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I'm reading the 700/900 FAQ until I can't see anymore......so, here's my story:
Wasn't bad enough at Monticello Motorsports Country Club my "student" crashed us in his BMW M3 into the tire wall on his fifth lab, my sore neck put me out of action the rest of the day.
Driving my '89 740 turbo home in 35MPH Friday afternoon rush hour traffic, the engine suddenly would not take any throttle input. Just made it to a safe parking lot, then the engine wouldn't restart.
It wasn't like a sudden electrical shut-off, but like the car was in "limp home mode" and wouldn't exceed 2800 RPM (although I didn't look at the tach)
Cranked fine. Had spark. Disconnected the AMM for "limp home mode". No good.
After several other checks, concluded it had no fuel delivery. I disconnected the fuel line at the rail and got only a drip.
towed sixty miles home.
Next day, no start. Occasionally a little "bump' like it wanted to.
Several checks on fuel delivery electrical revealed:
3/4 tank of fuel
Fuel pump no sound upon key to run.
Fuse 1 pulled for Main fuel pump = 12.5v across terminals/ 10.2v cranking
Fuse 11 pulled for In Tank pump = 12.5v across terminals/ 10.2v cranking
(FAQ says voltages are in 5.5v range with engine running, but how do I check this since engine would quit if fuses are pulled?)
Replaced fuel relay with others = no help
Pulled fuel relay and jumped pins 82 & 30 = BOTH pumps run!
Fuse 13 pulled for Fuel Injection System = no voltage, any state
(this circuit looks like it runs the EGT to ECU signal)
Cleaned up FI grounds, Ignition Amplifier, AMM connector, etc. = No start
Unhooked AMM for "limp home mode" (just for kicks) = engine starts & runs.
Try replacing this AMM, and do another "lip home mode" test = won't start.
I didn't think the crash at the track did me in this much! But I am three afternoons with this car and still stumped!
Will test voltage at the fuel pump itself, check RPM sensor, and wiring of EGT.
Then what?
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