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Fuel Pump Testing Z4 & Z4M
 
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Pelican Technical Article:

Fuel Pump Testing Z4 & Z4M

Nick Czerula

Time:

3 hours3 hrs

Tab:

$0

Talent:

*****

Tools:

Phillips & flathead screwdriver, socket set

Applicable Models:

Z4 M54 (2003-05)
Z4M S54 (2006-06)
Z4 N52 (2006-06)
M3 (N/A-A)

Parts Required:

Fuel pump, fuel pump sealing O-ring

Hot Tip:

Check fuse before digging too deep

Performance Gain:

Properly functioning fuel pump

Complementary Modification:

Replace fuel filter

The fuel supply system in a BMW Z4(M) consists of:

  • Fuel tank.
  • Fuel filler with associated breathing and venting pipes.
  • High pressure fuel pump assembly with fuel filter and fuel level senders.

The fuel tank is two-lobed. There is one fuel level sender, located in the right side of the tank mounted to the bottom of tank. The right fuel tank lobe holds the fuel level sender, fuel filter and the fuel pump.

In tank fuel pumps have many benefits. The pump is submerged in fuel keeping it cool, preventing vapor lock and electrical issues. The fuel pump delivers a constant flow of gasoline to the fuel rail at a regulated pressure and volume. The fuel pump draws fuel from the fuel tank and pushes it through the fuel filter, mounted outside of the fuel tank.

The EKP control module controls the speed of the fuel pump by means of pulse width modulation of the EKP output voltage according to the fuel request. The coding of the module in conjunction with the DME software determines fuel delivery. The data is delivered over a CAN bus. The EKP control module is located in the trunk on the right side behind the battery.

When the key is turned on the EKP module activates. The fuel pump is then activated at 100% for engine starting. On completion of the starting, the EKP control module regulates the EKP according to the supply rate set by the DME.

If there is no communication with the DME for example, a CAN bus failure occurs and the EKP control module switches to emergency operation. The electric fuel pump is then run at 100%.

A faulty fuel pump can cause poor engine performance and hard starting problems. When it fails completely, you may be left with an engine that doesn't start. If you suspect your fuel pump has failed, you can confirm the fuel pump has received the correct voltage when commanded ON by the fuel pump relay using a digital volt ohm-meter (DVOM). If the correct voltage is present, but the pump does not activate, the pump is likely faulty. Use the DVOM in conjunction with a wiring diagram to determine the correct terminals for testing. On some models, the fuel pump is controlled by an electronic control module (EKPS), this module can fail, not sending adequate voltage to the fuel pump.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Pressure testing:
Models with S54 6-cylinder engine: You will have to connect a T-adapter to test fuel delivery pressure.
Figure 1

Models with S54 6-cylinder engine: You will have to connect a T-adapter to test fuel delivery pressure. Z4M models do not have a fuel pressure test port. First, relieve fuel pressure. Remove fuses F4 and F44 in the power distribution panel, crank the engine until it doesn't start. Reinstall the fuses. Then working at the fuel delivery line on the left side of the engine (red arrow), press the plastic collar toward the line and hold while you slide line off the engine. Cover line in rag to catch any dripping fuel. See following step.

Working at the fuel delivery line on the left side of the engine (red arrow), press the plastic collar toward the line and hold while you slide line off the engine.
Figure 2

Working at the fuel delivery line on the left side of the engine (red arrow), press the plastic collar toward the line and hold while you slide line off the engine. Cover line in rag (red arrow) to catch any dripping fuel. You will have to connect a T-adapter (yellow arrow) to test fuel delivery pressure.

Follow the instruction for your test kit and install the T-adapter (yellow arrow).
Figure 3

Follow the instruction for your test kit and install the T-adapter (yellow arrow). Then connect your fuel pressure gauge to the adapter (red arrow). Next, start or attempt to start engine. Fuel pressure should be: S54 6-cylinder: 5.0 bar +/- 0.2 (72.5 psi +/- 3). NG6 engine should be similar pressure.

Electrical testing:
The fuel pump module (EKPS) in BMW Z4 models is located in the right side of trunk, behind the battery hidden by carpet trim (red arrow).
Figure 4

The fuel pump module (EKPS) in BMW Z4 models is located in the right side of trunk, behind the battery hidden by carpet trim (red arrow).

Working in trunk, lever out the two plastic trim clips (red arrows) using a trim panel tool.
Figure 5

Working in trunk, lever out the two plastic trim clips (red arrows) using a trim panel tool.

Lift carpet trim and remove from the trunk by sliding it straight out toward the left side of the vehicle.
Figure 6

Lift carpet trim and remove from the trunk by sliding it straight out toward the left side of the vehicle.

The fuel pump module is located under the battery connection junction (red arrow).
Figure 7

The fuel pump module is located under the battery connection junction (red arrow). Start by disconnecting the module connectors (blue arrows). Press the release tabs and pull the connectors straight out.

If you had no fuel pressure and want to manually activate the pump, connect fused jumper wires (yellow arrow) across the fuel pump connector (red arrow) terminals.
Figure 8

If you had no fuel pressure and want to manually activate the pump, connect fused jumper wires (yellow arrow) across the fuel pump connector (red arrow) terminals. Red with white is battery volts. Brown is ground. When powered up, your fuel gauge should display the specification noted earlier.

Connect DVOM across fuel pump terminals while backprobing (yellow arrows) then plug the connector (purple arrow) back in.
Figure 9

Connect DVOM across fuel pump terminals while backprobing (yellow arrows) then plug the connector (purple arrow) back in. These are the two terminals on my subject vehicle. You will be testing voltage across the large wires at the connector. Red with white is battery volts. Brown is ground. Turn key ON, DVOM (red arrow) should read battery volts (around 10 volts). If no voltage is found, check relay and fuel pump fuse. With key ON, fuel pump will receive voltage for a 3-5 seconds to prime system, (if engine doesn't start). I suggest load testing using a test light and a DVOM. Connect DVOM across fuel pump electrical connector terminals and take a reading, it should read battery volts when key is turned ON. Then connect an incandescent bulb style test light to battery ground and touch the test light probe tip the positive wire you are back probing with DVOM. Your reading should hold steady, a maximum drop in voltage of 0.5 volts is OK. Anything more is a problem. In this photo, voltage held steady. If you have no voltage the DME may not be activating the module or the module is faulty. You can also test voltage to the module. The blue and yellow wires on the left side of the connector are the CAN BUS communication lines. K-BUS is the white with red and yellow. The black with green (blue arrow) is ignition voltage to module (battery volts with key ON) from fuse 44 (5 amp fuse). Brown (green arrow) is the ground and white arrow is battery volts all the time from fuse 4 (20 amp fuse).

If you are concerned the module is not being activated by the DME, use a BMW scan tool to activate the fuel pump module (green arrow).
Figure 10

If you are concerned the module is not being activated by the DME, use a BMW scan tool to activate the fuel pump module (green arrow). Monitor the fuel pump output and use the specification mentioned earlier.

When activating the fuel pump using the key, the scan tool can also display voltage and current output.
Figure 11

When activating the fuel pump using the key, the scan tool can also display voltage and current output. If there is voltage and very low or no current (purple arrows), the fuel pump or wiring to the fuel pump may be faulty. You can also test voltage to the module when the key is ON. The blue and yellow wires on the left side of the connector are the CAN BUS communication lines. K-BUS is the white with red and yellow. The black with green (blue arrow) is ignition voltage to module (battery volts with key ON) from fuse 44 (5 amp fuse). Brown (green arrow) is the ground and white arrow is battery volts all the time from fuse 4 (20 amp fuse). The colored arrows on the scan tool indicate the terminal at the connector that signal comes from.

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Page last updated: Wed 12/7/2016 03:08:11 AM