Cold Start Problems

[hbf]

My '73 911T CIS does not want to start from cold.

Everything checks out except for the cold control pressure. That measurement is the same cold or hot 2.9 kp/cm or 42 psi.

My diagnosis is that the WUR is not working. But here is what puzzles me: it would seem to me that if the WUR fails it should produce hot starting problems. In other words, its natural position is open (thus reducing the control pressure). Why then would it fail in the closed position? Is this possible? Any ideas.

The factory manual says at pg 2.2 - 1/16 that the WUR replacement is furnished with the plastic fuel line attached. Is this in fact so? Can anyone confirm? If not, then what is the procedure for replacing the plastic line and can these tubes be bought from Pelican? Also, if the WUR comes with the fuel line, does it also come with the banjo for the fuel distributor end?

Any guidance will be greatly appreciated.

[yelcab1]

The wur is dead, and not regulating during cold starting. Gas pressure is too high on the control side, letting the diaphram open too little and letting less gas in. Engine is running too lean to start.

[Paulporsche]

When the WURs fail or go out of spec, they seem to always lose their ability to reduce the control pressure, which is why there is so much talk of "knocking the plug" on the K-jet cars.

For parts info check out the new parts catalog or tech info sections of this website, which has expanded views of various component systems. Or contact our host.

If you search you will see info on adjusting WURs (which I think is the same for all CIS years). Using a pressure gauge will tell you if you are within spec, but I think your diagnosis is correct. If you try knocking the plug (which I think works even on a 73) you may put it back into spec. If not, and it was already beyond repair, then so what?

Maybe someone else w/ more knowledge of this vintage will chime in if there is a difference for the early CIS versions.

Good luck.