Fuel Consumption Issue...... - Page 2

222s · Oct 3rd, 2007, 17:32

Quote:

Originally Posted by austingipsy

I think one of your carbs has a sticky plunger, maybe a rough spot on the inner face of the carb or the damper is making it hang up and your carb is drinking vast amounts of petrol because the needle's not sat at the right level......maybe, or perhaps your brakes are binding a bit, has there been a change in performance. If it's sounding a bit rough is it struggling to pick up as you drive away?

Yup, sounds rough when pulling away but then clears - I'll check the movement of the carb pistons when I get home from work.

Only change in performance is related to the rough running of the engine & I'm pretty sure that the brakes aren't binding as I can easily push the car.

Derek UK · Oct 3rd, 2007, 18:49

If a dashpot piston is sticking, don't be tempted to clean it all up with Autosol. Petrol and a cloth only. The piston needs as little clearance as possible for it to work with the vacuum. If this is the problem it might also be the cause of your poor running and pinking a while back.

Clan · Oct 3rd, 2007, 19:13

what is the CO set to have you had it checked ? It is very easy to get it 12% and that will cause your problem , it should be around 2 or 3% CO when warm .( or less if the engine will idle ok )

222s · Oct 4th, 2007, 10:05

I've checked the movement of the damper pistons & they're fine. However the fuel level in the aft float bowl is about 10mm higher than in the forward one. Given the way in which the fuel reaches the carb, I think this might be a major part of the problem.....

Anyhow - turns out that the float needle valve is very worn (pronounced step in its taper) so although sealing properly (so not leaking fuel out of the overflow), it closes when the fuel level is higher so it looks like the 'lost' fuel is overflowing through the main jet & thus through the carb. I swapped the needle valves around & it's now running better (but will of course fit new ones as soon as they arrive). Smells a lot less of petrol now too.

Haven't checked the CO but am setting the mixture by lifting the damper pistons & checking the plugs. The front carb is running nicely so once the rear one is behaving, hopefully both running & fuel consumption will be back to normal!

222s · Oct 8th, 2007, 16:59

Took Friday afternon off work so would have more time to sort out the problems with the car. Still couldn't find any sign of fuel leaks, so turned my attention again to the carbs.

Turns out that the choke on the aft carb unit has become a bit tempermental and was sticking open. Combined with the float jet issue, it looks like this was the cause of the 10mpg fuel consumption.... The choke had been fine when the carbs were adjusted the previous weekend, so must have stuck again since - this time though I greased all the carb linkages / spindles etc so that both chokes move smoothly now.

Reset the mixture mainly on the at one, but the forward one also responded to a slight tweak, just using the lifting the carb pistons method (need to look at the plugs to check but haven't had time) & adjusted the idle screws. Now the engine idles very smoothly (also picks up without hesitation), and at the correct speed rather than a fast idle, which it hasn't done for as long as I can remember (always thought it was due to the D cam & that they were all like that).

Before it got dark, I also took the opportunity to redo the rear silencer hanger, which I had bodged previously with some jubilee clips. However when the exhaust is raised to the correct height, the centre silencer hits the new rear footwells (the old ones had been 'adjusted' with a BFH but I' mnot prepared to do that to these new panels). A quickly made extension piece fore the rear strap was made from a cut down Halfords exhaust bracket & it will do for the time being until I re-hang & re-route the exhaust properly.

At the end of all this, the car was running very nicely & the exhaust was quiet again as it wasn't hitting everywhere so I decided to use the Amazon to transport my gf & I to a weekend of sailing (just the other side of Poole) rather than taking her VW Lupo. I am pleased to report that the Amazon performed very well, with plenty of 'go' at motorway speeds and over 211 miles used just 34.5 litres of fuel (about 28mpg).

A big thanks again to all for advice etc.

stumph · Oct 8th, 2007, 19:11

Glad it's all sorted! Nicely done

Wish I had the skills/knowledge to give mine a checkover. I am improving - I know what a carb looks like now

222s · Oct 8th, 2007, 23:42

Quote:

Originally Posted by stumph

Wish I had the skills/knowledge to give mine a checkover. I am improving - I know what a carb looks like now

Until earlier this year, all I'd done with carbs was to top up the dashpot oil & change air filters, so it's never too late to start learning!!

Oct 3rd, 2007, 19:13	#13
Clan Experienced Member Last Online: Today 13:59 Join Date: Jun 2007 Location: L/H side	what is the CO set to have you had it checked ? It is very easy to get it 12% and that will cause your problem , it should be around 2 or 3% CO when warm .( or less if the engine will idle ok ) __________________ My comments are only based on my opinions and vast experience .

Oct 4th, 2007, 10:05	#14
222s Amazoniste Last Online: Sep 19th, 2016 21:52 Join Date: Nov 2002 Location: Emsworth View Photos By: 222s	I've checked the movement of the damper pistons & they're fine. However the fuel level in the aft float bowl is about 10mm higher than in the forward one. Given the way in which the fuel reaches the carb, I think this might be a major part of the problem..... Anyhow - turns out that the float needle valve is very worn (pronounced step in its taper) so although sealing properly (so not leaking fuel out of the overflow), it closes when the fuel level is higher so it looks like the 'lost' fuel is overflowing through the main jet & thus through the carb. I swapped the needle valves around & it's now running better (but will of course fit new ones as soon as they arrive). Smells a lot less of petrol now too. Haven't checked the CO but am setting the mixture by lifting the damper pistons & checking the plugs. The front carb is running nicely so once the rear one is behaving, hopefully both running & fuel consumption will be back to normal! __________________ Paul - 1967 Amazon 222S B20 o/d Estate & 1961 A-H Sprite Mk2 948cc WANTED - For '67 Amazon estate - offside rear quarter, preferably new old stock. Last edited by 222s; Oct 4th, 2007 at 10:08.

Oct 8th, 2007, 16:59	#15
222s Amazoniste Last Online: Sep 19th, 2016 21:52 Join Date: Nov 2002 Location: Emsworth View Photos By: 222s	Took Friday afternon off work so would have more time to sort out the problems with the car. Still couldn't find any sign of fuel leaks, so turned my attention again to the carbs. Turns out that the choke on the aft carb unit has become a bit tempermental and was sticking open. Combined with the float jet issue, it looks like this was the cause of the 10mpg fuel consumption.... The choke had been fine when the carbs were adjusted the previous weekend, so must have stuck again since - this time though I greased all the carb linkages / spindles etc so that both chokes move smoothly now. Reset the mixture mainly on the at one, but the forward one also responded to a slight tweak, just using the lifting the carb pistons method (need to look at the plugs to check but haven't had time) & adjusted the idle screws. Now the engine idles very smoothly (also picks up without hesitation), and at the correct speed rather than a fast idle, which it hasn't done for as long as I can remember (always thought it was due to the D cam & that they were all like that). Before it got dark, I also took the opportunity to redo the rear silencer hanger, which I had bodged previously with some jubilee clips. However when the exhaust is raised to the correct height, the centre silencer hits the new rear footwells (the old ones had been 'adjusted' with a BFH but I' mnot prepared to do that to these new panels). A quickly made extension piece fore the rear strap was made from a cut down Halfords exhaust bracket & it will do for the time being until I re-hang & re-route the exhaust properly. At the end of all this, the car was running very nicely & the exhaust was quiet again as it wasn't hitting everywhere so I decided to use the Amazon to transport my gf & I to a weekend of sailing (just the other side of Poole) rather than taking her VW Lupo. I am pleased to report that the Amazon performed very well, with plenty of 'go' at motorway speeds and over 211 miles used just 34.5 litres of fuel (about 28mpg). A big thanks again to all for advice etc. __________________ Paul - 1967 Amazon 222S B20 o/d Estate & 1961 A-H Sprite Mk2 948cc WANTED - For '67 Amazon estate - offside rear quarter, preferably new old stock. Last edited by 222s; Oct 8th, 2007 at 17:01.

Oct 8th, 2007, 19:11	#16
stumph Member Last Online: Aug 30th, 2016 13:46 Join Date: Jun 2007 Location: reading	Glad it's all sorted! Nicely done Wish I had the skills/knowledge to give mine a checkover. I am improving - I know what a carb looks like now Last edited by stumph; Oct 8th, 2007 at 19:20.

Oct 3rd, 2007, 18:49	#12
Derek UK VOC Member Last Online: Today 13:07 Join Date: Jul 2006 Location: Chatham	If a dashpot piston is sticking, don't be tempted to clean it all up with Autosol. Petrol and a cloth only. The piston needs as little clearance as possible for it to work with the vacuum. If this is the problem it might also be the cause of your poor running and pinking a while back.

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