Hi there, I have installed another K-jetronic fuel system (metering head, airbox, WUR, pipes, ...) on my 16V (kr) to test it. This system was taken ou of the factory in 1989 and has been stored until today. So the system was never used since 1989. I've put the injectors from my previous system on it (cause I'm sure they work correctly). I've bridged the pump relay to test the system without the car running and with injectors in transparent bottles. The issue: With the pump activated, the injectors shouldn't spray fuel without the air flow plate being lifted. But they do, all 4 injectors spray a small amount of fuel even with the plate in its resting position ! Is the fuel pressure to high? Is there a problem in the metering head? I've check the pressure regulator (bolt on side of metering head) and it's really brand new.
you really need to get a set of pressure gauges to diagnose k-jet, otherwise its just a guessing game check the flap is flush with the narrowest part of the cone towards the front, if not adjust the spring to suit. make sure the flap will push downwards thru the hole without sticking, and hold it to the light to ensure the disc is central in the hole. take the fuel metering head off the air flap assembly and check the plunger in the bottom, it should move smoothly without sticking. be aware that if the pressure is still high it can be pushed out the bottom on some, usually there is a retaining spring to stop it coming out too far though. with the injectors i would think about purchasing some new mecedes brass ones from ebay, that way you know the entire system is nice and new
Thanks for the quick reply! I have the gauge set and tried it out just now for the first time. Control pressure (valve open) after few minutes running: 3.6 bar System pressure (valve closed): 4,9 bar Engines idles perfectly but it doesn't run like it's supposed to, I can hear it. (Something else bothers me, there's a valve ticking loudly. Never had that before. The engine didn't run since over a month, hydraulic tappet empty? ) Sorry for my english, I'm from Belgium. The Mercedes brass injectors aren't air shrouded (improves the mixture formation at idle + less fuel consumption) and I prefer using genuine VAG parts when it comes to important mechanical stuff
The car starts really difficultly, and when it does, it runs like crap. The problem is that the spark plugs get drowned with fuel, all of them. And when I take out the spark plugs it looks as if the pistons are moist, sometimes there's even smoke (fuel vapor?) coming out of the spark plug hole. So I'm thinking the following, it would be nice to have some more opinions on this before I dismantle the distributor: as I said in my 1st post, the injectors spray fuel even when the air flap is in its resting position. So I'm thinking the spark plugs get wet even before the car starts ?? The only part that lets fuel go to the injectors is the plunger in the metering head so I'm guessing it's not falling back to it's resting position and letting some fuel go to the injectors. The control pressure is 3.6 bar (as I measured), the injectors open between 3.5 and 4.1 bar. So I think the metering head is letting fuel to the injectors when it shouldn't. You guys have any other thoughts?? The air flap is centered and moves up and down smoothly with even pressure. I even feel the plunger falling back on the arm, which contradicts what I said above...:-S
I've made a picture before installing the system in my car. I'll make a better one asap. If the plunger is letting fuel go to the lines, in resting position, that would mean that the plate is sitting to high in the big cone. I inspected the plate several times today and it doesn't seem to be sitting to high..
the air shrouding makes next to no difference, beleive me i have tried both types on my own kr and abf engines. they are still genuine bosch and are exactly the same as early mk1 1.6 gti injectors except they are made of brass. Its up to you though! as i say, take the metering head off the air flap and pysically check the metering pin in the bottom, make sure its smooth in operation and doesnt stick. if it does undo the nut around the base so you can remove the retaining spring (if it has one) then carefully withdraw the pin. clean any dirt off with fresh petrol till its spotless, and clean out the hole it came from again with fresh petrol, take care not to get any grit in here. if the pin is heavily scored then the metering head is scrap, get another one
Ok, I will check the metering pin in the head. Are you sure the opening pressure of the brass injectors are the same as 16V kr ones (somewhere between 3.5 and 4.1 bar if I'm not mistaking) ? Because I've read that early type injectors have a lower opening pressure (around 2.7 bars). Anyway, I'll check the metering head first, cause I think the problem should be in there somewhere. I'll keep you posted, thanks fr the help!
well i never had any 'premature spray' problems with the mercedes injectors thats for sure you might find the proper vw ones are available for a better price in your country, the main reason we go for the brass ones is they're nearly half the price of the oem steel ones! the fact ALL the injectors are incontinent would suggest its a metering head issue rather than an injector problem agreed oh and if you need check my sig there are a couple great testing pdfs for the kjet system, a bentley one and a saab one edit: im not sure if the opening pressure is actually different, because the 1.8 8v metering head is the same part regardless of if it has early or late injectors?
premature spray lol The 16V kr ones (Bosch 0 437 502 041, VAG 049133551A) are €75 tops here (60GBP). I had allready checked out your signature, some great stuff in there! The Peugeot k-jet manual is very usefull (k-jetfactorymanual.pdf). I have some great K-jet manuals as well but some of them are in french, german, dutch (official languages is belgium so I understand all 3). The german ones are official VAG manuals. I can always send them to you if you'd like. Another good one: http://www.dmcnews.com/Techsection/Bosch K-Jetronic Fuel Injection Manual - boschtech-12d.pdf Ok, i'll check that metering head now.
I looked under the metering head and took out the plunger, this is what I found: 1 2 3 4 All seems pretty good to me. I pushed the plunger up and down in the head before taking it out, it moved up and down easily and with a damped motion. I don't know what to do anymore... Any ideas?
as long as the flap is flush as per this pic: http://www.race.nangreaves.com/golf/FU01/ch5.1.2.html I cant see what else it could be except for worn injectors, as the system and control pressures seem fine to me (was 3.6bar measured when the car was fully warmed up?) cant see how all 4 could be the same though, is it possible to get hold of some injectors off another car just to double check?
It seems to me the flap is flush on 1 side but a little bit lower on the other side. In the Peugeot manual it says that it can be lower by 0.5mm. That's exactly how much it seems lower, but of course it's not easy to tell this with the eye. I have to admit, I don't realy like to screw around with the flap and start bending the spring and stuff. Could be even worse after, no ? Seems as if that is my last option though.... I have tried with the injectors that came with the new system, it didn't work. The injectors that are mounted now are the ones from my previous system which always ran very good. So the injectors should be ok reallly. The 3.6bar was measured with car running for approx. 2minutes, it went up to 3.6 and stayed there. This should be correct according to manual.
I've been doing some more thinking, I found it a bit weird that the system didn't come with an anti-tampering CO% plug on the air flow meter. Maybe someone touched it or the screw wasn't adjusted yet when they took it out of the factory? Could it be that the mixture is set so rich (screw turned clockwise, which makes the plunger go up) that it's letting fuel through? picture: http://www.race.nangreaves.com/golf/FU01/i21961.gif CO higher -> screw clockwise -> plunger goes up -> lets more fuel through EDIT: Well, i turned the CO screw 4 full turns anti-clockwise but it didn't help...
UPDATE! I finally found the problem, It was the CO% screw! As I said, the injectors were spraying fuel with the air flow plate in its resting position. I put the injecors in glass bottles, activated the fuel pump so the injectors were spraying again. And then I turned the CO% screw anti-clockwise, after about 14 half turns the stopped spraying. Then put everything back, the car started immediately and runs on 4 cylinders. Turned the CO% screw a little more cause it was smoking at the back.
