jumpinjimmy

I bought the pressure test kit from Pelican to try and diagnose what's wrong with my 1983 911sc, which seems to run rough when cold and doesn't idle well when warm. The cold test showed a pressure of 1.2 Bar and the warm test showed 2.5 bar and it was very slow to climb up to the 2.5. Does this mean I should have the WUR serviced?

theiceman

which pressure are you talking about
system pressure or cold control pressure ?

the first thing you should check i system pressure , this verifies your fuel puump is putting out enough pressure.

If that is good control pressure is dependant on ambient temp. Also you need to make sure you have the right WUR. check the part number on it vs what it is supposed to be.

jumpinjimmy

I should have mentioned that prior to this line pressure test, I installed a new fuel pump, fuel filter and fuel accumulator. I don't have any reference for what the right WUR should be. Is there a list to compare to?

jumpinjimmy

Also, it is really cold out at the moment, around 6 centigrade...can that influence test results???

theiceman

You really need to get a Bently , the system pressure is the system pressure , that will have not fluctuate with temp .

The Control pressure definitely will fluctuate with temp.

The Bently manual has a graph which shows the profile of each WUR, and how it should read based on ambient temp. I would post a pic of the manual here but i think its a violation of the copyright policy.

jumpinjimmy

ok, not sure about the terminology here but I believe I am checking the control pressure. Cold being tested with engine cold and electric terminal disconnected from WUR. Warm being tested with terminal re-connected. Jumping the electric contacts 87a and 30 off the relay block. Not sure if system pressure is relevant or not in my case.

jumpinjimmy

also, just did a quick check on google and can't find how to check system pressure.

jumpinjimmy

No other thoughts on this? Kind out in the sticks in rural France with no other resource unless anyone can recommend another forum that might be more technical minded.

psychoideas

Search google for bosch k jetronic CIS pdf.
There a a few porsche related PDFs free to download that have the correct sequence of testing with a pressure gauge.

jumpinjimmy

Thanks, yes, I have done that, and it would seem to indicate that my WUR is defective. I'm just hoping for some confirmation before going to the expense of having it repaired.

psychoideas

I pulled mine apart and adjusted and cleaned it.
There was a mesh screen in mine that seemed to be blocked by a type of lacquer maybe carried by the fuel. I put acetone on it for several days and brushed it with a very small stiff brush. I did this several times. They are adjustable by forcing the bi metal mounting stud either up or down. I tapped mine in or out with a hammer and re measured it after each tap.
Anyway, I got it all working within tolerance and to spec.

jumpinjimmy

I'm going to remove it this morning and have a look over it.

theiceman

you should go to pelican-parts website . it is very technical for air cooled and have a thread called cis for dummies it is very good and will get you going.

you need a thorough understanding before trouble hooting including how the frequency valve works.

psychoideas

That one escapes my memory. Is that near some sort of capacitor?

theiceman

exactly .. its next to the FLUX capacitor .. but only on 80 and up cars so we are safe ..