Tony and Mike,

I found a reply from Mike in posts automatically locked for moderation in which he asks you to eMail him about a fuel pressure issue.

This is a FORUM. The idea is we share knowledge and information in PUBLIC for the benefit of all members. If everyone began communicating by PM or eMail, it wouldn't be a FORUM - it would be a MAILBOX.

Graham

 

Hey guys so I got 04 jag x-type 3.0 with these new parts in it n a new fuel filter n still have no pressure goin to the motor to make it run and it runs when a manually pressurize the fuel to the motor. My fuel kill switch is good n working idk what else to do. If anyone can help I would appreciate it

 

Okay, I've no fuel pressure after a jump using highest amps on a snowy wet day. So, I'm getting 12 volts, (11.9 v) with ignition on at pin 9 and 2 as specified. I'm assuming the modulator or the pump is bad. Now to test the modulator? Any way?

 

Is what most people believe is needed. As long as the key is on, there’s gonna be 12 volts. With the fuel pump, like fuel injectors, ground is most important as it controls the duration the pump is on.

Put a voltmeter on the yellow wire coming out of the fuel pump module & chassis ground.

Turn the key on & you’ll see it at zero volts for a second & then go to 12 volts. What?!!! 12 volts seen here is actually coming back from the pump. Why? Because the fuel module is open.

The ECU sends a low current PWM signal to the fuel pump module. The module acts as a buffer amplifier. As long as the fuse & inertia switch isn’t tripped, you’ll have 12 volts on the heavy red wire. This is where most go wrong & assume the fuel pump module is okay.

It’s the yellow or switched ground that makes the pump work. Kinda like why raise the bridge when you can lower the river... When the ECU commands fuel or more pressure, the yellow wire ground is enabled & the pump is on until the desired pressure is reached. Then poof, it goes away to 12 volts. Ground here is not a direct chassis ground, it’s a switched ground controlled by the fuel pump module.

This is because it’s a typical Ford single line fuel system without a return. The ECU controls the pressure/speed of the pump by varying the duration of the ground to the fuel pump.

It’s actually simple. It’s easier to see/ comprehend if you have an oscilloscope. But a voltmeter or even a test light that shows green for 12 volts or red for 0 volts will work.

Suspect the pump? A simple resistance test should read under 1 ohm. My defective pump was 2.7 ohms. Even with 12 volts direct, the pump wouldn’t turn.

It’s difficult to hear the pump run when the key is turned on because the pump is on for less than a second. Once the engine starts, can still be difficult to hear- at least for me.

With the key off, disconnect the connector under huge rubber plug under the rear seat. Gives you access to the pump harness.

Here you can easily check resistance. Can also do the same at the fuel pump module connector by back-probing it after disconnecting from the module. The other thing you can do is connect 12 volts directly ti the pump if you suspect it.

I disconnected the output fuel filter & attached a hose to the end of the filter to collect the fuel as the pump was supposed to scream- but nuttin until the pump motor was replaced.

This is tricky & something that could get you into trouble if you’re not on the correct pins. Don’t do it if you’re not sure.

Made up a fused test cable with a switch as you never ever want to connect a battery direct unless you don’t care about possibly seeing smoke.

Believe this should help. Please don’t PM me.