Q2. With the car running and looking down the throat of the carb can you see fuel drippling onto the butterflies from the accelertor punp jets?
Yes
Q3. Remove the pilot jets (brass flat head screw 1/2 way up the sides) and come back with the jet size.
Also known as the idling jets ?? Marked with 45.
Q4. Have you reset the float valve, 40mm (base of float to face) closed and 52mm open.
Yes - seems to be correct.
BTW, do you happen to know the thread on the idling jets holder - seem to have cross threaded one
Q1. On the passenger side is there is a vacumn pipe that runs from the pnematic valve to the base of the body, when you remove the pipe (if you have one) is it wet inside?
There is a small pipe from the ? anti-stall assembly ? to the base which seems to be dry. If not this, then I don't appear to have one.
Q2. With the car running and looking down the throat of the carb can you see fuel drippling onto the butterflies from the accelertor punp jets?
Yes
Q3. Remove the pilot jets (brass flat head screw 1/2 way up the sides) and come back with the jet size.
Also known as the idling jets ?? Marked with 45.
Q4. Have you reset the float valve, 40mm (base of float to face) closed and 52mm open.
Yes - seems to be correct.
BTW, do you happen to know the thread on the idling jets holder - seem to have cross threaded one
Hi Duncan,
MY first thought's are that the float level is not set correctly as the accel jets are drippling fuel, With the cover in the vertical position and float clip in light contact with the pin ball on the needle, the distance from the float base to the upper face of the cover (without gasket) must be 40mm and then when the cover is horizontial, the base of the float to cover should be 52mm, set these using the adjuster lugs.
Do check that the butterflies are closing down at the same time by turning the primary throttle adj screw out and setting the butterflies fully closed using the primary toothed sector (the thoothed gear with the adjusting screw) ensure that these open and close at the same time, then open them an equal amount (.65to .70) and then turn the idle mixture screws out 2 1/4 turns (I would change the idle jets to .50, if you need some say so, and I will drop some in the post, exchange) and do not screw these in too tight as the hole in the jet will close down, nipped up tight and ensure that the 'O' rings are in place. Lastly the main cover gasket and no vacumn leaks on the butterfly side of induction (I have a test for this using carb cleaner but will not put it into print!) has to be in good condition.
Adrian@
I have no idea on the thread sorry.
MY first thought's are that the float level is not set correctly as the accel jets are drippling fuel, With the cover in the vertical position and float clip in light contact with the pin ball on the needle, the distance from the float base to the upper face of the cover (without gasket) must be 40mm and then when the cover is horizontial, the base of the float to cover should be 52mm, set these using the adjuster lugs.
Do check that the butterflies are closing down at the same time by turning the primary throttle adj screw out and setting the butterflies fully closed using the primary toothed sector (the thoothed gear with the adjusting screw) ensure that these open and close at the same time, then open them an equal amount (.65to .70) and then turn the idle mixture screws out 2 1/4 turns (I would change the idle jets to .50, if you need some say so, and I will drop some in the post, exchange) and do not screw these in too tight as the hole in the jet will close down, nipped up tight and ensure that the 'O' rings are in place. Lastly the main cover gasket and no vacumn leaks on the butterfly side of induction (I have a test for this using carb cleaner but will not put it into print!) has to be in good condition.
Adrian@
I have no idea on the thread sorry.
Edited by adrian@ on Wednesday 18th April 23:04
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