K-Jet info and testing.

[86gti]

OK, so I've got this issue with my valver: it struggles to start when stone cold (after sitting in the garage overnight), when it does though, it idles smoothly, no issues whatsoever until I take it on the road and occasionally (after only about a 1-2 minute drive, when still cold) it will stall (when coming to a stop/roundabout)? It's not the ISV, as I have given it a very good clean and it is working fine - again the idle is very stable.

I'm thinking it could be the cold start valve (but then after starting and idling ok for a minute or so could it stall because of a faulty CSV?) Doesn't the CSV only assist in starting a cold engine and then become irrelevant once the engine has started?

Could it be the warm-up regulator? Is there anything else that controls the amount of injected fuel during warm-up? I'm thinking the engine is not getting enough fuel when it's cold. Mind you, it runs perfectly fine when warm/hot - starts first time every time, starter motor only needs to turn once and idles very smoothly - it never stalls when warm/hot.

Where is the warm-up regulator located?

Can anyone help, please?

Cheers,
Dom

You may have already fixed the problem (sorry Ivé been offline for a while)..
I had the exact same problem with my 8v. gradually got worse. ended up being the main pump.
If it was dead cold or very hot it would stall and splutter.
Then it would only start if it was dead cold. then it wouldn't start at all.

The WUR is a very weird thing. my car had it dissconnected when I got it. and weather plugged in or not it makes no difference.
and It shouldn't cause a problem with initial starting.

I also have a problem with starting if I park nose uphill for a long time. Possibly the acumulator... not sure untill I get back to Aus.

Sorry I can't post more pics. I had tonnes of pics and info on my old computer...and the HD decided to head south.

[ozgti]

What causes a misfire/stumble at low revs then clears itself after 3k then gets worse the more you drive it ie: the misfire/stumble begins to creep up further into the rev range? I've changed the fuel pumps and still the same. Is this a sign of the metering head/sensor plate going south?

[86gti]

may even be an ignition problem? difficult to say from here. does it seem like a really big stumble like lack of fuel or a miss like lack of spark? is it starting cold ok now or still being a ^%$^^? when cold?
try bridging the relay with a switch at the relay box just to be sure it isn't the relay. might be a fulty contact that is getting worse over time from arching.

[86gti]

if not that try a flow test from here.

do it as written above, but trace this line back to the joiner near the firewall. Just a screw off fitting and fire the pums up with the switch attached at the relay housing.

[ozgti]

may even be an ignition problem? difficult to say from here. does it seem like a really big stumble like lack of fuel or a miss like lack of spark? is it starting cold ok now or still being a ^%$^^? when cold?
try bridging the relay with a switch at the relay box just to be sure it isn't the relay. might be a fulty contact that is getting worse over time from arching.

Yeah.. Like there's not enough fuel.. It sounds like a tug boat for a few revs, then comes on song but i need to feather the throttle for about 5 mins with a few big revs to get it to even run.

When cold, it will start with a bit of prompting from the loud pedal, but as soon as any load is placed, it dies.

I'm going to try a different relay if I can find one!!!

[86gti]

Just find the relay that looks like this. make up a wire with a switch in the middle and 2 spades on either end and put them into where the 2 big pins on the relay fit into the relay housing. flick it on to fire the pumps up and see if it starts ok.
If it's still being an A%% then ít wont be the relay. However it's a good idea to carry a spare in the glove box!!

you could use and modify it to use pretty much any tachometric relay, but keep in mind the relay also controls your rev limit fuel cut.

[86gti]

Sorry I have been slack in Updates. Weather is cooling down here now......so more time inside!!

OK.

Cold Start Injector

Pretty basic really. Just inriches the mixture at start up....
you will find it on the inlet manifold, usually blue in colour..(well mine is...so it may be a different colour but with a plug a bit like an EFI Injector on the harness.
It sprays fuel into the engine at systems pressure when the engine temperature is cold and the starter motor is activated. The length of time that this additional injector sprays is determined by the engine's temperature, seen by the thermo time switch.

The thermo time switch provides the earth path for the cold start injector via a heated bi-metalic strip, this heater is activated by a voltage from the starter motor. As the strip heats, over a period of approximately 8 to 10 seconds (when cranking only), the legs on the bi-metalic strip separate and the earth path is lost.
A warm engine will perhaps only require 2 seconds before the circuit is broken and a hot engine will already show open circuit. the circuit is to avoid the engine being flooded when cranking and the additional fuel is only supplied when it needs to be.

[86gti]

Auxiliary Air Valve

found along the rear of the valve cover or just to the right rear corner when looking at the engine from tha front.

umm...A thing.... to aid the engine when cold by opening a small port to increase the engine's idle speed. The fast idle control is made by the port being held open by a bi-metalic strip ( they love those strips!) that when heated by it's own heater element, or natural heat soak from the engine, the port closes. The voltage supply to the air valve is the same as the feed to the fuel pump and the warm-up-regulator.

If the idle speed will not reduce and that the speed is maintained artificially high when warm, clamp the rubber pipe between the air valve and the inlet manifold. If this causes the engine rev's to go back to normal, the fault is a buggered valve.
It is worth cleaning the valve, lubricating it and re-test it's operation. The internal heater element can also be checked for continuity using a multimeter.

[86gti]

Fuel Injectors.

To be totaly honest, I don't really know much about the injectors tho they are fairly simple in theory.
so most of this will come from my Bosch yellow jacket book.

The injectors fitted to this system will open at a predetermined pressure and will spray a fine atomised 'mist' of fuel behind the inlet valve, waiting to be drawn in on the induction stroke. The fuel is delivered into the engine in a continuous spray and is not timed or pulsed as on other systems. The opening pressure of the injector is at approximately 3.3 bar at which point fuel is injected into the manifold; when the injector pintle opens this will cause the pressure to drop, subsequently closing the injector, which causes the pressure to rise once again and this will of course open the injector. This pintle vibration is called 'chatter' and helps to atomise the fuel before it's induction.
When the engine is switched off the fuel pressure drops below 3.3 bar and the injector closes forming a fuel tight seal, helping to avoid fuel dripping into the inlet manifold.

The spray pattern should be a conical shape and when clean and working efficiently, should emit a high frequency noise: this is the sound of the pintle 'chatter'.

[86gti]

Basicly here is some trouble shooting info for differing problems.
Pretty much General areas of where to look for certain problems.

K-Jetronic: Troubleshooting Symptoms


MAIN Symptoms with the system.............................

Engine does not start/starts hard when cold.

Engine does not start/starts hard when warm

Irregular idle during warm-up

Irregular idle with warm engine

Engine will not accelerate, backfires,

Engine backfires under load.

Poor Performance.

Engine runs onFuel consumption too high.

Driving performance unsatisfactory

CO concentration at idle too high

CO concentration at idle too low

Idle speed cannot be adjusted (too high)

Engine starts but immediately dies.
----------------------------------------------------------------------------------



Symptom: Engine does not start/starts hard when cold

Remedy
Sensor plate and/or plunger not moving freely Check for free movement*
Auxiliary air valve does not open Check valve for correct function*
Electric fuel pump not operating Check pump fuse, pump relay and pump*
Cold start system defective Check cold start system*
Therm-time switch defective.... Test thermo-time switch*
"Cold" control pressure outside tolerance Test pressure*
Injector leaking, opening pressure low Check injectors on tester*
Injected fuel quantities unequal Check for equal fuel quantities*
Basic idle setting incorrect Check and adjust CO level*
---------------------------------------------------------------------------------------------------
more soon.