Bosch K-Jetronic System Questions Thread

[DeloreanJoshQ]

How do you test the warm up regulator? I am noticing during cold starts early in the morning the car has a slight miss at idle but once it warms up it is fine. Also, hot and warm starts are fine and it runs great at any temperature; it's just the cold miss at idle....


Thanks!

[elfking]

I managed to adjust my CO into good enough spec to pass smog and seems to run great from others here on the board. I just had to find a Multi-Meter which measured Duty Cycle...

http://dmctalk.org/showthread.php?48...-swapped/page2

Borrowing a multimeter that had the option was the hardest part...

[DMCMW Dave]

How do you test the warm up regulator?
Thanks!

With a KJet test fuel pressure meter. It's in the manual. You can buy the meter from places that sell BMW parts. (bavarian auto for one). I'm sure Dave B has one.

[Farrar]

Disconnect the wiring from the control pressure regulator. Connect a voltmeter across the electrical connectors and operate the starter briefly -- there should be a minimum of 11.5 volts. Connect an ohmmeter across the regulator heater element terminals -- the resistance should be between 16 and 22 ohms.

Farrar

[DMCMW Dave]

.......the resistance should be between 16 and 22 ohms.

Farrar

That tells you if the heater works, which is not particularly important (if the heater completely fails the car will run slightly rich for maybe 5-10 minutes longer than it would if the heater was there, depending on ambient).

It does not tell you if the regulator itself is running at the wrong pressure, which is the more common problem. You can really only see that with pressure gauges.

[Farrar]

I figured he just wanted to know if it was alive or dead.

Farrar

[DeloreanJoshQ]

Must the warm-up regulator be tested when completely cold or can it be tested at any engine temperature? (I have to drive 25 min to Dave Bauerle's shop to use the tester)

Thanks for all of the help!

[Bitsyncmaster]

Must the warm-up regulator be tested when completely cold or can it be tested at any engine temperature? (I have to drive 25 min to Dave Bauerle's shop to use the tester)

Thanks for all of the help!

When the engine is cold the control pressure reads about 20 to 25 PSI and starts moving higher within a few seconds of running. After 2 or 3 min. control pressure settles out about 50 PSI. That low control pressure is what makes the cold engine run rich. If your warmed up mixture setting is not properly adjusted to run the FV about 30 % duty cycle that setting can make the cold (before closed loop) run to rich or to lean.

So first thing would be check the mixture warmed up via a dwell or duty cycle reading of the FV. Then if you still have the problem you need to verify your control pressure as the engine warms up.

Have you checked the filter screen on the WUR yet?

[DMCMW Dave]

To really test the warm-up function it needs to be overnight cold. As (other) Dave mentioned it goes through the warm-up phase pretty quickly, and once the thermal switch has cut off the vacuum the throttle enrichment is done too.

Typically a bad WUR does not cause a cold miss, more often a huge fall-on-your face bog until the car warms up. (it feels a car with a carb missing the accelerator pump). I think you are probably chasing the wrong ghost on this one.

[DeloreanJoshQ]

To really test the warm-up function it needs to be overnight cold. As (other) Dave mentioned it goes through the warm-up phase pretty quickly, and once the thermal switch has cut off the vacuum the throttle enrichment is done too.

Typically a bad WUR does not cause a cold miss, more often a huge fall-on-your face bog until the car warms up. (it feels a car with a carb missing the accelerator pump). I think you are probably chasing the wrong ghost on this one.

Where should I start looking to find the problem?