Fuel Pump

FORD VEHICLES HAVE A PROBLEM WITH THEIR FUEL PUMPS!

ALL Ford fuel-injected motors (which I believe is all motors since 1991) have an in-tank fuel pump that is a disaster on HF.  Guaranteed to radiate S5 on 10m to S9+who cares anymore on 40m and down.  Fortunately Ford recognizes this and makes an electrical filter that seems to work 90% of the time (I don't know why 10% don't, but some Usenet searching shows some failures-to-fix).  The Technical Service Bulletin (TSB) is 98-7-3.  The filter install requires dropping the fuel tank, so unless you're a gearhead too take it to the dealer to have it done.  In-warranty vehicles only have to pony for the part, no labor.

The test for fuel pump noise:  turn on the ignition BUT don't start the engine.  Listen in your radio.  If you hear noise when you turn the key to "ON" that lasts for a second or two, then quits, it's the fuel pump.  If not, LUCKY YOU!!

Ignition System

I guess I might be a failure-to-fix; in November 1999 I got the fuel pump filter installed (though quite frankly I am not 100% certain the dealer actually installed any hardware) with no effect.  One interesting thing about the 1999 F-150 is that it is a distributed low-voltage ignition system.  There is no coil/distributor setup, but rather each cylinder has its own coil pack right on top (at least on the V-8's...the V-6's have one coil pack per cylinder pair).  This has the advantage of the system being +12VDC all the way up to the spark plug (practically); there is no pont in changing high-voltage spark plug wires or distributor caps/points/rotors because there are none!

One nice thing to see also is that Ford has a "Radio Interference Capacitor" for both sides of all engines (one for each row of three or four cylinders) shunting the coil packs to the engine block.  This is factory standard installed equipment (I'll put a picture of it here soon).

NOTE I got curious one day and took one of the Radio Interference Capacitors off the block and onto my Boonton 160-A Q-meter (with standard inductances) to measure its impedance at RF.  I'm happy to report that the parts RF impedance is <2 ohms from 3-30 MHz.

I have several theories on what to try:

1. I've read on the Usenet that some have had ignition noise problems with split-fire spark plugs.  I don't know what mine are but I'm told that almost all recent engines use them.  Could be that swapping out for conventional plugs will help.
2. As noted in "Electrical Installation", the engine block (actually head)-chassis and battery-chassis grounds are substandard.  The engine block ground is only a 1/4" piece of braid; I sincerely doubt that's worth much at HF.  I plan on replacing it soon with some copper strap.  The battery ground is 10AWG; and although that sounds good, an oft-repeated National Electric Code rule is "ground wires should be at least as large as the largest primary wire".  So I will replace this with 4AWG (the size of my primary wire) soon as well.
3. I have jumpered my exhaust pipe to the chassis at four points along the underside with a small improvement noted.
4. Measurements with my VX-5R probing the vehicle seem to indicate that the electrical wiring system propagates the noise very well.  Holding the antenna of the VX-5R near the driver's airbag, dome light, and trailer wiring socket generates S9++ noise.  The noise is very localized to these locations.
5. Measurements with my oscilloscope show the noise is RPM-sensitive in both period and amplitude

Two gotta-have instruments to assess and measure your noise with:

1. Good old oscilloscope.  Doesn't have to be too fast (my Tek 485 definitely not put to the test here!).  Put your radio in AM mode (no filters, widest possible selectivity) and pipe the audio out to the 'scope.  Rev the engine, etc., and observe the waveform amplitude and period.  I will post some pictures of my 'scope waveforms soon.
2. I just thought of this one today...a computer with sound card!  Really, there are some really good Audio Spectrum Analyzer applications available for sound cards.  Why not pipe your AM-demodulated audio right into the sound card and look at the spectrum?  If there's an RPM dependence you can relate it to frequency.  An added plus might be if you have multiple sources you're tracking down and you can separate them in frequency (maybe one whose frequency changes with engine RPM and one that doesn't).  I haven't tried it yet but I will soon.

I have read conflicting information on how grounding the radio chassis to the vehicle affects noise pickup.  Some swear by it and some swear at it.  I suppose the best course is to try both and see how it impacts your installation.  In my case, there was a noticable difference (reduction) in noise pickup with the radio grounded to chassis than without, so I stuck with it.

Did several experiments/measurements on the truck this summer.

The most interesting one was recording my received noise on a laptop w/ soundcard and analyzing the files with a soundcard-based audio spectrum analyzer.  There are several good free- and share-ware audio spectrum analysis programs available; I used <name of program here>.  To make a long story short, I can look at the spectrogram of the recorded audio and tell you the RPM of my engine...so it's definitely an ignition-related issue.

The recorded files are pretty large but I'll put them here soon.

In addition to measurement, I actually did some hardware work:

• Swapped out the OEM battery (-) and engine header to chassis grounds, replaced them with 4AWG wires of roughly the same length.  No change noted.
• Moved the radio to the front of the cab (no remote kit), no change.
• Took off the copper strap jumper between cab and bed and reconnected it bed to frame; noise definitely worsened.
• Reworked OEM cab-frame grounds (one on driver's side, two on passenger side) by removing straps, grinding/sanding connection points to bare metal (which they were not to start), applying Cu-No-Ox, and reinstalling.  No change.
• (2000-10-01) Did some simple ARRL handbook calculating and found that most of the ground straps I've been using, at 12"x1", are dead before they started...a 12"x1" strap is like 40 ohms of reactance at 28MHz.  This is not ground (meaning...minimum impedance bonds to reduce induced voltage drops)!  So I reworked the underneath and made three new ground connections using only 3" of strap (6.3 ohms @ 28MHz).  I placed them at:
• Rear of bed to frame, driver's side (so very near the HS-1500 mount)
• Front of bed to frame, driver's side
• Rear of cab to frame, driver's side

• Passenger side as before
• Front of cab to frame, both sides.
• Engine block to frame
• Bumper to frame (bumper is metal, and just bolted on to the frame ends, no doubt painted surfaces).

In my readings I have seen different parties state that (braid/strap) is better for grounding at RF.  Well the Q-meter needs more work so let's check it out.
Measurement samples:  13" long pieces of 1" wide braid, 4AWG wire, and 1" wide Cu strap at 28 MHz.

• 4AWG         193pF to resonate     170nH        30 ohms        Q=100
• braid            273pF to resonate    120nH        20 ohms        Q=100
• strap            210pF to resonate    150nH        25 ohms        Q=150