running lean but only after 7sec's

[Mr 5]

been haveing a play on my private test track recently and found that from a standing start to 80ish mph the car runs fine (AFR reads 12.2-12.4)

but...after you've spanked it up to there the AFR climbs....fast! like 16...17....then backed off quickly to save meltdown,tried again but this time from 60,foot to the boards in 5th and after 7secs the afr started climbing again....

never had a fuel problem befor,but have had a regulator leak so changed it.

clearly its getting starved,is the carb emptying too fast ? if so,why now? had a new fule pump not long befor xmas.

just wondering where to look 1st

[raj]

sorry to hi-jack but does has anyone ever teed the fuel pipe off from where it fits to the carb? sending the teed off bit directly to the carb fuel camber? i recall AVE doing something like this to stop his camber from emptying too quick..?

[tiff_lee]

i recall AVE doing something like this to stop his camber from emptying too quick..?

Yes it is mentioned about 3/4 of the way down this thread https://www.rtoc.org/boards/showthread.php?t=4734
and there is an image on the right hand side of the setup.

Unfortunately in his comments there is a link to the setup he created but it is now dead, not sure if the link was purely the image on the right or something more.

[Rob@Backyardracing]

Mr 5 you will be emptying your carb of fuel are you on the standard 1.7mm needle? if so you can open this out with care drilling to a 2mm.. Your could check your fuel pressure to carb just to be clear all is well with the fuel reg etc. should be 4psi base and above boost reading from where reg vac ref pipe is T-peaced from on your system, normaly carb top... If you still run lean with a 2mm try swaping your ref pipe for the reg to the compressor outlet on the turbo (make sure its at the end of the housing rather than halfway round the snail). See if the extra 1 or 2 psi boost at this area helps with fuel pressure before you jump right in to drilling a 2.1 and so on needle and trying to seal it.

Ive also tried what ave did a few years ago on my old gt, it does work but you need to set it to a T as you can easily over fuel and give bad performance.. You just need to find the perfect restrictor to what suits your set up...

[Mr 5]

cheers rob, the carbs been fettled befor i bought the car,never had any problems previously, only noticed it since i changed the rgeulator so think il change that 1st. the one i put on wasnt new so think il get a new one,

how can i check the pressure? as in what gauge?would a old boost gauge do the job?

[TommyB]

I've used an old oil pressure guage before, to check a high pressure system.

[Mr 5]

well.... went to renault,got a brand new fuel filter....didnt help

went back and got a regulator ....made it worse! foot to the boards in 3rd only lasts maybe 3secs befor AFR rises to 15-16-17...

getting annoying now,fuel pumps quite new so dont think its that, just dont understand what the problem is

should i try and drill out the needle to 2mm? will this let the carb fill up faster am guessing?

[olidaviesuk]

Have you got a compressor, or tyre inflater with decent gauge? easy way to check if the pump/regulator side of things are working properly (as I had similar probs recently - mine is now running A1 so if you get similar results then can rule out the pump and reg, and so point to probs with the carb.)

Put 1 bar of pressure onto the hose that goes to the regulator, you'll need to remove this hose from the lobster (from front of car, left hand hose, back of the double T Piece)

Get a one litre container, and remove the fuel hose from the carb. you are measuring how long it takes to flow a litre of fuel with one bar of air pressure at the regulator.

Get some mates, one with a stopwatch and one who is handy with electrics as you need to bridge the fuel pump relay..

A standard (PH1) pump will flow a litre inbetween 30-40 secs so if your system is flowing this then its in fairly good order..

Obviously if you aren't comfortable with any of this then don't do it as it involves flowing a lot of fuel about which isn't the cleverest thing unless you are really careful.

[Scoff]

you need to be measuring fuel pressure rarther than guessing stuff. some will cringe but there's no harm in using an old boost gauge, use fuel hose for the pipework and rig the gauge infront of your windscreen, cable-tie it to a wiper or something. it needs T-ing in just before the carb. Go for a test run, you should have 4psi *more* fuel pressure than carb top boost pressure. If the pressure drops off then its a pump/filter/lines/regulator issue. If pressure stays healthy then perhaps you've reached the limit of the 1.7 needle valve, usually comes up at around 200hp, in whice case 2mm will help. Finally, I hope your not using an LC-1, one of the faults I used to see with those was random leaning off! If afr actually gets to 15:1 then the engine will feel very hesitant, any leaner and it will missfire.

[Adam 005]

have you checked the filter behind the fuel inlet pipe on the carb

[Mr 5]

Have you got a compressor, or tyre inflater with decent gauge? easy way to check if the pump/regulator side of things are working properly (as I had similar probs recently - mine is now running A1 so if you get similar results then can rule out the pump and reg, and so point to probs with the carb.)

Put 1 bar of pressure onto the hose that goes to the regulator, you'll need to remove this hose from the lobster (from front of car, left hand hose, back of the double T Piece)

Get a one litre container, and remove the fuel hose from the carb. you are measuring how long it takes to flow a litre of fuel with one bar of air pressure at the regulator.

Get some mates, one with a stopwatch and one who is handy with electrics as you need to bridge the fuel pump relay..

A standard (PH1) pump will flow a litre inbetween 30-40 secs so if your system is flowing this then its in fairly good order..

Obviously if you aren't comfortable with any of this then don't do it as it involves flowing a lot of fuel about which isn't the cleverest thing unless you are really careful.

cheers pal,shall try tommorow

so if it takes longer than that am guessing its the pump,if all that is gravy then i need to investigate carb?

if its pump its a easy fix,but carb....i have feck all idea on those swines!

[olidaviesuk]

Yeah, If you haven't got a fuel pressure gauge then what I said can give you a fairly good indication that your fuel system is in fairly good order. You really want to be doing what scoff suggests, but if you haven't got the gauges etc then is pretty difficult to do that.
My method doesn't take into account the fuel pumps ability to hold and maintain pressure, it just gives you an indication that the problem is in that area or somewhere else..

you need to be measuring fuel pressure rarther than guessing stuff. some will cringe but there's no harm in using an old boost gauge, use fuel hose for the pipework and rig the gauge infront of your windscreen, cable-tie it to a wiper or something. it needs T-ing in just before the carb. Go for a test run, you should have 4psi *more* fuel pressure than carb top boost pressure. If the pressure drops off then its a pump/filter/lines/regulator issue. If pressure stays healthy then perhaps you've reached the limit of the 1.7 needle valve, usually comes up at around 200hp, in whice case 2mm will help. Finally, I hope your not using an LC-1, one of the faults I used to see with those was random leaning off! If afr actually gets to 15:1 then the engine will feel very hesitant, any leaner and it will missfire.

[Brigsy]

If you need the wideband gauge checking, pop down & try my lm1 on it mate

[Mr 5]

you need to be measuring fuel pressure rarther than guessing stuff. some will cringe but there's no harm in using an old boost gauge, use fuel hose for the pipework and rig the gauge infront of your windscreen, cable-tie it to a wiper or something. it needs T-ing in just before the carb. Go for a test run, you should have 4psi *more* fuel pressure than carb top boost pressure. If the pressure drops off then its a pump/filter/lines/regulator issue. If pressure stays healthy then perhaps you've reached the limit of the 1.7 needle valve, usually comes up at around 200hp, in whice case 2mm will help. Finally, I hope your not using an LC-1, one of the faults I used to see with those was random leaning off! If afr actually gets to 15:1 then the engine will feel very hesitant, any leaner and it will missfire.

got it in one mate ! i wasnt paying much attention to the wideband when it 1st started happenin,just felt like it was holding back alot,like i had hit a head on wind or something,then when watching the wideband whenever it held back the AFR was rising above 15.

il try the boost gauge plumbed in 1st and see how that goes befor i start blowing through the fuel lines,also check the filter i didnt know existed (cheers adam )

just seems strange that this happened suddenly then when i changed the main fuel filter and reg it seems to have made it worse.

like i said the car runs fine apart from when you give it some and it holds back,all gauges read normal ....

[car.crash]

you can buy 2mm needle valves on ebay germany, straight fit and seal properly but some drilled out 1.7 versions dont always seal.

[Mr 5]

If you need the wideband gauge checking, pop down & try my lm1 on it mate

cheers mate,i may well do that

[Logg]

I had a problem just like this and tried all sorts to fix it in the end it turned out just to be a split in the pipe from the carb top to the regulator!

[Rob@Backyardracing]

Also the Porsche 356/ landrover/ and old pugs all run a 2mm solex needles... They do work but i found them to run lumpy on normal driving conditions...

[Rob@Backyardracing]

Oh actualy i ran 7psi fuel pressure on base tho... so may run fine with the normal 4 over...

[Scoff]

I ran +6psi, a 2.3mm needle and still emptied the bowl in 4th gear!

split in reference pipe and blocked filter behind brass inlet port are good suggestions

just while we're on the subject, it's good practice to run the reference pipe straight off the turbo compressor housing, or before the intercooler at least. it should yeild an extra couple of psi fuel pressure while on boost

[Rob@Backyardracing]

Emptying 2.3mm was the days.......

[THE MASTER]

i run three gauges above carb and below for boost now my below carb is always lower than above carb for boost as it should be,
now my third gauge is for feul . that is always above the boost presure above the carb

simmple innit

[Rob@Backyardracing]

i run three gauges above carb and below for boost now my below carb is always lower than above carb for boost as it should be,
now my third gauge is for feul . that is always above the boost presure above the carb

simmple innit

Spot on col thats because your reg is prob T`d from above the carb, if you t the reg from comp housing you gain a couple as from pressure drop over cooler and boost pipes thus a couple more psi fuel pressure, which may save you from drilling that extra MM on the needle.....

[Mr 5]

thanks for all the comment lads,il start 1st thing in the morning,thinking it may be the vacuum hose since it drives fine unless under constant load,fingers crossed its a easy fix!

[Mr 5]

where can i take a regulator feed from on the comp housing? never noticed any hoses on or aroun there other than oil/water?

[J$£5GTT]

sorry to hijack,but im trying to understand all these pipes to pipes
etc..an i have no idea what im on about... but found this picture
in the articles section-

[THE MASTER]

Spot on col thats because your reg is prob T`d from above the carb, if you t the reg from comp housing you gain a couple as from pressure drop over cooler and boost pipes thus a couple more psi fuel pressure, which may save you from drilling that extra MM on the needle.....

the float camber (above carb)should be at a higher pressure that the mani pressure (below carb)and if the fuel pressure is above the above carb then youl always be puuting fuel into the carb

yes i know i talk in riddles but its worth working out

[Rob@Backyardracing]

Ok justin, thats a (nos) solenoid that will operate on an over boost swtich i guess, the bolt it goes to is direct to the fuel float chamber view a banjo bolt.. this will supply extra fuel to the bowl to stop the carb or bowl from emptying of fuel... The prob with Avs set up there it has no restrictor unless a small hole in a pipe which we cant see, the carb will fill faster than your car can empty it. so you need to set a the flow up best you can...

[Logg]

you can buy 2mm needle valves on ebay germany, straight fit and seal properly but some drilled out 1.7 versions dont always seal.

That you can as well as 2.5mm needle valves

[Rob@Backyardracing]

the float camber (above carb)should be at a higher pressure that the mani pressure (below carb)and if the fuel pressure is above the above carb then youl always be puuting fuel into the carb

yes i know i talk in riddles but its worth working out

but some of us like that tad more fuel pressure thus take your FPR ref pipe from the comp housing (correct area of course)....

[THE MASTER]

but some of us like that tad more fuel pressure thus take your FPR ref pipe from the comp housing (correct area of course)....

it's all about keeping the boat floating at the right level

[Rob@Backyardracing]

it's all about keeping the boat floating at the right level

i see iceburgs.............................

[Scoff]

That you can as well as 2.5mm needle valves

2.5mm will not work, 2.3mm is the limit for most that have experimented. I could not go any bigger without fuel pressure pushing the valve open and flooding the bowl at idle.

[Scoff]

where can i take a regulator feed from on the comp housing? never noticed any hoses on or aroun there other than oil/water?

typically only found on bigger compressors, some T25 and most T28 / T3 have a 1/8 bsp hole that will accept a hose tail.

[THE MASTER]

i see iceburgs.............................

the tittanic had a sister ship and that sunck aswell

[Logg]

2.5mm will not work, 2.3mm is the limit for most that have experimented. I could not go any bigger without fuel pressure pushing the valve open and flooding the bowl at idle.

Oh well it was worth a thought!

I wonder if there's any way of increasing the buoyancy of the float to solve that issue?

Could using double washers on the needle valve so it sit's lower into the bowl help increase the pressure the float has to hold it shut?

[Mr 5]

ok, ha dcarb to fits today, found the little filter in the car (looks like a yellow tube?)clean and fine, while i was at it i removed the choke flap and blocked the holes,now when i start the car its mega mega rich,started to misfire and cut out....clearly i have done something,but what...

from one problem arrises another,happy saturday

[Rob@Backyardracing]

Oh well it was worth a thought!

I wonder if there's any way of increasing the buoyancy of the float to solve that issue?

Could using double washers on the needle valve so it sit's lower into the bowl help increase the pressure the float has to hold it shut?

Double washers still wont seal a 2.5....

[Rob@Backyardracing]

ok, ha dcarb to fits today, found the little filter in the car (looks like a yellow tube?)clean and fine, while i was at it i removed the choke flap and blocked the holes,now when i start the car its mega mega rich,started to misfire and cut out....clearly i have done something,but what...

from one problem arrises another,happy saturday

When you say holes which ones have you blocked? the small filter in the carb inlet i normaly bin.

[Mr 5]

taken carb apart again,the carb itself is full of fuel?! dont no why,havent touched anything to do with the carb base?

holes i filled are the two eitherside where the rod for the choke flap went through the carb,

[Logg]

Double washers still wont seal a 2.5....

Why is that?

Just down to the sheer volume of fuel that the 2.5 can flow?

If it's a brand new 2.5 mm needle valve there should be a good seal unlike a re drilled 1.7mm one shouldn't there!

I just thought that if the needle valve sat a bit lower the float might have a bit more pressure to hold the needle valve shut when the bowl was full!

[Scoff]

Oh well it was worth a thought!

I wonder if there's any way of increasing the buoyancy of the float to solve that issue?

Could using double washers on the needle valve so it sit's lower into the bowl help increase the pressure the float has to hold it shut?

yep, we tried all that business short of making the float more buoyant as rob says I can't think of another mechanical solution. a rising rate regulator combined with a lesser sized needle might help, or it may just have the same bog-down-after-fast-gear-change side effect that the bigger needle valve sometimes has. Although, I never suffered that on my car even at 2.4mm, just that the valve would not regulate properly at idle.

[Mr 5]

ok flooding problem sorted,musnt have sealed the gap between the resevoir properly,sorted and running/idleing fine,still lean tho,

the needle,am assuming thats the little valve above the float?

[Scoff]

logg, yes, sheer fuel pressure pushes it open much past 2.3mm, it can't regulate any more.

[Scoff]

ok flooding problem sorted,musnt have sealed the gap between the resevoir properly,sorted and running/idleing fine,still lean tho,

the needle,am assuming thats the little valve above the float?

yes, thats it. not sure if anyone has asked but what sort of boost are you running ? or better still do you know how much power it makes ? If it's much less than 200hp then the needle jet will not be too small, it will be a fault else where.

[Mr 5]

yes, thats it. not sure if anyone has asked but what sort of boost are you running ? or better still do you know how much power it makes ? If it's much less than 200hp then the needle jet will not be too small, it will be a fault else where.

running 1.2bar at manifold,makes 210bhp, only got RR'd just befor xmas and was fine then(AFR/graphs etc) and nothings been done mechanically since then,thats why i thought it was something failing,

so far iv checked carb filter - fine
changed regulator for a used one,then a new one - seems ok
fitted new ph1 pump just befor RR - seems ok

like i say it appears like its just running out of fuel,like its emptying the bowl too quick,just not sure why all of a sudden,drives as befor at all other times apart from when my right foot gets abit heavy.

going to check vac pipe from regulator now,after i put the new reg on yesterday it seemed to run lean quicker than it did withj the old one on....

[Mr 5]

btw scoff....can i have your car please ?

[Logg]

Ok thanks Rob and Scoff!

Sorry Mr 5 for going off your topic!

Still haven't fitted those lights I got off you!

Might have to start my own thread later as I've more questions!

[Scoff]

btw scoff....can i have your car please ?

bah you wouldn't want it, not half as cool as yours. mines a bit rustic, sort of function over style

[Maka]

does anyone have the link to the 2mm needle jets on german ebay?
i cant find them for love or money! i cant find them for the carb either