Warm Up Regulator (WUR) questions: (1982 - 308)

I am working on the WUR (rebuilt by me, new o-ring) and the static control pressure (engine off, fuel pump on) is about 40 psi. The manual calls for about 30 psi cold (ambinent temp = ~66 DEg F). I think the WUR is not set right.

Does this control pressure value (30 psi cold) only apply if the engine is running, or is it the same running or not running ? I find that if the engine is not running, but the fuel pump is on, the static control pressure drops slightly if I press down on the airflow plate and the injectors start squirting. The static control pressure drops a bit, but not a lot.

I tried adjust the regulator plug, and the bimetallic strip post of the WUR, and still could not get the static control pressure below 40 psi. I then removed all the "guts" from the WUR so that it was just the diaphragm and nothing else (no mechanism pressing on the diaphragm) and still the pressure would not go below 40 psi.

So: if the intrinsic regulator pressure of the WUR is presently 40 psi cold (at 66 Deg F) is this a correct value, or do I have to mess with shims and/or new o-rings to tweak the regulator until it runs at 30 psi cold ?

(I am just a few days away from converting to the Holley EFI is this Bosch system does not start cooperating !! )

thanks

Andy

 

I have learned a lot about the WUR in the last 2 days.

I took it apart and figured out what's wrong with it. More to follow.

 

After working on the WUR non-stop for several days, I think I have figured it out.

I got lucky, the inside of my WUR was very clean, like new. Only the O ring under the diaphragm was wasted, all else was like new.

I dropped in a new o-ring, reassembled the WUR and found it ran 10 psi too high at cold, and 10 psi too low at hot.

So I took it apart again and did a lot of trying differnt things. I figured out the o ring was a tiny bit too thin, allowing the diaphragm to run too close to the orfice. I put a .003 alum. shim (beer can metal) between the diaphragm and the seat, and the pressure was right on.

Bottom line: If you have a bad WUR, and you are a very patient and creative tinkerer who can read and follow directions, you can do it. I did a few google searchs on "Bosch WUR" and found about 5 or 6 articles, mostly from Porsche and Mercedes web sites, on how to deal with the WUR.

After reading all the articles twice, and trying a few things, I got it back to where it should be.

If you have specific questions, let me know.

Andy

 

I think a WUR from just about any other K jet car would work as long as the fittings matched, the parameters are the same for all K jet cars, that is fuel pressure, working temps, etc. You might have to replace the diaphragm o-ring and body o-ring, but those only have to match by size. You would maybe have to adjust the cold and hot control pressure, that requires reading the articles on the WUR and doing a lot of tinkering.

Or, google warm up regulator rebuild and find someone who will do it for a reasonable price. There is a huge variation in price for that part from various vendors.

I matched the o-ring by size at the hardware store, not a perfect fit, but close enough. In the process I learned how the thing actually works.

I am not aware of any source for WUR or fuel distributor parts, other than prowling the usual junk yards. The WUR is a rather durable part, and the local junkyard was reccomended as a source for WUR and K Jet parts.

There are mail order web sites that cater to vintage porsche, volvo, etc that sell some K jet parts, but rebuild parts for the WUR is not among the parts I have seen. Mostly it's injectors, hoses, copper washers, banjo fittings, and banjo bolts.

K-jet can be found on millions of cars, rabbits, jettas, audis, volvos, saabs, benz, porsche, etc. Just about any european car from the 1980s probably has a K Jet on it. (albeit mostly 4 cyl). Most parts are interchangable.