Update 1-JUL-2008
Thank you again to
N*Caddy and
ewill3rd for your invaluable help thus far.
I looked at the pics of the fuel rails posted by
N*Caddy. The fuel rail on my car is metal. It seems that the previous owner did a nice job of keeping everything up to date. (I know he had an extended warranty, and he may have been a stickler).
I checked for fuel spray from the fuel rail with its Schrader valve open. Fuel sprayed -- but whether it was "really really spraying", I don't know.
I bought a High Energy Ignition spark tester as suggested by
ewill3rd. I tested all front-bank plug wires plus the outside wires on the rear bank. All appeared to spark without missing, so I concluded that lack of spark is not causing the problem. (Even in the unlikely event that the two untested inner wires on the rear bank were bad, I'd imagine the engine would still start).
I listened for pump whirring in the gas tank after turning ignition to "on" (with engine off). Whirring is present for a brief time so pump fuse is not causing the problem.
However, if I understand correctly, there are two fuel pump relays, and I wonder if "ignition on" test engages both or just one, and whether I need to run a test on a second relay?
Next I replaced the fuel filter. After this the car started right up! I went inside to wash-up, figuring I'd let the battery charge a little while idling before a test drive. As soon as I touched the gas pedal upon returning though, the car started idling rough, and after about two minutes it stalled. There appeared to be no codes not related to stall.
Now it behaves as it did prior to installing the new fuel filter: it turns over but won't start.
I bought a fuel pressure gauge as suggested by
ewill3rd. 10 psi after key to on position; 10 psi while turning over trying to start. (According to Haynes, 97 N* pressure should be 48-55 psi; I tried previously without success to get a "real" manual, what are they called, Helm?)
If replacing fuel pump weren't expensive ($300 part), seemingly difficult ('97 means drop tank) and potentially dangerous (novice meets gasoline), I'd replace the pump. But because of the expense and difficulty of replacing the pump, I want to rule out all other possibilities before attempting.
Could something related to failure of one of two pump relays cause the 10 psi issue, and if so can I test for such?
Also, three different sources have indicated a bad fuel pressure regular (FRP) can cause low pressure -- this by failing open and allowing fuel to return back to tank too easily. (Something different from a leaking diaphragm). A suggested test for FRP fail open is to restrict the fuel return line while monitoring pressure with gauge, but I've heard this can damage the return line.
Is there any way to test for a FRP failed open?
(I don't think removing the FPR vacuum line is the correct test for FPR failed open).
In light of cost & difficulty of fuel pump replacement, I'm contemplating "throwing a FPR at it". I do not want to try and drop the tank and replace the pump only to find that pump wasn't causing the problem.
The car appears to hold what little pressure is in the fuel line -- for example, if I test at night and remove something from fuel line the next morning, fuel spays all over -- so I don't think there's a leak anywhere.
Any thoughts are welcome.
In the mean time I'll start familiarizing myself with what I suspect will be my next endeavor -- fuel pump replacement instructions:
http://www.cadillacforums.com/forums...tructions.html (Fuel pump replacement instructions)
(By the way,
N*Caddy if you see this, I just got a PM you sent ~ a month ago about prices of shocks. I guess I'm not very internet savvy, but I appreciate the message and I hope it all worked out for you).