Wierd fuelling problems-Mended!
Turbo Mini Forums

Right-since putting the new motor back in I have managed to get out and put a few miles on it only to hit another problem vary soon.
I havent had car set up yet as I need to run it in first! After initially setting myself I was getting AFR of around 13.5 at idle, 12 under acceleration and lean over to 15-16 on the overrun, its always set off and pulled ok through the gears.
However now I seem to nearer 14 at idle, when you go to pull away normally in 1st,accelerate and it goes really lean. 16+ off the end of the gauge and it displays --- for a few seconds the engine stutters and then picks up and it goes ok, and a reading comes back, under acceleration it swings back to around to 11.5-12 pulls ok but its been a lot better, backing off to pull up to a junction often when warm it will go lean and stall when you pull up.

So far I have replaced the dash pot assembly as it seemed to be sticking at the bottom of its stroke, the new pot is off a n/a hif44 which is much smooth and spot on-but still no change

Pictures show the current jet setting, as shown my carb has no float chamber vent pipe as its factory blanked but has all other connections. I have made a few adjustments with mixture(rich) which has mildly improved things but still no where near as good as it was at the start.
Today I have teed a fuel pressure gauge between carb/reg and had a little run with it under the wiper, 4 psi at idle and 4 psi above boost, no drop off of pressure. I currently run 3 in 1 oil in the dashpot, std bdd needle and 2 dashpot springs wound inside each other and the part throttle lean off is not blocked off as it always seemed to run really well without

Anyone any ideas where to look before pulling the carb back off and stripping it again.







Cheers

Oli

Edited by oli79 on 6th Jan, 2011.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

we clamped the part throttle lean off with some maul grips on the van, might be worth giving it a try to see if it helps.

has the jet got any unrestricted up/down movement in it ?

http://www.fishfight.net/

I would definitely block the part throttle pipe, had similar issues on mine years ago, all solved by the blocking the pipe.

Your jet looks quite low/rich, what needle are you using? has it been modified?

Just remember you may need to adjust after blocking the part throttle pipe.

Also, try a thicker oil, I found 3in1 too thin for turbo use.

Hope you sort it mate.

Edited by Kean on 2nd Jan, 2011.

Thats a very good point, I did make a solid jet holder for this when I rebuilt and there was no movement then-but it is a definite to check, just wanted to see if people had any ideas while the carb is still on and everything in is once piece

cheers

oli

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Hi-Thanks will have a try at that tommorow and also going to put some new fuel in, although whats in is not very old its worth a try to eliminate it. Jet is a bit low, as I say I have wound it a bit richer today to try it, its a standard unmoded needle which to be fair has been fine so far-running in at 7-8 psi.

Thanks for the comments

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Todays non progress, carb off the car stripped and checked, only thing amiss seemed to be the vac advance pipe(which is blanked as above) was loose in the carb body so pulled out, tapped m4 and put in a short bolt+threadlock+fibre washer, cleaned and blew out and inspected each component of carb nothing I can see wrong. Refit carb and its the same. Stripped fuel reg to check-clean as a whistle, diaphram perfect. No change, checked all hoses and blocked off connection to servo and checked all connection to inlet manifold-no change

So went back to my initial settings where the car ran really well which is:-1 dashpot spring and 20/50 engine oil in dp and open lean off pipe set at 13 afr at idle it will go to 12 under power but often start to lean over to 13-13.5 even with foot down and silly lean on the over run 16+ and gauge displays --- for a second, still goes 16+ lean and bogs when pulling away.

With lean off clamped its better but only because its rich all the time 11.5 at idle so leaned it off a touch, now 13 at idle and 12 under power, seems to lean out less under throttle but still silly lean overrun 16+, still will cut out on the overrun and still leans and bogs when pulling away. Seems hesistant generally

Managed to get it after a short run and pulled up and it was sat 13.5 idle then without touching it it would go lean over a few seconds start to bog and then pickup again. Now sit and blip revs to 3500-4000 ish goes rich 12ish instantly and then shoots round to 16+ and stutters and either dies or just about keeps going, tried this 3 times with same result then tried it again but pulled the choke as it got to 16-engine picks straight back up and shoots back over to 12-13.

Doing my head in as all I did initally was set idle at 14 ish and it would sit steady at around 13.5 at cruise, 11.5/12 under power and overrun never went off the scale, it pulled great and didnt cut out. Maybe need to go back and check everything.

Anyone know does a standard 90's carbed mini fuel tank have any sort of internal filter?

Cheers

Oli

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Get it on a rolling road and get it setup properly

Yeah-I think that may be the next logical conclusion, what I cant understand is that it at least ran really quite well at the start and then seems suddenly shit, Im not trying to set it up, im trying to sort any potential problems and get it back to this initial running ok,and more importantly get it run in, before forking out for rr time, but it may be the only answer.

cheers

oli

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

If it's that intermittent you run the risk the of doing serious and expensive damage to your new engine.

Yep-also my biggest concern

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

Sorted -Not fuel at all-it was the ignition leads breaking down,I could tell something was amiss!, the standard mj ones and not very old but it could be because a couple were bent at the top behind the IC and pipework, so new angled leads, plugs cleaned and everything is back to normal.Its odd I would have thought the ignition breaking down would read as going rich on the afr gauge as more unburnt fuel went into the exhaust but obviously not! Glad I got it sorted before deciding to RR anyhow, will get it booked in soon me thinks.

Cheers

Oli

Edited by oli79 on 6th Jan, 2011.

On 5th Oct, 2014 Shauna said:
What that's crazy, you go commando hahaha! How heavy is your helmet ?

also use 80 or 90 weight gearbox oil not 20/50 as the thicker oil is more stable when it gets hot unlike multigrade making tuning easier

always looking for them bigger bunches of bannanas