fuel question

[BobHyatt]

I am trying to help diagnose a problem remotely. My son has a 2000 GT, with a fuel pressure guage always connected. Car's been running fine for a long time, but this past weekend, it started to run really ragged as he was leaving to go somewhere and he noticed the fuel pressure was at zero. He verified this with a second guage. He could hear the pump turning so that was checking out and he made the natural assumption that the pump had gone bad such that the motor was turning but it wasn't actually building up any pressure. He replaced the fuel pump yesterday, and still no pressure. He can lay under the car and have someone turn the key to run and he can hear the pump run (new pump). He then tried a new pressure regulator, but still no glory.

The Haynes book we have is more for the older style fuel delivery system (with a return line) so it doesn't offer a lot of help. Any suggestions since this is not a relay/fuse/pump issue? He replaced the filter about 9 months ago. The car ran fine the last time he had it out, the next time it was barely running at all...

 

[hotcobra03]

fuel pump

maybe somthing fell off inside of tank?clogged fuel filter even though its been changed 9months ago ..someone could have put something into the tank and that was sucked up into filter,,,maybe he can unhook fuel line before fuel filter and see if fuel is being pumped before removing tank..ill see if i can post more for you

 

[hotcobra03]

fuel pump

Electronic Returnless Fuel System
The fuel system consists of a fuel tank with reservoir, fuel pump, fuel rail pressure sensor, fuel filter, fuel supply line, engine fuel temperature sensor, fuel rail, fuel injectors, and schrader/pressure test point. Operation of the system is as follows (Figure 65) and (Figure 66):

The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.
The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.
The PCM commands a duty cycle to the fuel pump driver module (FPDM).
The fuel pump driver module modulates the voltage to the fuel pump (FP) to achieve the proper fuel pressure. Voltage for the fuel pump is supplied by the power relay or FPDM power supply relay. (For additional information on FPDM operation, refer to PCM Outputs—Fuel Pump and PCM Inputs—FPM.)
The fuel rail pressure (FRP) sensor provides the PCM with the current fuel rail pressure. The PCM uses this information to vary the duty cycle output to the FPDM to compensate for varying loads.
The engine fuel temperature (EFT) sensor measures current fuel temperatures in the fuel rail. This information is used to vary the fuel pressure and avoid fuel system vaporization.
The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12 volt VPWR from the power relay. The ground signal is controlled by the PCM.
A pressure test point valve (schrader valve) is located on the fuel rail. This is used to measure fuel injector supply pressure for diagnostic procedures and repairs. ON VEHICLES NOT EQUIPPED WITH A SCHRADER VALVE, USE ROTUNDA FUEL PRESSURE TEST KIT #134—R0087 OR EQUIVALENT.
There are three filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/schrader valve.
The fuel pump (FP) module is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.
The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle (following a collision).

 

[BobHyatt]

When I got home we found the problem. Old fuel pump had caused the fuse to blow as it failed. We tested the old pump with a 12 v source and it would _slowly_ turn but would blow a 30a test-harness fuse, so it was bad. When we replaced the fuse the thing fired right up...

This varying the duty cycle using pulse-width modulation is an interesting approach...