Tutorial: Bosch K Jetronic Warmup Regulator / Control Pressure Regulator - how to check & adjust

Tutorial of the internal function of the Bi-Metal and the effects of aging and metal fatigue and which ways the Bi-Metal can be adjusted to restore proper fuel pressure for cold start and hot start. Hot ONLY if engine is shut off when warm and then restarted within 2 minutes. That’s about how long it should take for the Bi-Metal to cool down and go back to its “cold” position.
You can check this by removing 12V from regulator after you have reached maximum pressure. The pressure should drop off within 2 minutes to the required cold pressure for your car.
I will make another Tutorial on how the WuR / CPR actually regulates the mixture at a cold start and a warm start with the associated vacuum temperature switches and check valves, how the Bi-Metal fits into this picture and which will probably explain why it is called a Warm Up Regulator
Thank you Cabby-info for the animated gif image

[@Blutnase]

This is the best explanation of the WUR on KZbin. Thank you sir.

[@austinanderson7855]

You are amazing. This is a beautifully explicit video. Very, very well done, sir

[@richthekid1872]

I'm always excited for a video of yours . I look up to your work and hope to one day be as knowledgeable as you sir. I also aspire to learn these systems and help others with a passion . I thank you for giving someone like me a vision and dream . To one day be a good technician such as yourself that helps others I own a w126 and I got into this through seeing your videos .

[@ImpalamansGarage]

Excellent and in depth as always!

[@inovahightechltd]

Thanks Mike!

[@foxlair3682]

Fantastic! Thank you.

[@natejgreene9871]

Ive heard that adjusting the wur screw can have a big impact on fuel consumption if it's not set exactly right. That is why i was always hesitant to mess with mine. I eventually just paid CIS Flowtech in Alabama to rebuild and calibrate mine. they do very good work.

[@Zhagg1]

Excellent!

[@scanhead177]

Could you recommend a pressure testing kit? I have an 85 golf gti 8v that's cutting out when cold and a 16v that's cutting out when warm. Both have been sitting for a few years and I think testing the WUR is were ill start. I'm in NZ and I think our fuel might not be the best for these cars.

[@inovahightechltd]

I bought one from tooldiscounter.com for like 90 bucks almost 3 years ago. It has held up ok for the 3 to 5 times I used it on two different MB’s. My 89 560 and my friends 1980 450SEL It is not the best quality but hasn’t started to leak either. It has the switch valve similar to the original MB/Bosch unit. I verified the accuracy of the pressure gauge before each use. The accuracy has remained steady. This is a universal gauge for all K and KE Jetronic’s www.tooldiscounter.com/product/s-and-g-tool-aid-cis-k-jetronic-tester-sag33800?originalQuery=SAG33800

[@bikeman123]

So many cars used k-jet, many still on the road but you cant find anyone in the UK who really understands them these days. I'm seriously thinking of selling my 230E because of this.

[@inovahightechltd]

Hi bikeman123, bring your 230E to a Bosch Car Service Center. They can fix your Jetronic related issues. A good source to find Jetronic parts is Bosch Classic Website www.bosch-classic.com/de/en Peter

[@bikeman123]

@@inovahightechltd Thanks but there are no Bosch Classic Service Centres in the UK. Obviously without finding a knowledgable techinician it would be very expensive to change these parts.

[@inovahightechltd]

You will have to ship everything to Bosch in Germany

[@dnbdirector]

@@inovahightechltd don't sell your car. Better convert to EFI injection and enjoy your ride again:)

[@arhimond7]

Hello, my regulator on the M116 380 shows 3.4 bar when cold, I supply 12 volts, it rises to 4.1, it turns out a lot. How to fix it?

[@inovahightechltd]

There are videos from Kent Bergsma / Mercedessource where he shows on how to adjust pressure

[@plymouths1]

interesting video, if the warmup regulator was faulty, could you have a situation where the cold start works fine, but hot start after sitting awhile is difficult ?

[@inovahightechltd]

Yes, but the other causes for that is bad / cheap gasoline (according to Bosch ) which results in vapor locking and vacuum leaks. As to vapor locking, check if your car has a check valve installed on the fuel pump ( these were field retrofitted as recall ) and that your accumulator is working. Do fuel a pressure test to make sure the fuel pressure remains at the in the service manual specified pressure when you turn off the engine for 30 to 40 minutes. If the pressure drops fast then you may have a fuel leak, bad accumulator or a bad WuR Peter

[@plymouths1]

@@inovahightechltd Thank you Peter

[@mikemike-rf7qb]

Help..my 924 turbo has an erratic idle and as soon as I give it gas it backfires and stalls...Anyone?

[@ryanhettema8361]

Have you checked your ignitiontiming?

[@sas8403]

how is the warm control pressure adjusted, if cold control pressure is increased will the warm control pressure also increase

[@inovahightechltd]

Depends if you have the unit with double or single vacuum chamber. What is the Bosch number on your WuR? They made 132 different versions of it.

[@inovahightechltd]

Something is wrong with KZbin.

[@sas8403]

@@inovahightechltd i see my message has gone again

[@inovahightechltd]

@@sas8403 what is that in bar? What is your system pressure, 20c pressure range and operating pressure range?

[@sas8403]

@@inovahightechltd system pressure is 6.34 bar, manual allows 6.1 to 6.8 bar for this bosch regulator. At 15.5c my COLD control pressure was 2.7 bar, manual allows a range of 2.55bar to 2.9 bar. Warm control pressure was 3.9 bar, manual allows for 4.5bar,,its this warm control pressure that is currently out of spec and i need to increase

[@ace7821]

You can adjust the nut under the copper plate. You have to take apart the regulator. Others drill into the copper. This video is not really that clear in terms of function and mechanics of how this system works. Can you re do this video please?

[@inovahightechltd]

It depends on which one of the 101 different Warmup Regulators you got from Bosch. This is a tutorial for 068 WuR. Please specify your model and I will see if I can make video for your model