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911 Warm-Up Regulator Adjustability

Pelican Technical Article:

911 Warm-Up Regulator Adjustability

Bob Tindel


3 hours3 hrs






Ohm meter, 5mm Allen key, 5mm drill bit, electric drill, 1.5mm drill bit, 8mm box end wrench, brass drift

Applicable Models:

Porsche 911 (1974-83)
Porsche 912 (1965)
Porsche 930 Turbo (1976-79)

Parts Required:

5mm Allen head screw, 8mm diameter nut, washer, 1.5mm roll pin, CIS gauge

Performance Gain:

The ability to externally adjust the warm-up regulator facilitates a proper running engine

Complementary Modification:

Replace the warm-up regulator instead of just repairing it and modifying it for external adjustment

The article on making the WUR adjustable is by Jay Pineau, Ark-La-Tex Region, PCA, in Volume VII, pages 116-117 of Up-Fixin. In case you don't have that, here is the text:

An engine equipped with a Bosch CIS (K-Jetronic) fuel injection system depends on the accuracy of the control pressure for starting and driveability performance. If during a system pressure and performance test it is determined that the warm-up regulator is at fault, you are faced with an alternative: replace it (list price now about $280) or attempt to repair it.

The regulator is a fairly simple device which varies the control pressure with temperature (both engine and self-induced via an internal heating element). There are two main causes of malfunction: heating element failure and foreign material in the metering chamber.

A quick check with an ohm meter will determine if the heating element is defective. It should read 18 to 22 ohms resistance (I didn't get this exact reading, but it wasn't an open circuit). If the element is faulty, the regulator must be replaced unless you can locate a replacement heating element from a used regulator.

If satisfactory, the regulator can be carefully disassembled and cleaned. Take care that the two small orifices are completely clear. If the diaphragm shows any wear, flip it over at reassembly. (Be careful here-the diaphragm is VERY thin metal. I didn't disassemble the bi-metal spring, just pushed it aside to remove the diaphragm.)

After re-installation, it may (WILL) require readjustment to obtain correct pressure relationships. (These pressures vary with the year of the car and the part number of the WUR. You can find them in the shop manual. If you don't have them, I can Xerox and snail-mail)

Bruce Anderson described in PANORAMA (October 1984) how this adjustment can be accomplished by "knocking the plug". The only problem with this procedure is if you "knock" it in too far, you must remove and reassemble the regulator to "knock" it back (indeed true, I tried this method). By the time you have obtained the best cold and hot values, you may have to do it several times.

The unit can be modified to provide for external adjustments by the addition of a pull-out screw and nut which permits very accurate movement of the plug."

The article also includes a diagram, but essentially you drill and tap a 5mm hole about 10mm deep into the center of the plug. Then drill a second 1.5mm hole in the crack between the plug and the WUR body. Put a 1.5mm roll pin in this hole and tap it down flush with the body (the idea is to keep the plug from rotating when you move it up and down with the pull-out screw).

Put a 5mm allen-head screw, with a washer slightly larger than the plug, and a 8mm diameter nut, into the 5mm hole. Keep the nut backed off, and gently tighten the screw until it bottoms in the hole. Now, to raise the plug (higher control pressure), hold the screw with an allen key and tighten the nut (it's a tight fit, but an 8mm box-end wrench should fit over the head of the screw). To lower the plug (lower control pressure), hold the screw, back the nut off, and then tap the screw (I use a brass drift and it takes a fairly hard whack).

Of course, while you are doing any adjustments, you need to be looking at the control pressure. I bought a CIS gauge from J.C. Whitney for less than $60. Be sure that the electrical connector to the WUR is disconnected when setting cold control pressure, and that the engine is dead cold. To get the fuel pump to run, jump terminals 30 and 87a on the fuel pump relay socket (on my 83, it is the red relay in the luggage compartment).

If your car doesn't have an O2 sensor, you are completely dependent on correct fuel pressures and mixture setting to get the engine to run correctly, so the WUR is important. After I did the WUR modification, I am confident that I can set my engine up properly, and it starts and runs perfectly, cold or hot.

Bob Tindel

Comments and Suggestions:
Jose Rosa Comments: Thanks for your article,but I have question about regarding the replacement of my WUR.My car is a Porsche 1977s with a WUR 00438140061Bosch France,but I can,t find a replacement for it.Ilooked in Bosch France but they gave me another number with no indication that it is a replacement for my unit.What can I do?
February 19, 2015
  Followup from the Pelican Staff: Try a local Porsche specialist. They may know of a supplier.

Give our parts specialists a call at 1-888-280-7799 and they can help figure out which part or repair kit you need.
- Nick at Pelican Parts
sb Comments: hi, what is knocking the plug?
i have a mercedes 380SL with a ropey WUR since i took it apart to clean
June 22, 2014
  Followup from the Pelican Staff: Are you referring to the knock sensor? It is a sensor to detect engine knock. Usually mounted to the valley or engine block. - Nick at Pelican Parts  
jeal1953 Comments: Dear Mr. Tindel.
My apologies, I do not write English I am doing it for a translator of little electron of INTERNET.
My request is, A WARM's TECHNICAL DATA UP, for a vehicle Mercedes Benz, model 450 sel, year 1979
Many Thanks in advance.
I live in Venezuela
January 6, 2012
  Followup from the Pelican Staff: I'm sorry, I don't understand this at all. - Nick at Pelican Parts  
Clint Comments: I thought of this idea 25 yrs ago when we were ice racing a VW rabbit. As you say, we were "knocking the plug" to drop our control pressure for better throttle response, and once I did knock it in too far,and it was just too rich, so I had to take it apart. But I rolled the Rabbit,and the next year we moved up to a VW Golf with KE Jetronic injection, so I had a whole new system to learn,and my adjustable regulator never got built. It is always great to see your unfulfilled ideas proven valid. Thanks! Also the roll pin was a nice touch, I hadn't thought of that.
September 18, 2011
  Followup from the Pelican Staff: Thanks for the input on this one. - Nick at Pelican Parts  
MBAtarga Comments: Here's 1 of the threads on the subject which includes the picture from the Pano article Post #14 by Gunter:
February 8, 2011
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. - Nick at Pelican Parts  
January 1, 2011
  Followup from the Pelican Staff: This was answered by another respondent. - Nick at Pelican Parts  
Garth Comments: Can someone send me the exploded views of the modifications in order to get a better idea and enable me to modify my WUR
September 22, 2009
  Followup from the Pelican Staff: I think someone published these in our Tech Forums if you want to do a search there. - Wayne at Pelican Parts  
tmechanic Comments: Nice article, easily adapted to the A1 VW CIS units.
Thasnk you.
August 12, 2009
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  

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Page last updated: Sat 2/24/2018 02:21:42 AM