[RFI] 4 Runner Fuel Pump

wng@daimlerchrysler.com wng@daimlerchrysler.com
Wed, 9 Oct 2002 13:15:12 -0400


In the fuel pump configuration, most of the noise generated by the pump
motor is converted to common mode by capacitive coupling to the motor
housing, if it is not grounded to body sheetmetal (usually the case with
modern thermoplastic tanks) and to the gauge sender lines.  The best
solution is a COMMON MODE choke in the motor pair and in the gauge sender
pair.  All four lines should be bypassed on the vehicle (not tank) side
with 0.05uF capacitors connected by a low impedance (i.e.: SHORT, FAT)
braid, with a large area connection to body sheetmetal.  All of this should
be as close to the tank/pump assembly as possible (There may be an access
plate under the carpet in some vehicles.)

An appropriate common mode choke may be constructed by winding six or eight
turns of twisted pair of appropriate gauge wire on a large cross-section
area #43 core (14 or 16 AWG for the pump,18 or 20 AWG for the gauge).  Be
sure to use wire with fuel resistant insulation (e.g.: crosslinked
polyethylene).  Make splices by using a crimp sleeve AND soldering,
followed by duplex heat shrink (meltable sealant interior).

Bill Gilmore WB8FPQ
EMC Technical Lead
Dodge Truck Electrical/Electronic Engineering

                      Dennis Vernacchia                                                                                             
                      <n6ki@juno.com>          To:       rfi@contesting.com                                                         
                      Sent by:                 cc:       SWTraffic@Cox.Net, w1rfi@arrl.net, rdavis@abac.com, n6ki@aol.com           
                      rfi-admin@contest        Subject:  [RFI] 4  Runner Fuel Pump                                                  
                      10/09/02 01:29 AM                                                                                             

Has anyone been successful in quieting down the noise from the
electric fuel pump in early 90s Toyota 4 Runners

I tried different mix beads including 43 and various ceramic caps to
ground from
each lead close to the pump.....no effect

I know it is teh pump as with engine running I disconnect it and before
engine stalls noise level goes from S7 to S1

I also tried outiing a 250 uH choke in each lead and also caps to ground
on either side of choke and all I can do is INCREASE noise (hash) to S9
when caps are on far side of choke away from pump.

Values used were 0.002uf, 0.01uf and 0.05pF

We will try a same value caps directly across the pump leads as close
to pump as we can get which is 3 or 4 inches awauy from pump at connector
in wire harness

Any other ideas appreciated....no, we are not going to drop the tank!

73, Dennis n6KI

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