Bosch K-Jetronic fault finding

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A3@MBB

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Anyone on the forum that have knowledge on these systems? or can direct to someone knowledgeable on the topic?

Short version -
Jetta mk2 Cli idled away and presumably cut out because of low fuel. No known faults prior to this or any hard starting problems.
Added 5l fuel and tried starting again later in the evening (cold engine), but only swings.
Fast forward to last weekend, changed the fuel filter (outside canister) and checked for fuel pressure at the distribution point on the FI- all checks out.
Motor swings and starts briefly with no throttle applied and dies.
With throttle it dies instantly.
Where to from here?
 
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Have you tried the VWCSA forum? There aren't many left who have worked on K-Jet, let alone know what it is, where are you based?
 
To be honest i did not trawl through the local forums, but UK's and a quick google or two.
Car is in storage in Stilbaai - which makes it a bit more difficult
 
Car did run and idled stable up until the point.
I hazard a guess that a air valve is stuck in open position or something similar.
 
Have you checked the spark plugs at all? Firstly to make sure there is good spark at each cylinder and secondly to make sure they are not fowled up.
 
Symptom: Engine does not start/starts hard when cold

Cause
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

It can only be the 4 in red above, how do I test these?
 
And here was I thinking fuel injector systems are easy to work with, looks like VW has found a way to make it complicated.

I think the auxiliary air valve should be the idle control valve, I am totally clueless on VWs so I could be wrong, if it is then it should be easy enough to remove it and see if the valve moves when the car is turned on, give it a good clean with a carburetor spray either way.

I honestly have no idea what a cold start system is but I think it could be a combination of sensors, air sensor, coolant temp sensor etc.
 
Remove the electrical plug from the Cold Start injector (A on the picture) after it had stalled after starting. Then start it with fully depressed accelerator, it may take some time to start as the engine might be over fuelled.

Switch off and start again, if it starts immediately and idles normally it might be that the cold start temperature sensor (B in the picture) might be defective and keeps adding excessive fuel through the cold start injector while not required after the initial starting sequence.

Alternatively you can also remove the plug on B temp sensor to do the same test.

Try this, it might be something different.

1650461499979.png

This was my trusty Jetta engine after about 200k Km.
 
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Stokstert said:
Remove the electrical plug from the Cold Start injector (A on the picture) after it had stalled after starting. Then start it with fully depressed accelerator, it may take some time to start as the engine might be over fuelled.

Switch off and start again, if it starts immediately and idles normally it might be that the cold start temperature sensor (B in the picture) might be defective and keeps adding excessive fuel through the cold start injector while not required after the initial starting sequence.

Alternatively you can also remove the plug on B temp sensor to do the same test.

Try this, it might be something different.

View attachment 1295242

This was my trusty Jetta engine after about 200k Km.
Click to expand...
Thanks, I will follow the instructions as soon as Im at the vehicle again.
 
Stokstert said:
Remove the electrical plug from the Cold Start injector (A on the picture) after it had stalled after starting. Then start it with fully depressed accelerator, it may take some time to start as the engine might be over fuelled.

Switch off and start again, if it starts immediately and idles normally it might be that the cold start temperature sensor (B in the picture) might be defective and keeps adding excessive fuel through the cold start injector while not required after the initial starting sequence.

Alternatively you can also remove the plug on B temp sensor to do the same test.

Try this, it might be something different.

View attachment 1295242

This was my trusty Jetta engine after about 200k Km.
Click to expand...
That's beautiful, what happened to it?
 
The fuel inject system very seldom goes wrong on those cars.
Check the coil pack for good spark.
Injectors??? Dripping or broken.
Alarm system kicking in?
 
Not sure if not clear in OP, but the car had no trouble with the FI (limping / rough idle / hesitation on acceleration) or spark before. I think it ran out of fuel.

Standard Alarm system - I did not test to bypass the engine cut with the key, thanks for reminding me @Thugscub
 
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