yo,
as Krafty advised... ck the connectors first
on my 96 when I replaced sprak plugs, the connector on #4 looked ok, but it was just laying on fi and not making any contact electrically.
turn ign key to on - should hear fuel pump run
FUEL PRESSURE REGULATOR
Test; remove vacuum line & check for aroma of gas or gas in line; if any, replace the reg since the diaphram is damaged.
•Fuel Pump Power Circuit.
◦The other very important thing to do, before condemning the Fuel Pump is to make sure it's getting power.
◦This can be done by tapping into the Fuel Pump's power circuit with a Multimeter.
◦Once you're tapped in, have a helper crank the Engine while you observe your Multimeter in Volts DC mode. If Voltage is present (12 Volts), then you have confirmed that the Fuel Pump Fuse, Fuel Pump Relay and Inertia Switch are working perfectly.
◦Confirming power to the Fuel Pump (with a Multimeter) also verifies that the Fuel Pump has failed and needs to be replaced.
◦If no Voltage is present, as your helper cranks the Engine, then the cause of No Fuel Condition is due to either a BAD Fuse, Fuel Pump Relay, or Inertia Switch.
FP & EEC Power Relay Wiring Diagram in a 90
Source: by Seattle FSB (SeattleFSB) at
http://www.supermotors.net/registry/media/854315
&
Fuel Injector Test; "...With eveything connected normally & the key in RUN, pierce the TAN wire on any injector & tap it BRIEFLY to ground. Do you hear half the injectors click open & then closed? Put a finger on each one to feel which ones are working. If some of them don't open, repeat the test, holding the ground SLIGHTLY longer each time, but never more than 3 sec continuously...Repeat this for the 2nd bank of injectors (just one with a different color wire)..."
Wiring Diagram in a 90
Source: by SeattleFSB (Seattle FSB) at
http://www.supermotors.net/registry/media/851837
Operational Sequence;
The Control Module (PCM) runs the pump{s} for one second when it receives an ignition- on signal. It also runs the pumps as long as it receives a PIP signal from the Hall-effect devices, it continues pump operation even after the key is released from START. If the PIP signals fall below 120RPM, the control module cuts off the signal to the fuel pump relay. The pump will also run when the terminals of the fuel pump test connector are jumped. the Control module signals the pump when it receives a CRANK signal, and when the Control module gets PIP signals that the engine is running. the pump does not run if the PIP indicates the engine is not running even with ignition ON {except for that first one second}.
Testing, General; "...Misdiagnosis is the leading cause of fuel pump returns. If the engine runs but displays driveability symptoms that you suspect are fuelrelated (hard starting, hesitation, misfiring, power loss), first attempt to eliminate other possible causes of the problem. Make sure the engine is in good mechanical condition. An engine may not start or run properly for many reasons. BE SURE TO CHECK: Fuel in the vehicle tank is adequate (add 2 to 3 gallons as needed). Fuel is fresh and of good quality. Fuel system has no leaks. Fuel filter has been replaced. Fuel delivery electrical system checks OK. Engine mechanical systems check OK. Engine electrical system checks OK. Ignition system checks OK. Charging system checks OK. Battery voltage is at least 12.4 volts. Cranking voltage at the starter is at least 9.6 volts. Inertia switch is reset (typical of Ford applications). Oil pressure and RPM signals are present (various applications). THE MOST COMMON REASONS FOR REPEAT FUEL PUMP FAILURE ARE: Misdiagnosis: Pump is OK, fault lies elsewhere! Not measuring fuel volume. Not replacing fuel filter and strainer(s). Fuel contamination. Not properly cleaning and flushing inside of fuel tank. Not correcting vehicle electrical connector, wiring and ground issues. Not resetting a tripped inertia switch. Not checking for oil pressure and RPM signals..."
Source: by Airtex
