One of the main RFI radiators in the Ford Sport Trac variable voltage
ignition system is the primary wiring. Ford and probably most other
manufacturers run all the primary wiring in one harness. The 12 VDC
wires that feed power to the controller that drives the ignition coils
sees significant RF pulses from the controller which are then radiated
in what is a large loop (sort of like a ground loop). Part of the
problem is that the low voltage + wire is run all over the engine with
no adjancent negative wire which allows for no possibility for balanced
line which would attentuate RFI.
The solution for the Ford is the run a dedicated low voltage line from
the fuse panel to the controller. Using Marine low voltage wire (+/-)
cable solves the low voltage wire RFI.
In the case of the Ford it uses an igniter with spark wires. The
secondard wires are shielded with 1" silver tinned braid. The engine is
so quiet now that I can hear the sensor clicking on the ABS system but I
can also hear the low power AM radio used for parking at National
Airport some ten miles away.
The gas tank noise is solved with a corcom AC line filter mounted as
close to the tank as possible. In the Ford the filter is actually
mounted inside the gas tank (a warrantee repair or $350 after
warrantee). If you mount the external filter be sure to bond the metal
case to the frame rails.
Good Luck,
dave
wa3gin
Ford Peterson wrote:
Man does this sound like Deja Vu or what? I have a Tundra with the 4.7ltr V8, but the problems may be common.
I found that the biggest source of noise was coming from the COPs (coil on plug). But you may not have these on your 4 cyl. This is the Lexus 32 valve V8. I have no clue if there is a common pedigree or not. It's easy to identify since the noise follows the RPM of the motor.
The second noise, and perhaps worse on 40m and 20m than 17m, was the electric fuel pump. The pump wires go from the fuel tank, up to the cab and come up right under the driver's side seat, under the floor carpet to the driver's kick plate by your left foot. It was noticable if the engine was NOT running, but only for a second or two while the fuel system pumped up. Once the system was up to pressure, the pump shuts down. It runs continuously with the engine running. It also changes pitch based on fuel consumption. At highway speeds, the noise is considerably less than at idle--and the pitch was different. Pulling the fuse on the pump (or was it the relay?), I was able to eliminate the noise 100%, but of course the engine would quit in about 3 seconds.
The "fix" is a nasty kludge job if you need to go into the harness and insert some sort of filter. What I found is that dressing the feedline away from the area where the fuel pump wires run as far as possible. I have not completely eliminated my noise, but it is at or below S0 on my IC706MKIIG (previously S9). The remaining whine can be eliminated with the NB on the ICOM.
I would NOT continue probing with a ground strap on those sensor lines. You blow the engine controller on that Toyota and you are talking about a $1200 repair. No joke. DO NOT PROBE with either power or ground! Do NOT mess with the control lines unless you know exactly what you are doing. I have the schematic on my truck and it only shows the harness connections, not the internal electronics to the modules, so you have no clue what measures the factory made to prevent damage from probing short circuits around.
Note that with the antenna removed from the connector (I use a hamstick) the noise could not be heard. It is radiated noise so the mounting location may matter. I was able to move my antenna from the middle driver's side stake pocket to the passenger's rear stake pocket, dressing the lines to run under the lip of the box. That seemed to be best but not perfect.
Good luck...
Ford-N0FP
ford@cmgate.com
----- Original Message -----
From: "john heinrich" <nd6h@sbcglobal.net>
To: <rfi@contesting.com>
Sent: Wednesday, January 19, 2005 6:40 PM
Subject: [RFI] RFI From 2003 Toyota Tacoma
I have a 2003 Toyota Tacoma SR 5 Extra Cab truck with a 2.4 ltr 4 cyl. I have an Icom 706MK2G in the truck and the antenna is a tarheel 100 mounted on the driverside rear in a fold over hitch mount. The Antenna mount attaches to the rear of the frame rail. I have a ground strap going to the antenna. I have tied all the body panels together. I am getting static on 20 and 17 meters when the engine is running.( I think it is presant on all the bands bellow 20 meters as well, but due to the level of static usually presant on these bands I am not possitive) 15, 12 and 10 meters are not effectedThe signal strength is s5 to s7 and does not change when the engine rpm is increased with the gas pedal. When the Idle speed is kicked up via the engine control computer there is a slight change in the static. I have a good ground on the radio. The interferance stops when I disconnect the coax from the antenna. I have tried tracing the source of the interferance using an RFI sniffer and
I h
ave
found several different locations, and I think the source location is the
engine control computer. I am now trying to find a way to trace the exact wire
or wires broadcasting the interferance. I am also not sure how to eliminate
the problem once I locate the source wires.
I was able to stop the interferance once when I tried grounding the airflow sencing module. The Check engine light also came on due to the ground. I believe this temporarily shut off the computer. I turned off the engine and waited a few minutes after ungrounding the sensor and then started the engine again. the check engine light was now off and the interferance was back.
Any suggestions would be greatly appreciated.
John ND6H
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