Fuel Pump Whine

[BIGHOG]

I have been battling this for a long time. Here goes. So today I finally decided to build the "filter" to install inline with the fuel pump on my 99 s10 ZR2. Had some RS ferrites in the garage so I gave it a shot. I took 3' of 14awg and wrapped it around 4 of the ferrites as desribed in various other posts. Here is where I got some new info. Before pulling the truck into the garage I bend the 108'' MJF SS whip over and stick it into the stake pocket of the truck. It is mounted on a 1/4'' thick steel mount that I made and then bolted to the toolbox. Yes, the toolbox is bonded to the bed. I place the new "filter/choke" inline, solder it up all nice, shrink wrap it, mount it, done. I walk over and cycle the pump. Amazing!!!!!!!!!!!!!!!!!! No more pump whine. Now keep in mind that the ant. is still in the stake pocket of the bed at this time. I am really stoked at this point. Even made some phone calls to tell how this magic fix worked out. So I then back the truck out of the garage, stand the ant. back up tall and fire up the old GL to do some talking. And bam, pump whine is back! I played with it a little and found that if I grab the ant. and start to bend the tip towards the ground, at around cab high the whine I completely gone. As I let the ant. back up the whine comes back. This same thing happens if I pull the ant. to the drivers side, pass. side, front, rear. I have the truck bonded with braid very well all over, exhaust to. All the power and groung for the GL and the DM all go directly to the bat. with nice fine strand wire and soldered ends. Fire away gentlemen!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

['Doc]

How hard would it be for you to drop the gas tank to get to the power leads from the fuel pump, AT, the pump?
- 'Doc

[BIGHOG]

It would be a little easier to lift the bed enough to get to the pump. Watcha have in mind? Oh, and what is the theory behind the whine going away with ant. position?

['Doc]

First the antenna bending over thing. That really doesn't tell you anything. When it was stuck in the stake pocket, you basically had a shorted out antenna, or same as grounding the center conductor of the coax. Not going to hear much of anything that way, whine, signals, whatever. The same thing, but to a lesser degree when you had a hold on the antenna and were bending it, you were providing a path for the signal to go to ground through you to whatever you happen to be standing on (dirt) or touching (truck), etc. Sort of like not having an antenna.

The factory 'fix' for a noisy fuel pump is a capacitor across the (+) and (-) of the fuel pump as close to the fuel pump as possible. Where that power line leave the tank is the best place. The further away from that pump you get, the more of that power line is acting as an antenna to radiate the noise. So, the shortest 'antenna', least amount of power line between pump and capacitor is good. Putting that ferrite 'choke' after that capacitor amounts to a filter just like on a power supply, give that noise a path to ground rather than into the rest of the wiring. What size capacitor? I don't know what GM recommends. But, something about 0.1 or 0.01 uf and at least 50 volts ought to do it. I'd use a ceramic disc capacitor, not a polarized one. A polarized one will work, but make sure the polarization is correct!! You might ask your local Chevy service dept. what the factory fix is (capacitor size). (They know, but getting them to tell you sometimes is a real trick!) That's got to be a fairly 'standard' thing by now, it ought to be on the internet somewhere. If one capacitor doesn't quiet it down enough, add another one, or two.

One thing about those ferrite chokes is that the more wire you can get on them the better it works. So does using several of them instead of just one of those ferrite core thingys.

If doing that doesn't get rid of at least -some- of the noise... sell the @#$ thing.
- 'Doc

[BIGHOG]

Thanks doc. I am starting the search for the cap size on the net right now. I will be making the trip to RS today to pick up a couple of caps if I can find the info. What do you think about shielding in the coax from the ant. to the DM. I am running Belden RG8 (it has a clear outer layer and you can see the silver shielding). It is not high dollar stuff, but it has gotten me by for a while. The order to a local shop is already been placed. I am picking up my new Belden 9913 on Mon. Just curious about the shielding qualities of the 8 vs the 9913. Loss, shielding, interference, etc. I guess some of it is personnel opinion too! And I just want to say to everyone on the forum. THANKS THANKS THANKS. The bug has hit me like a tone of bricks since I found this site. Everything I know about radios is from this sight. I tell anyone with questions that I can't answer to log on and get ready to learn. Some mighty fine people on here. Just wanted to give some credit where credit is do. My wife is starting to get jealous of the computer, and my GL hahaha.

['Doc]

I'm glad you mentioned personal opinion in that coax question!! I do have opinions about coax and they aren't always the same as most people's.
'9913' versus some other kind of coax. In general, 9913 is some pretty good coax. It is harder to work with than the 'soft' coax is, and has at least 1 other qwerk that is bothersome. Since it's hollow inside, it really is a water hose. One of the 'second' things you learn about 9913 is to seal the ends so water/moisture can't get into it. You haven't lived until you find a radio sitting in a puddle of water on your desk.
If the shielding on coax is close to 97% you have some good coax. More would be nice, but certainly not an absolute necessity. If something like 97% won't 'do it', you are in a very noisy RF environment and will have problems with any coax, even hard line. A very great amount of the 'worth' of coax deals with the frequency of use. The higher you go in frequency, the better the coax you have can really make a big difference. That frequency thingy isn't talking about Mhz, but in HF, VHF, UHF, SHF and whatever comes after that. When dealing with HF stuff, almost anything will work reasonably well. Lot's of 'fudge factor' in that last statement! But, it's generally true anyway. The idea is to use something that has the right impedance, isn't too 'lossy', will handle the amount of power you think you will put through it, and still 'fits' your wallet. (I'd add in 'easy to work with' but that would mean not counting 9913. ) Anything after that is just icing on the cake, may 'taste' good, look pretty, but all it's gonna do is make you fat('er), doesn't contribute anything practical.
I've never run across a situation where having anything 'better' than RG-8 was required for HF stuff. That assumes that RG-8 was of good quality, of course! If you will do some 'in-depth' checking, I think you will find that some types of the 'better' coax have less abilities than some of the 'lesser' types of coax. Power handling ability is the first that comes to mind (and that particularly includes 'hard-line').
I think that's a bit more/different than what you were wanting/expecting to hear, so I'll quit. What do I think about your using 9913? I think it'll probably work just dandy. Little bit of 'over-kill', but shouldn't hurt anything at all. Oh, are you gonna have fun working with that @#$&!
- 'Doc

(Don't worry about the shielding on the coax, shield that @#$ fuel pump power line!)
(And before you start thinking about that... just use the cap and choke. Can you imagine running a shielded power line from the gas tank to where ever it goes??)

[BIGHOG]

Long weekend........... Got caught up my chores so I decided to dive in. Lifted the bed and soldered in two .01uf 500v caps. No change in the fuel pump whine. Picked up my 9913 jumpers and installed them. No change. I talked to an engineer at work and he added that I should solder in one more cap (1000uf) Reasoning is to filter out more than one frequency, and something to do with the type of motor and a bunch of other technical lingo that he lost me on. I am going to try a different routing of the coax and see if that helps. I am also wondering about the placement of the whip.

['Doc]

It really isn't as likely, but since you have started on the capacitor thing, why not place one across the power line to the radio? From what I've found listening to others talk about the fuel pump noise, it's a radiation type thing rather than a conduction type thing (gets in through the antenna rather than the power line, as you seem to have discovered). But, why not do the by-passing on the radio's power line too, can't hurt. (It's another one of those things where the closer you get it to the radio, the better.) Your engineer friend is right, the noise isn't just one frequency, probably several, so bigger is better to some extent on those capacitors (the capacitance, not the voltage). That 500 volts is more than enough. That high voltage thingy is to protect against possible voltage spikes, so something between 2 to 10 times the voltage normally applied (12 volts in this case) is typically plenty.
And since you seem to have gotten all your 'honey-do's caught up, what else could you possibly have to do? Right?
- 'Doc

[BIGHOG]

Excellent idea doc. Who knows what king of nasties might be coming in through the radio power cables! I will keep trying till I get this thing nailed. I know the fix is there somewhere. Just gonna keep plugin' along.

[Century21]

Hey doc is a .01uf 500v a ceramic disc capacitor? wouldnt a electrolytic be the choice?

['Doc]

Is a .01uf 500v capacitor a ceramic disc capacitor? I don't think so, at least I've never seen one with that high of a voltage rating, but I'm sure I haven't seen them all either. Would an electrolytic capacitor be better? I don't think so. Why would it unless you needed that voltage capacity? A ceramic disk is more weather proof than the typical electrolytic capacitor, that's something to think about too, I think. Not a huge 'biggy', but something to consider.
- 'Doc

[721HACKSAW]

I had the fuel pump whine in my Ford Ranger. I unhooked my coax to be sure the noise was coming thru the antenna and not the power supply wires. I used ferrite cores at the fuel pump power wires, this seemed to help the best. The noise is not completly gone but is now tolerable.

[Century21]

Ok cool.. I know back in 96 my buds radio was getting some bad whining noise. We used a 16v electrolytic. The biggest on RS sold. And put it in a plastic box and ran his power wires through it going to the radio. It surpressed the noise very well.

[BIGHOG]

I am really fed up with this thing. Pulled the bed and soldered in the caps. Put it all back together an no change. I also wedged a ground strap inbetween the tank(on bare metal) and the steel strap the holds the tank up then to the frame. This also resulted in no change. I changed the whip out to a mag w1000 and ran the coax through the door just to see what would happen and the whine went away. I then re routed the 9913 (which is running the 108) as far to the pass. side of the truck as I could(tank is on drivers side) but this did not help. I am stumped for the moment. The test with the mag 1000 shows me that if i was to run a puck mount on top of the cab and kept the coax from running under the truck then I could eliminate the whine. But, I really dont want to lose the 108! Any other ideas guys?

['Doc]

maybe it's time to sort of stand back and take a look at the whole thing again. Not that I think you're wrong, but are you sure it's the fuel pump making the interference? Eeuuw, nasty thought if it hasn't been the culprit.
Did ANY of the 'fixes' make ANY difference at all? I'm surprised that the 'cap-n-coil' thingy didn't make -some- difference, really. If it did, then it's a matter of adding another 'stage' or two, just like a power supply.
From there I don't know what else to tell you. Swap the @#$ truck? Don't give up. It's probably something small that's just being over looked... maybe
- 'Doc

[BIGHOG]

Thanks for the words of comfort Doc . But, yes. I am sure it is the fuel pump. The whine will come into play with a cold engine ignition cylcle (prime the fuel rails 2-5 secs.). Then a constant while as the pump runs. Then another deayed shut-off after the ignition kill. Also verified by the tell tale RG8 SNIFFER. And I too am suprised that the "cap&coil thing" did not work. No change at all. The only change was the mag mount on top. I still do not know if the change was based on coax routing, or, the ant. itself picking up the whine. This really has me stumped. I am thinking about getting down to bare bones and trying the ol' foil trick just to see what happens. I am wondering really hard if a puck mount on top with all coax staying inside the cab might solve the issue. I have lived with this problem for years and finally decided to hunt it down. I have really opened Pandora's box on this one!

[BIGHOG]

Any other opinions on moving the 108 to the top of the cab, and running the coax inside the truck?