I just got through replacing the heads on my 2000 5.4L Expy and after several attempts to start the truck, it appears that I am not getting fuel. I originally unplugged the inertia switch before I bled the fuel system and removed the injectors and had pressure when I dismantled it. After attempting starts, I press the bleeder on the fuel rail and get nothing. I can't hear the fuel pump, however I am confident that it worked before. Should I be able to hear the pump? Should I have turned the engine over with no plugs before installing them, etc. Any help would be much appreciated.

 

When you turn the iginition key to the "ON" position the fuel pump should run for about 2-3 seconds. Get under the truck near the fuel pump and have someone cycle the key to the "ON" position afew times. Each time they cycle the key you should hear the pump run.

If not, better get your DMM out and check for voltage, fuse #10 (20A) in the underhood BJB (Battery Junction Box), fuel pump relay, the inertia fuel shutoff switch, on back to the fuel pump.

 

So far, I have confirmed power to the fuse and relay. I also found power to the inertia switch, however it appears that I am only getting around 9 volts to the switch. Does 9 volts seem enough/correct? My next move is to check power to the module and then the pump. Does anyone know if the module is accessible without pulling the tank? Where exactly is it located.

 

9 volts is not enough. I believe the fuel module is mounted above the rear axle.

 

If you only have 9 volts at the input to the inertia switch, you've already found that the problem is "upstream", not downstream.

It's simple series circuit consisting of fuse F10, the closed contacts of the relay, the inertia switch, and the pump motor inside the tank plus the wire that runs the power.


Now, go back to the input and the output of the energized relay and the fuse and see where the last point is that properly measures battery voltage. The portion of the circuit between the last good reading and the first bad reading is the area that has the excessive resistance that is dropping voltage.

 

So far I traced it back to # 87 on the Fuel pump relay which is the green/yellow wire that comes from the PCM and also feeds the inertia switch. I plan on looking at the wiring on the PCM. Is this normal for a PCM?

 

Think of it the other way around. Current on the green/yellow wire doesn't "come from" the PCM. The current flows "from" pin 87 of the FP relay "TO" both the PCM and the inertia shut off switch.

I'm not sure how you measured the 9v at the IFS switch. Were you measuring the voltage at the green/yellow wire or the other wire at the IFS switch?

If you only have 9v at the inertial switch green/yellow wire, "back up" to pin 87 of the FP relay. How many volts do you have there? (Be aware, that pin 87 of the FP relay is only active for a second or two after you turn the ignition switch to the "ON" position.)

Then "back up" further to the input side of the FP relay - pin 30. How many volts do you have there?

 

Also, the voltage readings *MUST* be made during the brief interval when the fuel pump is supposed to be running during the start-up sequence.

 

I think I am making some headway. With the relay pulled I get roughly 16 volts at 30 and 9 volts at 87 with the switch on. When the relay is inserted and I probe the wire under the relay (87), I get 14 volts for a split second. I went to both wires (green/Yellow and pink/black) on the inertia switch connector and got 14 volts for just a second or two. Looks like my next feat is to the fuel pump module and fuel pump itself. Are there any wires I can check under the vehicle before I have to drop the tank to check the fuel pump? Thanks so much for the help!

 

Whoa! How many volts is your battery putting out?

Not good. How are you measuring that ? I'm assuming you have the relay out of the socket and are measuring the voltage at the socket where the relay's pin 87 normally is plugged in? I would expect 0 volts at the pin 87 socket with the relay out of the circuit..

That's better. It should read battery voltage (is your battery putting out 14 volts?) with the relay plugged in, but only for 2 to 3 seconds after the ignition key is turned to the "RUN" position. After 2 to 3 seconds it should go to 0 volts.

Again, how are you measuring this? Is the IFS switch out of the circuit and you are probing the harness connector? In that case you should see near battery voltage on the green/yellow for 2 to 3 seconds after the igniton switch is turned to the "run" position (with the fuel pump relay plugged in), and then dropping to 0 volts. And with the IFS switch out of the circuit, the other wire should always read 0 volts.

What is the "fuel pump modulue" you speak of?

Before dropping the tank, try applying battery voltage through a fused jumper wire to the pink/black wire of the IFS switch connector to see if the pump will run.

 

I was originally measuring 9 volts with the switch on and the relay pulled at terminal 87. When I did the test with the relay in it measured 9 volts and when the switch was turned to run it measured just over 14 volts for a couple of seconds. The 9 volt reading is what had me so confused a few days ago. Well, I just tested everything again and I am getting 0 volts at 87 with the switch on. Very strange...
Yes, my battery measures just over 14 volts.
I was going by the drawing in the haynes manual where it says fuel pump module. I take it that pink/black goes directly to the pump. BTW, the only codes that I am getting are low voltage. I will feed the pump with 12 (or 14) volts.

 

What would those codes be?

 

Right now I have a b1676, a b1318 and a b1869.

 

I'd clear those codes and see if they come back.
Have you had a booster battery on this truck lately?

I'd also verify and clean all the grounds.
Maybe you forgot a ground strap when you replaced the heads?

 

The battery is new and I am sure the the low voltage codes come from the old battery. Just for kicks, I tried another DMM and found that the 14 volt reading was really a 12 volt reading, so I think I am good there. I ran a fused wire from a 12 volt source and connected it the the pink wire with black stripe and got nothing. Strange that the fuel pump was working when I parked it. Well, looks like I will be dropping the tank tomorrow after I check my grounds. If I find that the pump is indeed bad, should I replace just the pump or the whole assembly while I have the tank down?