I have seen a number of posts in the past where people have a screeching
noise across all HF when their Toyota trucks (including my 2002 4-Runner)
are running but not when the key is ON.... that is likely the fuel pump....
unlike other vehicles, the fuel pump comes up so fast that you don't hear it
unless there is a constant need for fuel.... if you shut off the engine and
then try to hear the pump in the ON position, you won't hear it... the fuel
system pressure is still high enough.... I let the truck sit for 2 days and
turned the key to ON without starting it, and the pump noise lasted maybe a
second then quit... of course, with the engine running it is there all the
time....
Toyota fuel pumpnoise is tough to remov, and there is no servce bulleting
covering any Toyota pump RFI noise.... the fuel pump is accessed from below
the passenger seat, but there are a LOT of wires coming up through the floor
from the gas tank....all carry the RFI to some extent.... the 12 volt wires
to the pump carry most of the noise... a common mode choke and 4 clamp-on
ferrites re3duced it from 40 dB over S9 to just S9, and adding any value of
capacitor either before or after the choke only increases the noise... but
it's still the worst of the 3 noise sources I found... any hints for the
Toyota?
The other two RFI sources are A/C fan (worst at high speed, not noticeable
on low speed) and the ignition.... a sniffer shows the plug wires to be
major noise contributors (S9 on 40 meters).... foil wrapping the three long
plug wires as well as the three coil-on-plug units seems to reduce ignition
noise a lot.... next step is to install braid and screen enclosures.
Any other hints for solving late model Toyota HF RFI? It's almost time to
get the mobile ready for OH and IL QSO parties.
Thanks
Mel KJ9C
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