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Thanks for the reply, Dave. Here's some additional info. Taking your points slightly out of order:
The failed fuel pressure regulator was the first problem, and quite effectively disabled the car -- the engine just wouldn't start. Diagnosis was pretty easy: the fuel pressure had pushed the vacuum line off the regulator. Replacement required removing the fuel pressure rail including injectors. I'm pretty careful: nothing fell into the injector holes while the injectors were out. I vacuumed the injector holes and throttle body (while holding throttle open) to remove any dirt that might have fallen in, but I had brushed and vacuumed the injector seal areas before removal. After replacing all parts there were no pieces left over and no missing tools. I had not yet removed the plugs before restarting the car.
Restarting the engine was difficult and the metallic noise was present when it first caught. I doubt therefore that an errant piece or my actions caused the noise. I could, of course, be wrong -- and I am gonna find out.
After starting the engine and hearing the noise, I turned the engine off and called my Volvo tech buddy. He suggested checking the spark plugs, replacing the oil, and checking the timing belt. Plugs were dirty but undamaged, timing is dead on, and the oil smelled a bit but was the proper volume. I replaced the oil filter (always do when I change the oil) and added the correct quantity of oil (20-50 synthetic blend: summers are hot out here). Engine ran better but noise remains.
Volvo tech buddy says probable bent valve. Advises against compression test or leak-down test for same reason you give: every tap does more damage. Suggests removing head for a look-see. I started doing this today.
I do have the '94 850 Volvo service manual for the car (sections 2(20-22, 25-26), with service bulletins current to about 9 months ago. I will ask the service manager of my local dealer whether Volvo has released any service bulletins for that car that I don't already have. I have read through the cylinder head section (and most of the rest of the manual, too).
The only special tools required to remove/replace the head seem to be for replacing the front cam shaft seals. My Volvo tech buddy recommended that I not remove the cam gears until after the head is reassembled, when cam friction will help immobilize the cam. At that point, he advises marking the cam gear position very carefully, removing the gear, replacing the front cam seal, and then replacing the gear in the same rotational position. I have no opinion yet on how feasible this is. I'd value your opinion on this.
I hope to have the head off tomorrow. I'll post the results.
Thanks for the advice, Dave and James. I would never attempt this without the Brickboard providing access to knowledgeable people like you.
-- Bruce
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-- Bruce / '82 244 (315k miles!), '86 745, '87 760Ti, '94 854
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