K-Jet info and testing.

[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.

[RedMk2Gti]

A liitle supplement to this

Although not for VW, it contains valuable information about k-jetronic system

K-Jet.org | Mechanical Fuel Injection Power!