Mercedes Mullins
Bypassing a fuel pump relay involves manually powering the fuel pump to start the car. This is done by jumping or bypassing the fuel pump relay, which puts a constant +12VDC to the fuel pump. This means that voltage goes directly from the battery to the fuel pump, even when the engine is off. This can be achieved by using a jumper wire or a toggle switch. However, bypassing the fuel pump relay can be dangerous, as it can lead to fuel continuing to run if the engine stops, which can cause a fire in the event of an accident. It is important to note that this procedure may vary depending on the specific model and year of the Ford diesel vehicle.
Characteristics and Values Table for Bypassing Ford Diesel Fuel Pump Relay
| Characteristics | Values |
|---|---|
| Reason for bypassing | To avoid repeated turning of the key to drain the fuel tank |
| Solution | Jump the FPCM, check for faulty FPCM or PCM |
| Steps | Check fuse F56, check for voltage across the fuse, check for ground on pin socket 2, put a jumper wire between pin sockets 3 and 5 |
| Additional steps | Ensure FPCM connector is plugged in, bypass fuel pump relay in the fuse block, not FPCM connector |
| Additional advice | Check for 12v on pin 2 of the relay socket, ground will come from the Body Control Module (BCM) |
| Safety advice | Bypassing the fuel pump relay puts a constant +12VDC to the fuel pump, even with the engine turned off |
| Safety feature | Fuel pump relay design allows the relay to be picked by coil pulses so that the fuel pump only runs when the coil is firing the engine |
| Safety concerns | Bypassing the fuel pump relay may be unsafe in the event of a serious accident |
| Alternative solution | Artificially power the relay |
| Alternative solution 2 | Install a very high-performance fuel pump |
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What You'll Learn
Check fuse F56 (30A) and fuel pump relay
To check fuse F56 (30A) and the fuel pump relay, you must first locate the fuel pump relay in the vehicle's fuse box. Typically, the main fuse box is located under the hood near the front of your vehicle. However, there may also be a smaller fuse box situated under the steering column inside the vehicle. To access the fuse box, simply pull off its cover. The diagram printed on the cover will indicate the location of the fuel pump relay, which is usually coloured green or grey.
Once you have located the fuel pump relay, remove it by pulling it straight out from the fuse box. If it doesn't come out easily, try rocking it gently back and forth to loosen the connection before pulling it out again. Please note that removing the relay will disable the fuel pump, preventing the engine from starting.
To check the fuse, you can use a voltmeter. With the key off, take the relay out and place your voltmeter on pin sockets 1 and 3 of the fuse block. If you have 12 volts on both sockets, proceed to check for ground on pin socket 2 with the key on. This step may require assistance, as the Body Control Module (BCM) will only provide ground on that wire for a few seconds, which is just enough to prime the fuel system.
If the engine doesn't start after this, the BCM will drop the ground and look for a signal from the crank position sensor. If you get a ground there, use a jumper wire to connect pin sockets 3 and 5, and then attempt to start the vehicle. This action bypasses the fuel pump relay and the BCM ground, sending power directly to pin 1 of the FPCM.
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Test for 12v on pin 2 of the relay socket
To test for 12v on pin 2 of the relay socket, you will need to identify the correct pins. A common fuel pump relay has four electrical terminals or pins sticking out of its base. These pins are numbered, and you can refer to the diagram stamped on the relay case to identify each pin. Once you have located pin 2, you can proceed with the test.
It is important to note that before performing any electrical tests, ensure that the power source is disconnected for safety reasons. Now, to test for 12v on pin 2, you will need a digital multimeter. Set the multimeter to the appropriate setting, typically the voltage measurement setting. Touch the positive lead of the multimeter to pin 2, and touch the negative lead to a known ground point. This will complete the circuit, and you should get a voltage reading on the multimeter. A reading of 12v indicates that the circuit is functioning correctly, and voltage is reaching pin 2 as expected.
If you do not get a reading of 12v, there may be an issue with the circuit or the relay itself. In this case, you will need to perform further troubleshooting steps. First, check the fuse associated with the circuit to ensure it is not blown. If the fuse is blown, replace it and retest for voltage at pin 2. If the fuse is fine, move on to checking the wiring harness and connectors for any signs of damage or corrosion. Corroded terminals can be cleaned with electrical contact cleaner.
If the voltage is present at the fuse but not at pin 2, there may be a break in the wiring between the fuse and the relay. Work your way along the wire, checking for any signs of damage or loose connections. Pay particular attention to the crimp connectors as they are commonly prone to issues. If you find any damaged wiring, repair or replace it as necessary. Once the repairs are made, retest for voltage at pin 2 to ensure that the issue has been resolved.
By following these steps and testing for 12v on pin 2 of the relay socket, you can effectively diagnose and troubleshoot issues related to the fuel pump relay circuit in your Ford diesel vehicle.
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Bypass the fuel pump relay with a jumper wire
To bypass the fuel pump relay with a jumper wire, you will need some basic tools and a good understanding of your car's electrical system. Here is a step-by-step guide to help you through the process:
Locate the Fuel Pump Relay:
Begin by parking your car on flat ground and opening the hood to access the engine bay. The fuel pump relay is typically located near the fuse box or battery terminals. However, it is always a good idea to refer to your car's owner's manual to identify its exact location.
Disconnect the Battery Terminals:
The next step is to carefully disconnect the battery terminals. You will need to remove the black negative cable, but you can also remove both cables if you prefer. This step is crucial to ensure your safety and prevent any accidental short circuits.
Identify the Correct Pins:
You will need to identify the correct pins on the fuel pump relay to connect the jumper wire. The relay should have a diagram indicating which contacts are the switch and control contacts. Look for pins labelled 85, 86, 87, and 30. These pins are typically located at the top right and bottom left of the relay.
Connect the Jumper Wire:
Use a suitable gauge wire, such as 12 or 14 AWG wire, to create your jumper connection. Strip both ends of the wire to expose the copper. Connect one end of the stripped wire to the pin slot on the upper left of the pump relay center (typically pin 87). Connect the other end to the pin slot on the lower right (typically pin 30).
Test the Connection:
Once the jumper wire is connected, carefully reconnect the battery terminals. Turn the ignition key to the "on" position and observe whether the fuel pump primes. If you hear the pump engaging, your bypass was successful.
It is important to note that bypassing the fuel pump relay is a temporary solution and should not be left as a permanent fix. Always replace the fuel pump module or address any underlying issues as soon as possible. Additionally, consult a professional mechanic if you are unsure about any part of this process.
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Use a toggle switch to control the fuel pump
Bypassing the fuel pump relay in a Ford diesel engine can be done by using a toggle switch to control the fuel pump. This method involves "hot-wiring" power from the fuel pump fuse, through the fuel pump relay, and directly to the fuel pump in the tank.
Firstly, locate the fuel pump relay in the fuse box or relay panel. This can usually be found in the vehicle's fuse box or relay panel, and the correct relay can be identified by checking the diagram on the cover of the fuse box. Once located, use a screwdriver to gently remove the fuel pump relay from its socket.
Next, identify the terminal pins on the relay socket, which usually consist of four or five pins. The power source, typically leading to the battery, needs to be connected directly to the pin that powers the fuel pump. This connection can be made using wire or jumper cables. Then, connect the other end to the appropriate terminal on the relay socket. If necessary, connect a ground wire from the relay socket to the vehicle's chassis.
With the connections secured, turn the ignition key to the "on" position without starting the engine. If you hear the fuel pump activate, it indicates that power is being supplied correctly. Now, you can attempt to start the engine. If successful, you have bypassed the fuel pump relay.
It is important to note that this method is only a temporary fix, and a faulty relay should be replaced as soon as possible to prevent further issues. Working with a vehicle's electrical system can be dangerous, so ensure that all connections are secure and insulated to prevent short circuits or sparks. Additionally, bypassing the relay can lead to a direct connection between the battery and the fuel pump, which may overload the circuit if the pump draws too much power. As such, it is recommended to have a professional mechanic inspect and replace the faulty relay after performing this temporary bypass solution.
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Install a secondary relay to reduce load
Installing a secondary relay is a great way to reduce the load on the primary relay in the CJB (Central Junction Box) of your Ford diesel engine. This method is particularly useful if you have added a second fuel pump or a high-capacity pump, as it bypasses the fuel pump load sense circuit.
Firstly, you'll need to identify the location for your auxiliary relay. You have two options: the pass footwell or the pass side engine compartment. Once you've decided on a location, you can begin setting up the wiring.
The wiring process starts by using the OE circuit through the inertia switch to power on the relay. This setup ensures that the new relay takes the contact hit from the HFCM, reducing the load on the primary relay. It's important to note that this method does not sacrifice the PCM control or the fuel pump sense circuit.
Additionally, you can consider waterproofing your secondary relay as a precaution, especially if you anticipate any exposure to moisture. This can be a useful measure to protect your engine and ensure the longevity of your setup.
By following these steps, you can successfully install a secondary relay to reduce the load on your Ford diesel fuel pump relay, improving the performance and reliability of your engine.
Frequently asked questions
First, check for 12v on pin 2 of the relay socket. If you have power, then ground will come from the Body Control Module (BCM) and go into pin 1 relay socket. If there’s no ground when the key is on, then there’s an issue with the BCM or the wire from the BCM to the relay. You can then install direct power to the fuel pump from a spare battery through a spare fuel pump connector.
The fuel pump relay is a safety feature that only runs when the coil is firing the engine. This means that when the engine turns off, the fuel system turns off.
Bypassing the fuel pump relay puts a constant +12VDC to the fuel pump, meaning there is voltage directly from the battery to the fuel pump even with the engine turned off. This could be dangerous in the event of a serious accident.
