View Full Version : Urgent help needed!
mikey_r5gtt
07-10-2009, 13:59
Hi guys, Ive got a prob.
My car is in the garage at the mo getting the fueling sorted out. When it was first put on the rollers is was running uber lean (18:1) now that they've changed the carb jets its running fine up to 3k revs then spikes massivly and runs lean, its as if the carb is getting starved.
I haven't got any special mods just induction kit, exhaust, t25 turbo and about 17psi of boost.
Its getting worked on now so if anyone couls shed any light and save me a few quid in labour charges that would be good.
Thanks in advance
car.crash
07-10-2009, 14:05
It could be emptying the float chamber. What exactly did the garage do to the carb?
Id say the carb probably needs jetting correctly. Also check the fuel pressure & fpr is working correctly & no splits in the reference pipe.
mikey_r5gtt
07-10-2009, 14:12
As far as I know his has just uprated the carb jets with the set supplied from KTR.
First post!
Yep we have opened up the secondarys to 1.3mm put a 130main jet in the carb as well as a 1.0 ac we opened up the needle valve in the float chamber to 2.0mm to try and stop the carb emptying its self.
The fuel pressure is 4 psi at idle and rises at 4psi above boost all the way. We just stripped and cleaned every part of the carb to check there were no tears in any of the seals.
There are no vac leaks and everyting is plumbed in correctly but it hits 3500 rpm now and just shoots up real lean when it came in it started off at 15:1 afr from 1700rpm and quickly rose to 18:1 by 3000 rpm. now it runs 12.3:1-12.5:1 till 3500 under wot then it goes all wrong we are a bit stumped now.
We have never had problems like this with them, we usually just change the main jet and air corrector and with that we can get them running fine.
Any ideas lads?
Btw its Matt at Reidy remaps / Performance 3000 here. any ideas by text also welcomed 07709453760
What size venturi is the carb? Is it a bored out 'grp a' Job?
New poster! (less than 10 posts)
What size venturi is the carb? Is it a bored out 'grp a' Job?
no its stock.
Its really quite odd we thought it may be the fuel pump but the fuel pressure goes up so there must be enough flow, but you never know it could still be the problem.
It always does it at the same point?
Jimmy_GTT
08-10-2009, 12:18
New poster! (less than 10 posts)
no its stock.
Its really quite odd we thought it may be the fuel pump but the fuel pressure goes up so there must be enough flow, but you never know it could still be the problem.
It always does it at the same point?
Have you checked the 2nd stage at the carb body?
Is it standard 1.0?
I was just going to say have you checked the 2nd stage as it doesn't seem as though as boost is coming on it is fueling enough.
As above what size is the non removable 2nd stage jet??
Jimmy_GTT
08-10-2009, 12:27
Or even the little membrane has a hole and the 2nd stage doesn't open at all.
Or the neadle of this membrane is stuck.
I have never seen a carb overhaul kit which contains a correct size of this part.
if it suddenly starts going lean at about 3500rpm, then doesnt this coincide with 'full boost'? if so, i'd suggest that you pull the pipe off the enrichment circuit breather, as i suspect you may have it either blocked or going to boost.- which is wrong.
Did opening the needle to 2mm move the problem further up the rev range?
Likewise, if the boost is dropped does the lean-off occur further up ?
If the bigger needle helped, and/or the lower boost made the lean off occur later then the level in the bowl must still be dropping. If it made no difference then it must be an enricher problem like the guys say.
New poster! (less than 10 posts)
I was just going to say have you checked the 2nd stage as it doesn't seem as though as boost is coming on it is fueling enough.
As above what size is the non removable 2nd stage jet??
the second stage jet is 1.4mm now we just opened it up again from 1.3 before it was 1.0mm but still same problem. maybe the carb needs a new overhaul kit thats pretty much all we can think of but everything looks in good condition now but it does seem like the second stage fueling isnt working as if we change the first and main jets the fueling changes but no matter what we do to the second stage nothing happens.
New poster! (less than 10 posts)
if it suddenly starts going lean at about 3500rpm, then doesnt this coincide with 'full boost'? if so, i'd suggest that you pull the pipe off the enrichment circuit breather, as i suspect you may have it either blocked or going to boost.- which is wrong.
its not blocked and its not going to boost we checked that its just sat down by the gear box, open to atomosphere.
New poster! (less than 10 posts)
Did opening the needle to 2mm move the problem further up the rev range?
Likewise, if the boost is dropped does the lean-off occur further up ?
If the bigger needle helped, and/or the lower boost made the lean off occur later then the level in the bowl must still be dropping. If it made no difference then it must be an enricher problem like the guys say.
It didnt really move it much up the range maybe 100-200rpm at max il try lowering the boost but its happening at only 8-10psi of boost anyway.
cheers for all the thoughts guys.
Not sure if its been answered but does it only lean off once boost comes in strong, or does it fuel fine initially and only lean off at a particular rpm ? I know you mentioned 3000rpm's ish but I don't know how laggy the turbo is.
New poster! (less than 10 posts)
Not sure if its been answered but does it only lean off once boost comes in strong, or does it fuel fine initially and only lean off at a particular rpm ? I know you mentioned 3000rpm's ish but I don't know how laggy the turbo is.
it leans off at around 8-10psi of boost around 3200-3500 by 4000rpm its a good 16:1 afr now.
Oh, so if its leaning the instant that boost comes up then its an enricher problem.
Either the 2nd stage isn't working (stuck, blocked, holed diaphram, etc) or the carb may be assembled wrong. It's possible to screw the 2 triangle enricher sections (1st and 2nd stages) onto the removable section in the wrong order. IE, long pointy 2nd stage (with brass tail) should be closest to the bulkhead, not the short flat 1st stage section. The screw pattern is the same on both enricher sections, if you see what I mean.
Failing all that then maybe the body of the carb itself has some blockage. Might be time to try a different body.
just edited that for a typo..
Chris Hebden
08-10-2009, 13:27
Oh, so if its leaning the instant that boost comes up then its an enricher problem.
Either the 2nd stage isn't working (stuck, blocked, holed diaphram, etc) or the carb may be assembled wrong. It's possible to screw the 2 triangle enricher sections (1st and 2nd stages) onto the removable section in the wrong order. IE, long pointy 2nd stage (with brass tail) should be closest to the bulkhead, not the short flat 1st stage section. The screw pattern is the same on both enricher sections, if you see what I mean.
Failing all that then maybe the body of the carb itself has some blockage. Might be time to try a different body.
Scoff, could you elaborate a little futher on the middle paragraph as i am having the same issues with mine (wont richen on boost) cheers Chris
Jimmy_GTT
08-10-2009, 13:31
Have you checked thee membrane I'm talking about?
http://www.renaultclub.hu/membrane.jpg
Maybe it is tucked or has a hole on it.
Jimmy_GTT
08-10-2009, 13:38
This is the normal position:
http://old.rtoc.org/articles/i/autofolder/XKCYKYVXHJPZGZKXVPYI.jpg
Chris Hebden
08-10-2009, 13:41
This is the normal position:
http://old.rtoc.org/articles/i/autofolder/XKCYKYVXHJPZGZKXVPYI.jpg
So what Scoff is saying, its possible to swap the bigger part (brass tongue) with the smaller cap on the left?
New poster! (less than 10 posts)
we found the issue it was a problem with a pipe to the fpr, now we have lots of fuel time to go to 1.2 main jet and back to a larger ac.
thanks for the help guys
Matt
I thought you had measured fuel pressure ? Glad its working anyway.
Chris Hebden
08-10-2009, 14:24
Glad you got yours working fine! I have made a step forward in that my reference pipe for the enricher was blocked, the fuelling is pretty spot on at WOT BUT....... there is a funny lean spot at 3000rpm where it drops down in the16's afr and then goes straight back up to 12's as the boost comes in strong, any suggestions!?
ps- sorry for the hijack!
New poster! (less than 10 posts)
I thought you had measured fuel pressure ? Glad its working anyway.
we had measured fuel pressure but after removing all the pipes and refitting them on the fpr the problem was solved? its weird but we didnt do anything else.
I just put the stock ac back in and we now have 12:1 - 12.2:1 on boost but 15:1 off boost so think we need to play with the first stages to get it a bit richer also idle is really lean now and the mixture screw only lets us adjust between 16:1 and 20:1 at idle.
gotta love the good old carbs. she just made 158ftlbs and 138bhp at 5000 rpm we havent gone higher yet as we are still sorting the fueling and also we ran out of threads on the actuator and so are limited to 15-16 psi of boost at the moment.
New poster! (less than 10 posts)
Does anyone think going to a 1.2mm first stage might solve the lack of fuel at idle and up till 3000 rpm we just cant seem to get the car to idle sensibly now it sits around 16-17:1 the mixture screw cant seem to get it lower we went to a 1.4 main jet with the stock air corrector and we now have 11.8:1 afr on boost which leaves head room for more boost and off boost is 14.2:1.
any thoughts welcomed just want to get the car sorted asap.
cheers guys.
New poster! (less than 10 posts)
just a quick update.
now got 13.4:1 till boost comes on with a 1.2mm first stage and then 11.8:1 till 6000 rpm but still a crap idle, the carb may be hot so will test in the morning and hopefully have it sorted otherswise larger idle jet wil be needed.
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