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Post mortem on valve disaster (See photos in gallery) Posted by TonyJ [Email]  (#407)  [Profile/Gallery]
(more from TonyJ) on Fri, 4 Nov 2005 18:08:42
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Well, I bought a used fuel rail banjo bolt from Sobstory as someone suggested, then built an adapter so I could measure fuel rail pressure. I taped a gauge to the windshield just beyond wiper range and went driving up steep hills on highway 2 west of Fitchburg. Pressures ranged from 34 psi to almost 60, uphill with boost in the red. Then I did a pressure test at various regulator vacuum/pressures per the Saab manual and it passed with flying colors. It had also passed the fuel delivery test. Results from injector blueprinting are that some were a bit off before cleaning, but not enough to cause such a disaster, according to Marren Fuel Injection service.
So what was the problem? There appear to be two possibilities left
1. It appears to be running a little lean, with white plug insulators and
exhaust valves in the good cylinders (see my photo gallery). But some mechanics say the old rule about light tan being best doesn't hold these days, with unleaded fuel, etc. ANY THOUGHTS OUT THERE??. Is there a sensor failure that would make it lean without generating codes?
2. The last time the car was gassed was with 93 octane (which I always use in both Turbo Saabs), but at a bargain price (relative these days) Unified Petroleum station and several mechanics have suggested bad or underoctane fuel as a possible culprit or major contributing factor. I still have the fuel from the flow test, but have been advised that octane testing is very expensive. Given the sophisticated TRIONIC system, how could a fuel issue have caused this problem anyhow?
The other exhaust valve in the affected cylinder looks OK, so I think it was just a combination of heavy load, high speed, cool temperatures that enable high boost, a damaged or defective valve (as suggested by SWEDECAR), and a long uphill pull with trailer in tow.
I really want to understand what happened so it doesn't recur. Any other thoughts??
, Fri, 4 Nov 2005 18:08:42 <-- Viewing This Message, Mon, 7 Nov 2005 21:01:23
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