No Fuel - PCM or Pump?
#21
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
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
#22
New fuel pump. new fuel pump module. No pressure to motor ??
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
#23
Getting 12 volts at pin +9 and pin -2
Great! I pulled the back seat out and located the Fuel Pump control modules as Paul described, as well as the big rubber plug on the passenger's side under the seat, above the tank with the connection to the fuel pump.
I did find the video on youtube to cut the hole, and as a former sunroof/t-top installer, cutting the hole will be nothing and I can put it back sealed up and pretty very easily.
Chris, my particular year doesn't have the shrader valve, I've seen what you're talking about but they didn't manufacture it with one. Nevertheless, it's 0 psi key on or off.
So I found a wiring diagram with extensive online searching which shows the pinout on the fuel pump module. This makes troubleshooting terribly easy. Check this out...
Unplug the fuel pump module.
Turn it facing you where the top row has 6 wires, and the bottom row has 2 on left, 2 on right.
Top row is pins 1-6 from left to right
Bottom row is pins 7-10 from left to right
Pin 1, PCM input, brown
Pin 2, Ground to body, black
Pin 3, Fuel pump ground, yellow
Pin 4, Throttle screen, black/green
Pin 5, Fuel pump screen, white
Pin 6,
Pin 7, PCM output, white
Pin 8,
Pin 9, Switched battery positive, brown/green
Pin 10, Fuel pump positive, red
WARNING!!! PLEASE NOTE: if your wiring is different, or touching the wrong wire terminal could fry your PCM Computer or more... proceed at your own risk.
Since I'm getting no fuel pressure at all...
I put my digital volt meter + on pin 9, - on pin 2, turn the key to run position and see voltage. That tells me that I have a ground, and my fuse, relay, and inertia switch are all working.
Turn off the switch and make 2 little jumper wires.
With it still unplugged from the Fuel Pump Module, jump pin 2 ground, to pin 3 fuel pump ground
Also jump pin 9 switched battery positive to pin 10 fuel pump positive
Watch the fuel pressure gauge, and turn the switch to the run position for 2 seconds
If you see normal pressure, the fuel pump module is bad. If you don't see any pressure on the fuel pressure gauge (actually it should be 40-50psi, the fuel pump is bad.
In my case, I didn't see any pressure on the gauge, not even a movement of the needle; so I'll be replacing the fuel pump.
Thanks guys!
I did find the video on youtube to cut the hole, and as a former sunroof/t-top installer, cutting the hole will be nothing and I can put it back sealed up and pretty very easily.
Chris, my particular year doesn't have the shrader valve, I've seen what you're talking about but they didn't manufacture it with one. Nevertheless, it's 0 psi key on or off.
So I found a wiring diagram with extensive online searching which shows the pinout on the fuel pump module. This makes troubleshooting terribly easy. Check this out...
Unplug the fuel pump module.
Turn it facing you where the top row has 6 wires, and the bottom row has 2 on left, 2 on right.
Top row is pins 1-6 from left to right
Bottom row is pins 7-10 from left to right
Pin 1, PCM input, brown
Pin 2, Ground to body, black
Pin 3, Fuel pump ground, yellow
Pin 4, Throttle screen, black/green
Pin 5, Fuel pump screen, white
Pin 6,
Pin 7, PCM output, white
Pin 8,
Pin 9, Switched battery positive, brown/green
Pin 10, Fuel pump positive, red
WARNING!!! PLEASE NOTE: if your wiring is different, or touching the wrong wire terminal could fry your PCM Computer or more... proceed at your own risk.
Since I'm getting no fuel pressure at all...
I put my digital volt meter + on pin 9, - on pin 2, turn the key to run position and see voltage. That tells me that I have a ground, and my fuse, relay, and inertia switch are all working.
Turn off the switch and make 2 little jumper wires.
With it still unplugged from the Fuel Pump Module, jump pin 2 ground, to pin 3 fuel pump ground
Also jump pin 9 switched battery positive to pin 10 fuel pump positive
Watch the fuel pressure gauge, and turn the switch to the run position for 2 seconds
If you see normal pressure, the fuel pump module is bad. If you don't see any pressure on the fuel pressure gauge (actually it should be 40-50psi, the fuel pump is bad.
In my case, I didn't see any pressure on the gauge, not even a movement of the needle; so I'll be replacing the fuel pump.
Thanks guys!
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?
#24
12 Volts
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.
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.
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