A few K-jet running issues

I've been trying to troubleshoot my cold start issues with my newish 1989 16v GTI, what with all the time off!

I followed a few guides today to see if I can narrow down my issues - one said to disconnect the blue switch/plug from the fifth injector to see if it helped the cold start issue - well it seems it does. Obviously there are only so many times you can start from cold before you have to wait again till the next day, so with it currently disconnected, I am going to try again tomorrow morning and see it starts with no problems.

My symptoms are: Nearly always after the first turn over, it will catch and then die straight away. The second time, it will either turn over for ages and then catch, or not catch at all. To remedy this, I have taken to (the second time I turn over), holding my foot to the floor to force some air through, my reasoning is it is possibly flooded as it can have quite a pungent over fuelling smell. - After it finally catches and fires up, it hunts like a mad b*stard and is erratic for the first 30 secs to a minute, gradually getting better until the idle is *almost* perfect.

I've changed all vacuum hoses/pipes and checked for splits etc. Today I also followed the 2% CO guide, using a long 3mm allen key and got the idle running pretty decently. Took it out for a spin, seemed very responsive (all the time with the 5th injector disconnected) One major issue I had, which I think might be responsible for the hunting, was that when trying to adjust the idle mixture, if I applied even the smallest amount of pressure on the idle mixture screw the engine started to majorly bog down and if I pressed for more than a second or 2 it would die. Could there be some fault in this area that is attributed to the cold start issues? I'm guessing you should be able to adjust the idle mixture without the engine cutting out (note: I wasnt even adjusting at this point, just getting the allen key onto the screw)

Where should I go next?

 

K-Jet is all about fuel fuel pressure...


Get yourself a set of fuel gauges with shut off valve and check system is making pressure then holding residual
pressure after sitting.

Also check overrun cut-off valve (remove and clean) quick system check would hold revs @ 2500 and push throttle switch in
revs with dip and you will hear the valve working

Get timing set then Co with a proper metre and remember to disconnect the plug at the coil.

Better still take it to someone that knows what they are doing

 

Pressing on the idle mixture adjustment screw will move the airflow meter plate, and lean out the mixture briefly, causing the problem you describe:



Just try to be as gentle as you can, and make a small adjustment each time. Try 1/4 turns at a time, and make note, as then you can always return to where you started if it runs worse. Remember to remove the tool after each small adjustment, and give the throttle a small blip to settle the pivot into position. If you haven't access to an idle CO meter, you're aiming for a good smooth idle, without misses. Idle speed would then be adjusted back down using the idle screw on the throttle body (on an 8v, sorry not sure how your idle is governed).

As far as the cold start valve goes, it's worth checking it doesn't drip with the engine running I suppose, but ultimately it's controlled by the thermo-time switch, and if this is not functioning correctly it would give the symptoms you describe. There is a test in one of the hayneses, but the full guide from Bosch can be downloaded from scribd.com. Mine's gone also, same symptoms as yours so I only connect it during midwinter.

 

How is the rubber intake air duct and bellows? Crack free?

 

Cheers for the replies so far guys - car starts on the button now since disconnecting the cold start valve/5th injector/blue connector - also I've noticed far less white vapour/smoke upon start up and when it's cold, and the smell of fuel is far, far less. Would a good guess be unburnt fuel coming out of the exhaust? I'm going to leave this disconnected for now, not quite sure why it is there if the car starts perfectly without it? It was about 6 degrees this morning on start up, so certainly classed as cold, but it fired up fine!

There are no holes or splits in the intake rubber boots, I replaced one of these very recently because of that problem, the rest are in perfect condition.

With regards to fuel pressure gauge, is there a cheap kit I can get off of ebay? Not really sure what I'm looking for..

 

When first starting in the morning try turning the ignition on and off a few times (4 to 5)
this will build system pressure, you should hear the pump each time.
Then try to start if this sorts/helps, your problem will be your accumulator not holding residual pressure or the non return valve on the end of your fuel pump has failed.


cyber fixing/answering is a b i t c h
sorry can't be of more help

 

Cheers John, that has sort of confirmed the conclusion I was coming to (which is why I PM'd you about those injector part numbers! )

It is indeed perfect when starting from warm and in all other situations, just stinks of fuel and is bogged down on a cold start, it hunts and fluctuates and generally sounds sh*t until a few minutes have passed. It's currently at a local garage having a few exhaust blows looked at which can't do it any harm I suppose, might give me back a few runaway horses!

I'll see if I can get some injectors cheap, or maybe get mine refurbed/cleaned and go from there!

 

accumulator and non-return valve only effect warm starting really

accumulator starting to fail will mean you have no pressure to open the injectors in the morning on first start never came across to many problems with K jet injectors leaking
overnight, even at that sensor plate would be down-no air to lift it as engines not running = no fuel to injectors.

Tell you what
If you think a set of 16v injectors will sort I should have a good set in my box I would sell 25 to your door
but can't see it fixing it.

Better still
Run it for a bit-stop it then pull the injectors out/wee pull and place in four gassses.
This will tell you if they are leaking

 

Cheers for the offer Volksport, I may take you up on that offer - will have a look at my injectors first and see if I need them!

John, those injectors would definitely have been a bargain, I sent him a message a couple of days ago asking him if they are working correctly, the right spray pattern etc and a price and ETA for delivery to the UK (it specified worldwide delivery in advert) and had no reply. Tried to contact him tonight but it came up with unfortunately the seller cannot answer your question, or something along those lines, so thought for the price, I may as well buy them, so went to click buy it now and the seller has added me to a ban list! I couldnt bloody believe it, what a ******. I've never been ban listed, had any negative feedback or issues with buyers or sellers and he ban lists me. The only thing I can think of is he didnt want to post to the UK, or have the courtesy to tell me so, so he just bans me. Cretin. I couldnt send him a message via the item itself, so I had to search for his name in the ebay seller search section, after which I sent him a not so nice email, telling him what a knob he really is!

 

If your going to copy and paste, put the lot up

15.1.5 The Accumulator
The accumulator is the first of the components in the fuel system after the pump. This unit has an important role to fill in the operation of the Bosch K Jetronic system.
Its first job is to help smooth out any pulses in the flow of the fuel, this is achieved by passing the fuel through a series of baffles and into a chamber giving it slight capacitance and a much smother flow. Its other and possibly more important role is to maintain pressure within the system when the fuel pump has been switched off; this is achieved by the accumulator spring and diaphragm pushing against the fuel.
For the duration that the engine is running, the diaphragm will be against its stop within the spring's chamber. When the engine is stopped and all of the non-return valves close, the spring pressure against the diaphragm will maintain the residual or holding pressure and overcome any slight seepage.
Within the data books for this system, it is shown that the critical time for maintaining these pressures, is between 5 and 20 minutes. After a journey, when the engine is switched off, the under bonnet temperature increases causing the fuel in the lines to heat and it attempts to evaporate.
Maintaining the pressure eliminates this problem and ensures a clean start when the vehicle has been standing with a hot engine.


"You've never used a set of k-jet pressure gauges before I take it "

Yes jonny you would know


As I said at the start get a set of gauges and go through it
before you start buying changing injectors etc



As I said lets see what fixes it.

 

Could any of the previous owners have fiddled with the WUR at all? Could be worth just unscrewing it from the head to see if the brass cover for the adjustment screw has been tampered with, or is still intact..

Low control pressure would lead to an over-rich mixture everywhere, but during the warm-up enrichment phase it would have more of an effect.

If it has been diddled with you will need a pressure gauge to set it properly though.

 

Totally agree on the cold start injector, as unplugging it has made a difference.

However, the 30-60s of hunting after starting would suggest there could also be a prob with the warm-up enrichment. Perhaps resulting from a previous owner trying to solve/bodge this same problem before, perhaps not. A quick peek at the rear of the WUR would confirm or deny this.

Either way it could need adjusting, but I'd be getting the idle CO checked professionally, before splashing out on pressure gauges, just in case. I'm assuming the ignition timing is all spot on?

 

My 5th injector has been disconnected for many years & the car has always started with no issues however cold it is.

Makes me wonder why it was ever fitted?

 

For what it's worth, I don't even bother connecting my CSV until it gets below -15C. Starts fine without it above that.

Only reason I disconnect it is 'cos the thermo-time switch isn't right. Certainly not going to buy another at 150-odd quid each new!