Quote:
Originally Posted by Lar911sc
Hello! I have a cold start issue that I’d love some help diagnosing.
The car:- 1979 911 SC
- 3.0
- 72,000 Miles
- Brand new tune up – wires, plugs, rotor, distro
- Clean fresh gas
When I start the car with a cold engine it fires right up, but immediately drops RPMs and behaves as if it will stall – but so far it hasn’t stalled out. After a few seconds the RPMs rise to ~900rpm, then up to ~2000rpm a few seconds later. The car stays at this RPM range for about minute before it drops to ~1000rpm and is ready to go. Once the car is warm this problem does not occur on restart.
Video of a cold start: https://youtu.be/t4ccCql7o-8
I suspect the WUR but was hoping that maybe someone here had experienced and diagnosed a similar problem before I throw a $400 part at it.
Thanks!
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The issue could very well be the WUR, but you do not necessarily have to replace it. You do need to invest in a fuel gauge pressue set, however. You need to establish if your system, cold control, warm control, and residual pressures are in spec--assuming all else, like timing, ignition, and valve clearances are good. Your symptoms are consistent with a too high cold control pressure, but you need fuel gauges to check. If so, it is easily remedied without buying a whole new WUR.
The key to your issue is to
eliminate possibilities, of which the WUR is but
one. You need a fuel pressure gauge to verify its proper function.