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hey all 2005 ford focus 2.0 automatic (4f27E) 77k.complaint of hard starting but ran fine after engine had started.(at first problem was intermittent). Owner has put a fuel pump (just pump with pick up socks and fuel filter)s in it(years ago),plugs coil boots. Mass air flow replacement. Idle air control valve cleaning. Throttle body decarbonization,FUEL RAIL PRESSURE SENSOR REPLACED All with a no success rate. On the 2005 – 2011 ford 2.0 and various engine ford uses an electronic return less fuel system.it has a unique way of regulating fuel pressure.it uses a sensor (FUEL RAIL PRESSURE SENSOR) with engine vacuum to limit fuel pump motor speed. May or MAY NOT COMMAND A CHECK ENGINE LIGHT. Check engine light was illuminated AFTER KEY ON ENGINE RUN TEST WAS COMPLETED.FUEL RAIL PRESSURE SENSOR OUT OF PEFROFRMANCE/RANGE.THERE IS A PID (parameter identification) for the fuel rail pressure sensor.(no shredder valve)it will read a percentage AND VOLTAGE..with key on engine off fuel pressure did not bleed off excessively. WHILE CRANKING ENGINE FUEL PRESSURE DECREASED DRAMATICALLY. Shows a drop from 78% to 25% down to as low as 10% while cranking. fuel pump sounded very rough and loud..fuel pump primed but doesn’t kick on while cranking. Priming the key multiple times seemed unhelping to resolve this issue.as we can see their is a fuel issue here. why is this vehicle loosing so much fuel pressure??. Upon removing fuel tank and fuel sender assembly. it didn’t show any signs of broken in tank fuel lines. Strainers weren’t clogged up. Wiring was inspected using a voltage drop. All within specifications.so naturally this had to be inside of the fuel pump assenmbly.i deiced to go with a gut instinct since I had no where to turn and replaced the assembly while the tank was removed. Upon installing a new fuel pump/fuel sender assembly,Hard start had COMPLETLY VANISHED! After vehicle has stopped hard starting another key on engine run test had been performed with no codes for the computer to report back with. Vehicle has had 500 miles put on it and has had zero drivability issues since. If you had the mtx-5 (manual transmission there is a re-flash for the computer. You may still have other issues causing your hard start but this vehicle had a fuel delivery issue. Thank you and have a great one ladies and gentlemen
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Awesome post. In-depth testing and analysis. Good troubleshooting methods.
On some vehicles with a vacuum controlled fuel regulator, if I suspected a fuel pressure issue, I would purposely pinch the regulator fuel return hose and force maximum fuel pressure to the rail… I mention this only to see if this would have been an option on your sensor controlled fuel pressure system.
Based on your initial complaint, I would have guess slow disintegration of the fuel filter causing a restriction in the lines causing a reduction in fuel pressure, but I guess it was the poor performing fuel pump. I believe that with a proper scan tool or oscilloscope one could have ‘current ramped’ the fuel pump circuit to see if the amperage draw was within spec.
If disconnected it would go into a base strategy.its a weird looking sensor.I got thrown for a loop because the car didn’t hesitate or stumble at any speed (indication of a fuel delivery issue). and everything seemed normal compared to a known good focus.I had failed to mention that I had gone threw all vacuum sources with startingfluid,propane.twisted them around and watched for a change on the o2 sensor.I would agree that a scope would’ve helped further diagnose it.people say scopes are on the way out but I say they’ve never left and are very important to diagnosing electrical issues
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