i have a 89 golf gti 16v, it wants to kangeroo first thing from a cold start..otherwise it runs sweet after a few mins and starts on the button
ive got a reasonble understanding of k jet..please dont chime in unless your SURE , as ive already had some bump steers :(
things ive checked ..
new injectors and o rings
fuel system pressure ok at 76psi
warm wur pressure ok at 49 psi
airbox flap height ok
5th inj sprays when cranking
new vac hoses, no other obvious air leaks
ive also used a air/fuel monitor and the readings check out at hot idle, cruise and when pulling hard
now , i need to ask few things
does idle mixture ajustment affect the mixture above idle
how does the airbox flap height affect things
any ideas what c/o or a/f ratio should be upon start up?
any sensible ideas on what it is and how to confirm it
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If you richen the idle you richen the air/fuel ratio throughout the whole calibration because you alter the angle between the arm holding the air-flow flap and the one controlling the amount of fuel being injected.As the flap rises,more fuel is injected.You say you have a working start injector but fast idle/warm-up fuel are contolled by a separate valve that allows air to by-pass the throttle plate;it almost sounds as tho' you have no or insufficient fuel on the warm-up circuit.I'm talking Ford but the system should be same.Remember the idle fuel screw works back to front;ie. you screw it in to richen the mixture(3mm.hex if I remember rightly).
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Yes, mixture adjustment via the 3mm allen screw modifies mixture throughout the rev range.
>>warm wur pressure ok at 49 psi
What is it when cold? It should be lower - allowing the plate to rise higher for a given airflow, giving a richer mixture. Does the warm up regulator have a vacuum connection?
Number_Cruncher
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its approx 10 psi cold..which is a little low , meaning it should be on the rich side
thing is i can ajust the warm pressure between 49-55psi and that ajusts the mixture at speed .ajusting the warm pressure doesnt seem to alter the cold pressure???
yes the wur has a vac conection, ive also tried another wur
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Well, at least it sounds like the warm up regulator is doing *something* - I'm not sure exactly what pressure it should give when cold, but you've obviously established that the thing is basically working.
>>5th inj sprays when cranking
Does it shut off again properly once the engine is running - I have seen lots of these which don't shut off.
Number_Cruncher
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>>yes the wur has a vac conection, ive also tried another wur
I forgot to ask, does changing the vacuum, perhaps using a mityvac change the warm up regulator pressure?
I guess, if you have tried two warm up regulators it does work properly, ...
Number_Cruncher
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cold should be 16psi at 50deg +- 3 psi so mines a little low, but that should be richer
not sure what the vac does...i "think" its enrichment under acceleration??? ive got no vac testing tools
spose i could disconect it and see
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cold should be 16psi at 50deg +- 3 psi so mines a little low, but that should be richer not sure what the vac does...i "think" its enrichment under acceleration??? ive got no vac testing tools spose i could disconect it and see
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Yes, you're right, it's a full load enrichment device - when there's no vacuum, the warm up regulator pressure drops further, and you get a richer mixture.
If the vacuum pipe to the warm up regulator is split, or the diaphragm inside the warm up regulator is leaky, then you might get lower regulator pressures than you should.
An over-rich mixture after start up can lead to chugging too - think faulty choke pull down diaphragms on mkII Cavaliers!
Number_Cruncher
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yeah i spose it could be too rich or too weak...id bet on weak
any ideas on what to do next...if i try to test for mixture , it takes several secondes to settle on the meter, by which time the symtoms wouldbr probably have cleared up on the road
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>>any ideas on what to do next...
Sorry Steve, my sadly meagre K Jetronic knowledge / memories have just about been exhausted.
Just to double check though, did you say that the cold start / fifth injector is shutting off OK - sometimes they dribble, emptying the contents of the accumulator into the manifold whenever there is fuel pressure in the line.
>>...id bet on weak
Ninety odd times out of a hundred, I would agree, but it's difficult enough to tell when the car's in front of you, never mind over the internet!
Near the top of the thread, you asked about the importance of the air flap height - the shape of the funnel effectively sets the mixture profile. For example, the funnel steepens at high flap openings - richening at high speed and load. You need to set the flap height so that this mixture compensation comes into play under the right engine operating conditions.
Good luck!
Number_Cruncher
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yeah i spose it could be too rich or too weak...id bet on weak any ideas on what to do next...if i try to test for mixture , it takes several secondes to settle on the meter, by which time the symtoms wouldbr probably have cleared up on the road
There are a couple of errors that can creep in in this part of the setup process:
1. You need to take the allen key out between adjustments, its weight effects the air flap mass.
2. You need to rev it to 3000 rpm between mixture changes, as rich residue in the exhaust takes time to blow out, as you've observed.
3. Some of the DIY CO meters (which i assume you are using) drift a lot with temperature, so short sharp measurments are needed, rather than leaving it connected the the exhaust for extended periods os time.
4. You need to set up the CO when the engine's hot, from your post above it sounds like you might be attempting it cold.
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With those engines it can also be worth swapping to the single electrode type spark plugs eg Champion C6YCC, and gapping them small (0.7mm) (assuming you're using multi-electrode plugs at the mo)
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mark why do you say that? how does single electrode ones change anything?
i run the standard 3 prong jobbies now, i noticed bosch super4's werent as good
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It's just that you can achieve the smaller gap needed easier with the single electrode plugs, the 3-electrode ones are not REALLY adjustable, and come with a relatively large gap.
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maybe i'll try some plugs
ive got a used metering head, dunno if thats worth swapping??
or im thinking maybe raise the flap slightly?? the manual says set the plate to x height , but no one says what would happen if it was higher or lower
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or im thinking maybe raise the flap slightly?? the manual says set the plate to x height , but no one says what would happen if it was higher or lower
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I did mention it a few posts further up. You need to set the flap height realtive to the funnel because the funnel changes its shape - abruptly at some points. The funnel gradient affects the relationship between *changes* in airflow and *changes* in fuel delivery. A steep gradient on the funnel will give more change in flap height for a given change in airflow - i.e., the mixture will richen (relatively) as airflow increases.
If you get the flap height wrong, the mixture profile, or mapping, for the engine is wrong. OK, you will be able to get the idle right using the little allen bolt, but thereafter, as soon as the flap moves away, you will be building up error.
I wouldn't suggest that you deliberatley try to mal-adjust the flap height.
Does the cold start injector cut-off properly?
Number_Cruncher
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^i agree with the above. It's much better in the long run to find the fault than put an offset in something else (usually the easiest adjustment) to try and compensate for said fault.
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number cruncher...i havent had chance to check the cold start today, i had to use the car .i will check it
does anyone have any figures for the pressure should sit at overnight?? it drops to 38 after shut off, but how long should it hold 38?? hours,days,weeks?
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update
i left the gauge on over night..after shut off it st at 38psi for several hours, this morning it was 0 psi, and priming the pump made it go to 30psi
i cant find specs on this, does it sound right..im thinking maybe it shouldnt drop to nothing
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Maybe I'm wrong but I was under the impression that fuel pressure on this system was meant to be nearer 90psi. The system does rely on fuel pressure, so if it is supposed to be around this figure it'd certainly explain your problem.....
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according to all the books ive got....yeah you are wrong
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I think that the pressure being kept up for a few hours is good. The pressure should sit below the pressure required for injection during this time.
However, there will always be small leaks through either the pressure regulating vavle in the distributor, or the non-return valve in the pump. Once the accumulator has emptied, then the pressure will drop rapidly.
I'm surprised that the pressure doesn't build back to 38 during priming. If you repeat the priming does the pressure build further - if so, does this help the post-start behaviour?
Number_Cruncher
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*************update for today************
tested the 5th inj, sprays nicley while cranking, shuts of nice with no dribbles .also sprays when blipping the thrrotle for the first 3-4 mins
ive also tried another wur...cold pressure is somewhat differant
does changing the warm wur pressure also change the cold pressue by the same amount or are they seperate to one another?
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