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Fuel pump noise in Jeep.

hacksaw

hacksaw

Active Member
Jan 25, 2009
191
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This question is to moleculo, but others are welcome as help is needed. I have a 03 Jeep TJ Wrangler SE. I think I have bad fuel pump noise. I have added a Tram alternator filter, as well as an inline noise filter on the radio power wire. I also have added various grounds to the vehicle. When the radio is on, and engine off, it is quiet. As soon as I turn the key on, I hear a short static sound when the fuel pump kicks on, and then a constant static sound when the engine is running. I read where moleculo had this problem in his Jeep. What to do??? Thanks

Shawn
 

I was able to get at the fuel pump wire harness on my 99' TJ and unplug it without having to drop the tank, but it was quite a challenge. It probably would have been a lot quicker to just drop the tank...it's only a few bolts and if you have a floor jack, it's easy to do.

What I did is to peel some of the wiring harness jacket back to expose the wires so I could identify the positive and negative wires (use a VOM meter if you have to). On my tech bench, I made up a filter by taking some red & black wire and wrapping it around a ferrite torroid as many times as a could. I then used a couple of .01uf ceramic disk capacitors and soldered them across the positive & negative wire. Then I got under the jeep, cut the positive and negative (ground) wire going to the fuel pump and spliced the filter inline. To keep it neat, I I heat shrinked the whole thing before plugging the harness back into the fuel pump. This got rid of the fuel pump noise for me.
 
moleculo said:
I was able to get at the fuel pump wire harness on my 99' TJ and unplug it without having to drop the tank, but it was quite a challenge. It probably would have been a lot quicker to just drop the tank...it's only a few bolts and if you have a floor jack, it's easy to do.

What I did is to peel some of the wiring harness jacket back to expose the wires so I could identify the positive and negative wires (use a VOM meter if you have to). On my tech bench, I made up a filter by taking some red & black wire and wrapping it around a ferrite torroid as many times as a could. I then used a couple of .01uf ceramic disk capacitors and soldered them across the positive & negative wire. Then I got under the jeep, cut the positive and negative (ground) wire going to the fuel pump and spliced the filter inline. To keep it neat, I I heat shrinked the whole thing before plugging the harness back into the fuel pump. This got rid of the fuel pump noise for me.
Click to expand...
I have a couple of prebuilt rf noise filters. Should I install one inline close to the fuel pump? Its almost like the fuel pump is generating the noise into the antenna through the wire????? I do not know this for sure, but I guess it would about the same as the ferrites right?
 
It won't hurt to try...those pre-built noise filters are basically the same thing that I've described. However, the method I've described will result in a much smaller package and will also only cost you about $5. And you know it works (y)
 
I have a couple of round ferrites. One is about 1" long. Would that work to wrap the wire through? And are using one on the negative lead as well? I didn't think you were, but thought I'd check.
 
A different way of looking at it...
That choke works because you are putting inductance in the power line which stops alternating current, or pulses, which is what all 'noise' is composed of. The more inductance the better till the noise is stopped. Any more inductance is just 'extra', doesn't hurt, but really isn't necessary.
How you get the inductance is a matter of what you happen to have or can make to produce that amount of inductance. Winding a coil on ferrous metal (bolt/link/etc.), or a ferrite bar/cylinder/ring/etc, will certainly work. Very basically, the bigger the better till it's totally ridiculous. That typically means lots of turns around/through a ferrite core. Got a sort of 'small' ferrite core of some kind? It'll probably take more than just one. And remember, the wire used to do that winding has to be large enough to handle the current drawn by the fuel pump or whatever else you're trying to 'filter'.
The choke stops AC/noise from getting any further. A capacitor 'shunts' that AC/noise to ground. It's usually better to have 'too much' filtering than not enough. Ain't got enough with just one? Add another one, or two, or sixty of the @#$ things! It works.
- 'Doc
 
moleculo said:
On my tech bench, I made up a filter by taking some red & black wire and wrapping it around a ferrite torroid as many times as a could. I then used a couple of .01uf ceramic disk capacitors and soldered them across the positive & negative wire. Then I got under the jeep, cut the positive and negative (ground) wire going to the fuel pump and spliced the filter inline. To keep it neat, I I heat shrinked the whole thing before plugging the harness back into the fuel pump. This got rid of the fuel pump noise for me.
Click to expand...

I think I will make one of these. I have to drop the tank on my TJ to install a new skid plate. I might as well install one of these while I am at it, I also have the same noise in my TJ. Key off, I have very little to no static. Key on, the static is instantly back. Are there any special instuctions a not so technical guy like myself might need? I can source the parts at a local Radio Shack and I can solder, but i'm no electrical engineer by any means. Would a ferrite toroid like this work for this project?

Toroid Coil Assortment (10-Pack) - RadioShack.com

Do you have any pictures of the finished product?
 
BubbaDX said:
I think I will make one of these. I have to drop the tank on my TJ to install a new skid plate. I might as well install one of these while I am at it, I also have the same noise in my TJ. Key off, I have very little to no static. Key on, the static is instantly back. Are there any special instuctions a not so technical guy like myself might need? I can source the parts at a local Radio Shack and I can solder, but i'm no electrical engineer by any means. Would a ferrite toroid like this work for this project?

Toroid Coil Assortment (10-Pack) - RadioShack.com

Do you have any pictures of the finished product?
Click to expand...

I think what Doc and Moleculo pointed out, is that making a toroid with lotsa/extra winds might be overkill; but it is sure to extract all of the noise. These Radio Shack toroids might be 'toroids'; but not enough windings on them and may prove worthless for what you are trying to accomplish. Having pulled a few gas tanks out of vehicles in my day: I don't think that you want to do the same job twice. Especially if it means to remove the skid plate for a second time as well.

Moleculo's description of 'how to' shows that it is just that simple. You can make a toroid as he described. Then; take a picture of what you have made and load it on your computer and post it as an 'attachment' to your next post. This way, we can see what you've made and if it will be sufficient for the job - before you put it in. The capacitors are cheap and may be scavenged from old/broken electronic items that you might have.. If not; then they are extremely cheap to buy at Radio Shack. You can probably build this entire filter from scrap materia and scavenged parts - and not have to spend a cent! At worst; it might cost as much as ~$5 for two decent sized ferrites, wire, shrink wrap, and capacitors.

If it was me doing this job; I would also heat shrink wrap all of the work when it is done - as Mole did for his as well. Since we are talking about a Jeep; I suspect that puddle jumping is what you will do. The sealing of this home made filter should be considered a priority to your application.

Keep us posted!
 
How large of a toroid should I be looking for? We have a really cool electronics store about 20 minutes from my house called Gateway Electronics that puts Radio Shack to shame. I can hit them up and get all the components. I will post a picture before installing, because no I really don't want to drop the gas tank twice. In a TJ the tank is strapped to the skid plate, so atleast I can use a floor jack to lower and raise the tank. But I still want to shoot for 1 install. Water proofing will be a must. I don't like really deep mud, but sometimes its unavoidable, and i have been in water over my floorboards. Here is my webpage if you want to check out what I do with my Jeep.

Venemous Duck Racing
 
why couldnt a guy use a transformer hooked in line with a cap? A transformer is just a winding wrapped arround a ferrite core correct? DC transformer that is.
 
Why couldn't you use 'half' a transformer as that choke? The only reason you may not be able to do that is the size of the required wire making up those windings. Unless you're talking about a really, really big transformer, the windings will be too small of a size of wire. As a matter of fact, a '100 years ago', that's exactly what was used.
So what size wire and then how much of it? Don't know, so take a look at the power line going to the fuel pump, what size is it? I'd use one size larger, and then maybe 15 - 20 feet of wire to wind that choke. What size torroid or metal thingy to wrap it on? Beats me, big enough to hold that much wire. Double or triple layer it. Won't be as large as a transfer case, but it won't be the size of a 'AAA' battery either. There ought'a be somewhere under there to hide it, sort of.
- 'Doc
 
W5LZ said:
Why couldn't you use 'half' a transformer as that choke? The only reason you may not be able to do that is the size of the required wire making up those windings. Unless you're talking about a really, really big transformer, the windings will be too small of a size of wire. As a matter of fact, a '100 years ago', that's exactly what was used.
So what size wire and then how much of it? Don't know, so take a look at the power line going to the fuel pump, what size is it? I'd use one size larger, and then maybe 15 - 20 feet of wire to wind that choke. What size torroid or metal thingy to wrap it on? Beats me, big enough to hold that much wire. Double or triple layer it. Won't be as large as a transfer case, but it won't be the size of a 'AAA' battery either. There ought'a be somewhere under there to hide it, sort of.
- 'Doc
Click to expand...
Yeah; exactly what Doc said.
I would splice the torroid into the lines - and the put the caps across the + and -. Then goop it all with silicone caulk - so that it will be water-proof and not allow any shorting if/when the Jeep is partially submerged. That is key.
 
What exactly is a 'DC' transformer? A transformer will only work with AC or a pulsing DC, never a constant DC.
- 'Doc
 

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