Is key off power at Fuel Pump + normal?

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Is key off power at Fuel Pump + normal?

Post by kjschaudt » Sat Jun 11, 2016 10:36 pm

Is slowly decaying power at Fuel pump Positive lead normal after the key is turned from Run to off?

Debugging a strong crank but almost no start condition on 2002 'bird. Cranks well and will start for 30 seconds about once every day. Main codes noted were P1237 - Fuel pump primary circuit malfunction, Code: B1681 - PATS transceiver fault, Code: U1262 - SCP Data Link Fault, Code: P1641 - Fuel Pump Primary circuit failure, and Code: B1201 - Fuel sender circuit failure.

No fuel pressure at manifold. replaced filter, no fuel coming through filter.

Ran through the the Ford Manual diagnostics under these headings, replaced fuse, burnt relay and diode just in case. Pinpoint tests leave me with the impression that there is a short to power. Since the fuel pump wires didn't match the color shown in the manual, I bought a new pump at autozone to figure out the wiring. Plugged it in for grins as a bench test and it ran.

Disconnected both fuel pumps, probed connectors. After an extended period off, I checked key off power at the FP positive lead. NO POWER. Turned key on and found 12 volts power. Power remained when I turned the key off and removed it. Power slowly counted down and took 20 minutes to get down to 6 volts. Pulled rear fuse box relays and fuses without killing the decaying power.

Is this normal? Could a slowly decaying voltage mean a short between the FP wiring and perhaps something on a timer (exterior lights?)

Hooked up both original main and transfer pump and can definitely hear the main pump running with stethoscope. Maybe yes on jet pump. Tried cranking but still won't start.

Will try another pressure test tomorrow. Wondering if "priming" the system by pulling fuel to the schraeder valve with a hand pump will help.

Thanks, Ken

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