Nissan Fuel Pump RFI

I wanted to post this somewhere on the Internet so some poor Ham like me has a chance of finding it.  I looked all over the place for information on how to correct this problem and found it in six different places.  I have combined the knowledge into one article.

I have a 2003 Nissan Pathfinder and installed an HF radio in it. On 75meters I was getting a loud "hash" noise with the engine running. Some research indicated that Nissan has fuel pumps notorious for producing RFI. If you are having similar problems you can test by tuning your radio to 75meters and just turning the key on PAST ACC like you were going to start the engine. The fuel pump will run for about 1.5 seconds and you should hear a burst of noise that lasts that amount of time... If you hear that, read on.
 

The good news is the problem is EASY to fix by placing a bypass capacitor across the fuel pump motor wires.  The fuel pump is located on top of the fuel tank and is accessible by simply folding the passenger side back seat bottom forward. There is a cover plate there with wires going into it and four Phillips screws holding it on. Remove the cover and you will see two electrical connectors, one with two large wires and the other with three small wires. The one with two large wires is the fuel pump power connector.

REMOVE THE KEY AND PUT IT IN YOUR POCKET. Remove the battery cable. You are fooling with electricity on top of a gasoline tank! BE CAREFUL!
 

Remove the connector with the two large wires on it. Take a .01 or .015 microfarad capacitor rated at 1000 Volts and carefully work the leads down alongside the wires until they stick out of each connector inside the plug. Let me make it clear that you are wanting to place the capacitor in circuit across the two wires. Stick one of the cap. leads down one side and the other lead down the other side. Stick it so far through that you can see the ends of the leads in the bottom of the plug. Bend the ends over and trim them so that they cannot short together and will not pull out of the plug. If you have done it right the base of the capacitor is now flush with the back of the plug and each lead is making contact with one wire.

USE A 500 Volt CAPACITOR minimum, a 1000V is better! The ring back voltage from the DC motor can be very high which is what is producing the RFI in the first place. DO NOT USE A 50 VOLT CAPACITOR. Capacitors often fail by shorting especially when they are exposed to high voltages. You do not want a short over your gas tank!

Replace the plug, reconnect the power and test your radio as described above. If you have done it right your RF hash will be gone.

This may work on other DC motors and on other vehicles. Locate the capacitor as close to the motor as possible and always use a high voltage cap.

Question / Comment: Email me

THE ABOVE PROCEDURE FOR CURING RFI PROBLEMS ON NISSAN FUEL SYSTEMS SHOULD BE DONE AT YOUR OWN RISK.  THE AUTHOR,  THIS WEBSITE, NOR THE WEB HOST ASSUMES ANY RESPONSIBILITY FOR THE SAFETY OR ACCURACY OF THIS PROCEDURE.  THERE IS NO WARRANTY EITHER EXPRESSED OR IMPLIED THAT THIS PROCEDURE IS SAFE AND NO LIABILITY WILL BE BORNE BY ANY PARTY INVOLVED IN PREPARING OR PUBLISHING THIS DOCUMENT.  THIS PROCEDURE MAY VOID YOUR MANUFACTURER'S WARRANTY AND YOU SHOULD CHECK WITH YOUR CAR DEALER OR MANUFACTURER BEFORE PERFORMING THIS MODIFICATION.  IF YOU ARE A "KLUTZ" OR ARE UNSURE OF EXACTLY HOW TO PERFORM THIS MODIFICATION TAKE THE VEHICLE TO YOUR DEALER OR OTHER QUALIFIED TECHNICIAN.

USE AT YOUR OWN RISK!