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Warm up regulator adjustment

G

Gibbo

New member
Hi, I posted a problem a while back regards a stutter/miss around 1800 to 2500 rpm, on my 79 sc, after much head scratching and changing all the cheaper bits(relatively speaking) it was isolated to the WUR, I bought one off ebay that had been modified with a screw to allow adjustment when in situ, I fitted it and as soon as full of fuel it started first time and when warm runs perfectly, problem gone..the only issue is that when cold it hunts a little, I want to adjust it but looking at threads and articles I'm a little confused. Does adjustment of the WUR only affect the cold running, or will adjusting it affect hot running also, as said I have read conflicting views, any advice will much appreciated..... love to porkers everywhere Tony

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From memory there is basically a bi-mettalic arm that alters spring pressure on a spring loaded diaphram. I would guess the screw is altering the amount of pressure placed on the diaphram in some way, or on the arm, to adjust the fuel flow. The warm up regulator should only be operative during the warm up cycle and should have no effect after. To adjust your screw i would guess you would need to know optimum fuel pressure or rate of flow when cold and adjust it accordingly. So you need a fuel pressure gauge and hose, capable of reading system pressure 100psi on CIS. Or it may be adjusted by flow rate(run fuel pump with open line after WUR into a container and measure amount over time ) but i can't recall. There are quite a few useful websites out there that cover Bosch CIS well and a couple of good books too.
Hope this helps a little.

P.S> hunting idle on a SC when cold is entirely normal and how they worked from new !
 
Well at the moment,I have one in bits from the 924 with points ignition,that I have been trying to get started for several months.Having rebuilt the fuel distributor,checked all injectors,extra air valve,cold start injector,I am now working on the rest of the fuel system starting with the WUR back to the tank.
From the photo above ,the adjusting screw appears to have replaced the internally fitted brass stud onto which the steel spring actuator arm,which has the electric heating coil on it, fastens against a fixed location with a brass nut ,washer & lock washer.
I presume that by being able to alter this fixed stop position,either way,alters the loading of the spring against the conical cup on which it bears,& therefore alters the loading of the pin located in the coned cup on the thin stainless diaphragm on which the other end of the pin is located.
When cold ,the diaphragm closes as far as I can trace & no fuel can flow back to the fuel tank,thus maintaining higher pressure in the system-as the housing warms up with engine heat from the manifold & from the heating coil,the return valve opens progressively altering the pressure as fuel starts to return to the tank,so I presume the adjuster must change the point ie temperature when this happens.

That's my understanding so far (& am happy to be corrected as I haven't tried to dismantle the steel valve which seems to be clamped by it's 4 screws through the aluminium housing of the WUR).Since no fuel goes into the housing but purely circulates in the steel valve,I am not sure quite what actuates the valve,other than differential pressure as under the SS diaphragm disc is an O-ring around a shallow recess in which there is a small hole through to the outside return fuel tapping (I have blown through this with compressed air & it only emerges at the one tapping)

When I have summoned up the courage to attempt to dissemble the valve (it's not my car!),then maybe I might be better informed.)
However,I would agree with Lawrence that a pressure gauge could be necessary so that hot running pressure is correct & not affected by overdoing the adjustment.
 
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