Alright, so I finally spent some time testing on Saturday. Before that - a quick symptom update. The car runs great the first time I start it everyday, and hesitates/stumbles for a minute or so everytime I stop/restart. More information on that further down...



Fuel pressure (pumps running, engine not running, using vacuum pump to adjust pressure via fuel pressure regulator vacuum port):

48 psi (0 psi vacuum)
46 psi (2.5 psi vacuum)
43 psi (5 psi vacuum)
41 psi (7.5 psi vacuum)
38 psi (10 psi vacuum)
36 psi (12.5 psi vacuum)

Couldn't pull a harder vacuum with the vacuum pump after this. The specs (Bentley) said that the fuel pressure drop should be equal to the vacuum increase. My measurements seem to match that.

Just to be sure, I measured the fuel pressure with the car running:

48-49 psi (FPR vacuum line removed and plugged)
40 psi (FPR vacuum line re-attached)

That also matches what the Bentley says - so the FPR *seems* to be working fine.

BUT, after shutting down the engine, fuel pressure is gone (0 psi) within 1-2 minutes. Hm. Pulled the fuel rail and ran the pumps - no leakage (did replace with 16 valve injectors, since it was on my list ;)). Pulled the cold-start injector, too - no leakage. Looked under the car...no leakage! Faulty check valve on the brand new Bosch fuel pump? Didn't want to pull all of that again, figured I would see if you guys had any thoughts first.

I checked a few other things along the way - cleaned the IAC, checked it and the TPS using Bentley specs. IAC checked out, TPS did not match specs*** (900 with throttle close, 2900 at WOT). I pulled a used one out of the parts stash and threw it in even though it was off, too (1000 at closed throttle, 2600 at WOT). Might need to buy a new one at some point.

The intake hose had some issues as well..ScanTech. Had a spare (well, now the 242 doesn't have one ha!). Didn't seem to improve anything noticeably, but I'm happy I found the problem before it fully gave up.



Also popped the access cover off to check the in-tank pump. Found a mess of wires with butt connectors from a previous poor patching attempt. Don't have a spare sender, and the pigtails off the sender are extremely short (<1 inch), so I used ScotchLoks for now. Pump fired right up - will be replacing the sender when I find a used one.



I didn't want to fiddle with the fragile fuel level sender wiring, so I didn't pull the unit - might still have a hole-y hose in there.

I am most suspicious of the system's inability to hold pressure after shutdown - the fuel-level-sender hose isn't relevant to that issue. So, what do you all think?


Other notes and such (not relevant to diagnosis):

16-valve injectors - plastic and much lighter. Idle is smoother than with the 350k-mile 8-valve units.



***Don't know if this is in the Bentley errata yet: Bentley says to measure the resistance across terminals 1 and 2 - actually, you need to measure across 1 and 3. This is for LH3.1.