g6civcx
05-04-2006, 07:24 AM
Disclaimer
This thread was started in an effort to address common fuel pump questions. Zilvia.net and the author not responsible for content or misuse.
Always maintain a fire extinguisher meant for gasoline on hand, and do not smoke.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Background
If you suspect that you fuel pump is malfunctioning, symptoms can include impossible to start and you have verified that you have spark, fuel starvation, inoperative fuel pump, etc. The purpose of this article is to restore your fuel pump system to OEM specfications.
Go to zeroyon.com and download a copy of the FSM for your year 240SX. I will cover the DOHC S13 in this article. SOHC and S14s are similar.
Go to autozone.com and read the information available there on repair information. Select your vehicle from the choices available and look in the repair info section. They provide some basic information as well as some diagnostic and repair guidelines.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tools
* Multimeter - a good, high quality multimeter tool should be used to diagnose electrical problems. You can get one from any electrical supply store. I will not cover how to use a multimeter. Follow the instructions on the package or search google for directions.
* Screwdrivers and sockets - to remove trim panels.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
System Description
Look at the following picture for general system description. It's self-explantory.
http://img149.imageshack.us/img149/4867/fuelpump1gu2.jpg (http://imageshack.us)
The fuel pump itself is located in the fuel tank. There is an access panel located in the trunk compartment, near the US-right passenger side. This is where the blue fuel pump harness will be.
http://img365.imageshack.us/img365/7504/fuelpump2xt9.jpg (http://imageshack.us)
Let's walk through how the stock fuel pump control system works.
http://img365.imageshack.us/img365/9202/fuelpump3od6.jpg (http://imageshack.us)
1. Battery power is supplied via the E22 harness at the positive battery terminal.
2. Power passes through the fusible link located in Relay Box A located near the battery.
3. Power then travels to the ignition switch. When the ignition switch is turned to the ON position, power travels to the 15A fuse located in Relay Box A.
4. Power then travels to the fuel pump relay, also located in Relay Box A.
5. The fuel pump relay has 4 pins. 2 pins are connected to ignition power as described in #4. One pin goes to the ECU. One pin goes to the fuel pump itself.
When ignition power is available, the ECU can activate and deactivate the fuel pump. The fuel pump relay is normally open, i.e. no current flows to the fuel pump under normal conditions. To activate the fuel pump, the ECU draws current through the relay and the relay lets power flow to the fuel pump.
6. Fuel pump relay connection travels to the ECU through the firewall and to the ECU harness.
7. Fuel pump power travels to the fuel pump via the Super Multiple Junction (SMJ) located in the US-left driver side kick panel. It then travels via the body harness to the back of the trunk compartment.
Here are pictures of the locations of the various components.
http://img178.imageshack.us/img178/2530/fuelpump4rx2.jpg (http://imageshack.us)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preliminary Check
http://img365.imageshack.us/img365/4450/fuelpump5tw3.jpg (http://imageshack.us)
Have someone turn the ignition to ON. Listen for a faint, high-pitch noise as the fuel pump primes for several seconds. If you hear it, your fuel pump is getting power. If you continue to have problems, suspect a faulty fuel pump that is unable to maintain pressure or you have a leak somewhere in the fuel system.
Check your fusible link and fuse pump fuse. Inspect and replace as necessary. Sometimes a fuse can appear intact, but is in fact blown. Use your multimeter and measure for continuity between the two terminals of the fuse. If continuity doesn't exist, replace the fuse.
Check your fuse pump relay. Remove the relay. When you look at the pins of the relay, each pin is labeled with a number. Use a paper clip and jumper the 1 and 3 terminal on the wiring. If your fuel pump comes on with ignition, you have a bad relay.
Check the engine harness that runs under the US-left driver side front fender. This is common on 240SXs that has been lowered. The best way is to reroute this harness to the engine bay to avoid problems.
This is my friend and fellow Zilvia poster holding the harness.
http://g6civcx.angryhosting.com/S13/Tech/Harness.JPG
You should relocate this harness to the engine bay like so.
http://g6civcx.angryhosting.com/S13/Tech/harness2.JPG
These are the most common points of failure. Check them thoroughly. If you can't find anything, you will have to track down broken wires.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fuel pump check
Turn the ignition off and go to the trunk compartment. We will be working around this area to see if the fuel pump is getting power. PLEASE MAKE SURE YOU DO NOT SMELL FUEL. If you do, fix it immediately. Working with your multimeter may expose some sparks. Make sure you do not smell fuel.
For information about the fuel pump, including how to change it, read this article: http://www.zilvia.net/f/showthread.php?t=94575
Credits to the author for his contributions. This is him holding the fuel pump. You will be looking for that blue harness.
http://img.photobucket.com/albums/v317/bjorkluv/IMG_1921.jpg
Go find that blue harness and disconnect it. We will be working with the side on the fuel pump. Use your multimeter and check for continuity between the two wires going to the fuel pump. This harness is labeled 'C' in the circuit schematic.
What you're looking for is broken wiring somewhere in the fuel pump itself. If you do not get continuity, make sure you're checking the correct wires. If there's still no continuity, there is a broken wire or the fuel pump itself is defective. You can use bjorkluv's writeup to remove the fuel pump and repair, or look at the wires for damage.
If the fuel pump has continuity, we will go to the harness on the side of the body harness. We will be checking for power and ground.
http://img515.imageshack.us/img515/8689/fuelpump6zu3.jpg (http://imageshack.us)
Start by checking for continuity between terminal a and body ground. This is see if your ground wire is good. If you don't have continuity, follow the ground wire and repair the broken wire.
Now check for continuity between terminal c and pin 3 of the fuel pump relay. This checks to see if the wire described in #7 above is not broken. You will need a long wire to connect these 2 terminals. If you have no continuity, track down the broken wire and fix it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
ECU check
http://img515.imageshack.us/img515/8689/fuelpump6zu3.jpg (http://imageshack.us)
Check for continuity between pin 2 of the fuel pump relay wire harness and pin 104 of the ECU. Please note that this is the KA ECU. If there is no continuity then you need to fix this broken wire.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
Relay harness check
Turn the ignition to ON. Check pin 2 and pin 3 of the harness individually for current. Ignition power should be delivered to these 2 pins when the key is turned to on. If ignition power is not present in both of these wires, track down the broken wires and fix them according to the schematic.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
Remaining items
If you still don't get power, track it to the fusebox and check the pin on the fuse pump fuse that supplies power.
If you still don't get power, you may have a faulty ignition switch or broken wire through the engine harness that runs under the front US-left driver side fender, as described above.
If all wires are intact then suspect the ignition switch and its wiring from the battery and the fusible link.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
Ignition switch failure is not that common, but could be possible, especially on cars that have been converted from auto to manual.
If all else fails, start tracing power from the battery and follow the circuit schematic. Go through the circuit one wire at a time and see how far power can be found. Look for the broken component and see if you can fix it.
This is a little complicated after looking through the obvious parts. Just be patient and learn how to read a wiring diagram. It'll also help if you learn a little about how electronics work.
Good luck!
This thread was started in an effort to address common fuel pump questions. Zilvia.net and the author not responsible for content or misuse.
Always maintain a fire extinguisher meant for gasoline on hand, and do not smoke.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Background
If you suspect that you fuel pump is malfunctioning, symptoms can include impossible to start and you have verified that you have spark, fuel starvation, inoperative fuel pump, etc. The purpose of this article is to restore your fuel pump system to OEM specfications.
Go to zeroyon.com and download a copy of the FSM for your year 240SX. I will cover the DOHC S13 in this article. SOHC and S14s are similar.
Go to autozone.com and read the information available there on repair information. Select your vehicle from the choices available and look in the repair info section. They provide some basic information as well as some diagnostic and repair guidelines.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tools
* Multimeter - a good, high quality multimeter tool should be used to diagnose electrical problems. You can get one from any electrical supply store. I will not cover how to use a multimeter. Follow the instructions on the package or search google for directions.
* Screwdrivers and sockets - to remove trim panels.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
System Description
Look at the following picture for general system description. It's self-explantory.
http://img149.imageshack.us/img149/4867/fuelpump1gu2.jpg (http://imageshack.us)
The fuel pump itself is located in the fuel tank. There is an access panel located in the trunk compartment, near the US-right passenger side. This is where the blue fuel pump harness will be.
http://img365.imageshack.us/img365/7504/fuelpump2xt9.jpg (http://imageshack.us)
Let's walk through how the stock fuel pump control system works.
http://img365.imageshack.us/img365/9202/fuelpump3od6.jpg (http://imageshack.us)
1. Battery power is supplied via the E22 harness at the positive battery terminal.
2. Power passes through the fusible link located in Relay Box A located near the battery.
3. Power then travels to the ignition switch. When the ignition switch is turned to the ON position, power travels to the 15A fuse located in Relay Box A.
4. Power then travels to the fuel pump relay, also located in Relay Box A.
5. The fuel pump relay has 4 pins. 2 pins are connected to ignition power as described in #4. One pin goes to the ECU. One pin goes to the fuel pump itself.
When ignition power is available, the ECU can activate and deactivate the fuel pump. The fuel pump relay is normally open, i.e. no current flows to the fuel pump under normal conditions. To activate the fuel pump, the ECU draws current through the relay and the relay lets power flow to the fuel pump.
6. Fuel pump relay connection travels to the ECU through the firewall and to the ECU harness.
7. Fuel pump power travels to the fuel pump via the Super Multiple Junction (SMJ) located in the US-left driver side kick panel. It then travels via the body harness to the back of the trunk compartment.
Here are pictures of the locations of the various components.
http://img178.imageshack.us/img178/2530/fuelpump4rx2.jpg (http://imageshack.us)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preliminary Check
http://img365.imageshack.us/img365/4450/fuelpump5tw3.jpg (http://imageshack.us)
Have someone turn the ignition to ON. Listen for a faint, high-pitch noise as the fuel pump primes for several seconds. If you hear it, your fuel pump is getting power. If you continue to have problems, suspect a faulty fuel pump that is unable to maintain pressure or you have a leak somewhere in the fuel system.
Check your fusible link and fuse pump fuse. Inspect and replace as necessary. Sometimes a fuse can appear intact, but is in fact blown. Use your multimeter and measure for continuity between the two terminals of the fuse. If continuity doesn't exist, replace the fuse.
Check your fuse pump relay. Remove the relay. When you look at the pins of the relay, each pin is labeled with a number. Use a paper clip and jumper the 1 and 3 terminal on the wiring. If your fuel pump comes on with ignition, you have a bad relay.
Check the engine harness that runs under the US-left driver side front fender. This is common on 240SXs that has been lowered. The best way is to reroute this harness to the engine bay to avoid problems.
This is my friend and fellow Zilvia poster holding the harness.
http://g6civcx.angryhosting.com/S13/Tech/Harness.JPG
You should relocate this harness to the engine bay like so.
http://g6civcx.angryhosting.com/S13/Tech/harness2.JPG
These are the most common points of failure. Check them thoroughly. If you can't find anything, you will have to track down broken wires.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fuel pump check
Turn the ignition off and go to the trunk compartment. We will be working around this area to see if the fuel pump is getting power. PLEASE MAKE SURE YOU DO NOT SMELL FUEL. If you do, fix it immediately. Working with your multimeter may expose some sparks. Make sure you do not smell fuel.
For information about the fuel pump, including how to change it, read this article: http://www.zilvia.net/f/showthread.php?t=94575
Credits to the author for his contributions. This is him holding the fuel pump. You will be looking for that blue harness.
http://img.photobucket.com/albums/v317/bjorkluv/IMG_1921.jpg
Go find that blue harness and disconnect it. We will be working with the side on the fuel pump. Use your multimeter and check for continuity between the two wires going to the fuel pump. This harness is labeled 'C' in the circuit schematic.
What you're looking for is broken wiring somewhere in the fuel pump itself. If you do not get continuity, make sure you're checking the correct wires. If there's still no continuity, there is a broken wire or the fuel pump itself is defective. You can use bjorkluv's writeup to remove the fuel pump and repair, or look at the wires for damage.
If the fuel pump has continuity, we will go to the harness on the side of the body harness. We will be checking for power and ground.
http://img515.imageshack.us/img515/8689/fuelpump6zu3.jpg (http://imageshack.us)
Start by checking for continuity between terminal a and body ground. This is see if your ground wire is good. If you don't have continuity, follow the ground wire and repair the broken wire.
Now check for continuity between terminal c and pin 3 of the fuel pump relay. This checks to see if the wire described in #7 above is not broken. You will need a long wire to connect these 2 terminals. If you have no continuity, track down the broken wire and fix it.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
ECU check
http://img515.imageshack.us/img515/8689/fuelpump6zu3.jpg (http://imageshack.us)
Check for continuity between pin 2 of the fuel pump relay wire harness and pin 104 of the ECU. Please note that this is the KA ECU. If there is no continuity then you need to fix this broken wire.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
Relay harness check
Turn the ignition to ON. Check pin 2 and pin 3 of the harness individually for current. Ignition power should be delivered to these 2 pins when the key is turned to on. If ignition power is not present in both of these wires, track down the broken wires and fix them according to the schematic.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
Remaining items
If you still don't get power, track it to the fusebox and check the pin on the fuse pump fuse that supplies power.
If you still don't get power, you may have a faulty ignition switch or broken wire through the engine harness that runs under the front US-left driver side fender, as described above.
If all wires are intact then suspect the ignition switch and its wiring from the battery and the fusible link.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~
Ignition switch failure is not that common, but could be possible, especially on cars that have been converted from auto to manual.
If all else fails, start tracing power from the battery and follow the circuit schematic. Go through the circuit one wire at a time and see how far power can be found. Look for the broken component and see if you can fix it.
This is a little complicated after looking through the obvious parts. Just be patient and learn how to read a wiring diagram. It'll also help if you learn a little about how electronics work.
Good luck!