# Fuel Filter Question
**URL:** https://boards.straightdope.com/t/fuel-filter-question/337397
**Category:** Factual Questions
**Created:** [December 28, 2005, 3:25am UTC](https://boards.straightdope.com/t/fuel-filter-question/337397 "2005-12-28T03:25:50Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@Runs\_With\_Scissors](https://boards.straightdope.com/u/Runs_With_Scissors)
#### Post date: [December 28, 2005, 3:25am UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/1 "2005-12-28T03:25:50Z")
Inspired by this thread:
> **[How can I clean my truck's fuel system](https://boards.straightdope.com/sdmb/showthread.php?t=351399)**
>
> I’m pretty sure my truck’s fuel system is dirty and/or clogged, it is reaching the point where if I don’t press on the gas when I first start it up the engine will die (but after I get it started it will idle). What all can I do to clean it? I...
I have a 99 Dodge Ram 4 x 4.
Oil Can Henry recommends changing the fuel filter. Sounds right. But…they said it’s in the gas tank, so they can’t do it. Take it to my mechanic.
My mechanic said, “Yeah. It’s in the gas tank. We won’t touch it.”
_sigh_
It’s never been replaced…if you know about such things (unlike me) what would you do in this situation?
---
### Author:  [@Gary\_T](https://boards.straightdope.com/u/Gary_T)
#### Post date: [December 28, 2005, 3:39am UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/2 "2005-12-28T03:39:56Z")
First, have testing done to see if there’s any evidence that the filter is restricted. If you have a specific symptom, there might be something else causing it.
If and when you decide the filter should be replaced, take it to a shop that’s not afraid of doing it. It’s not that big a job. It strikes me as odd that an auto repair professional would decline to do it.
---
### Author:  [@AzureM](https://boards.straightdope.com/u/AzureM)
#### Post date: [December 28, 2005, 3:47am UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/3 "2005-12-28T03:47:08Z")
I’ve got a Jeep, and _I believe_ it has a similar sending unit to your truck. The filter/pump/fuel level sensor is all in one cylindrical unit that is bolted into the fuel tank through a hole in the top. AFAIK the entire sending unit must be replaced if one wants a new filter. Not only is the unit somewhat expensive, it is a PITA to get at. I dropped the tank from my Jeep and it was not the easiest thing I had ever done. I’m sure the process would be quite similar to your truck, and I would think the labor costs to have a mechanic do it would lighten your wallet significantly.
Unless you are experiencing problems with performance or mileage, I’d probably just leave it alone.
---
### Author:  [@Runs\_With\_Scissors](https://boards.straightdope.com/u/Runs_With_Scissors)
#### Post date: [December 28, 2005, 4:05am UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/4 "2005-12-28T04:05:45Z")
> [@AzureM](#):
>
> Unless you are experiencing problems with performance or mileage, I’d probably just leave it alone.
I’m not having problems…I’v just wondering if one that is a '99 (about 75k miles) and has never been replaced should be replaced.
Thanks for the info!
---
### Author:  [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)
#### Post date: [December 28, 2005, 6:43am UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/5 "2005-12-28T06:43:58Z")
The filter on the sending unit is called a sock filter, IIRC.
Its meant to keep out the big chunks out of the fuel line.
My old Integra had a fuel filter bolted to the firewall; cheap and easy to replace.
You sure you don’t have one of those somewhere between the engine and tank? I’ve seen applications where a filter was bolted to a frame rail.
---
### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [December 28, 2005, 4:08pm UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/6 "2005-12-28T16:08:20Z")
**Enola** Some car makers are also putting the main filter in the tank now, not just a sock.
I would suggest you consult your owner’s manual and find out how long the guys that designed the system think it will last. I know of a couple of cases where there is either no replacement listed, or the replacement is at a very high mileage like 150,000 miles.
---
### Author:  [@Gary\_T](https://boards.straightdope.com/u/Gary_T)
#### Post date: [December 28, 2005, 7:04pm UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/7 "2005-12-28T19:04:33Z")
> [@Enola Straight](#):
>
> The filter on the sending unit is called a sock filter, IIRC.
> Its meant to keep out the big chunks out of the fuel line.
>
> My old Integra had a fuel filter bolted to the firewall; cheap and easy to replace.
> You sure you don’t have one of those somewhere between the engine and tank? I’ve seen applications where a filter was bolted to a frame rail.
Sock filters are used on the fuel pick-up tube inside the tank, whether it’s just a simple tube (with external fuel pump) or part of an in-the-tank pump. Its job is to keep debris out of the fuel pump. The vehicle in question surely has one of these, but also has a filter on the output side of the pump, mounted on the pump/sender module. Why some car manufacturers choose that location over a more easily accessible external location such as you describe is beyond me, but that’s what some of them do.
---
### Author:  [@Gary\_T](https://boards.straightdope.com/u/Gary_T)
#### Post date: [December 28, 2005, 7:21pm UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/8 "2005-12-28T19:21:06Z")
> [@brian\_ax](#):
>
> I’m not having problems…I’v just wondering if one that is a '99 (about 75k miles) and has never been replaced should be replaced.
Chances are it’s fine for a while. I don’t find it listed on the maintenance schedule. I’m sure it’s designed to last longer than a typical easy-to-access fuel filter, although I don’t really know how long it will last.
The question “should it be replaced” is a tough one. We don’t have a manufacturer’s mileage recommendation. We know it won’t last forever – all fuel filters eventually get restricted doing their job. As it gets significantly restricted, it puts additional strain on the fuel pump. If it gets clogged, the vehicle won’t run. So, as with any fuel filter, it’s desirable to replace it before it gets too restricted. But factor in the relatively high cost of doing so, and it’s questionable whether it’s cheaper in the long run to replace the filter a time or two, or just wait until the pump goes bad and replace the entire pump/sender/filter assembly. Testing is unlikely to indicate a problem until it’s significantly restricted, and the cost of the testing is another thing to factor in. I’m afraid I don’t have a simple, clear answer as to when, or even if, the filter itself should be replaced. That said, if I had to suggest a service interval, I’d be thinking somewhere in the 100-120K miles range.
---
### Author:  [@Rick](https://boards.straightdope.com/u/Rick)
#### Post date: [December 28, 2005, 11:06pm UTC](https://boards.straightdope.com/t/fuel-filter-question/337397/9 "2005-12-28T23:06:33Z")
> [@Gary T](#):
>
> Why some car manufacturers choose that location over a more easily accessible external location such as you describe is beyond me, but that’s what some of them do.
Ohh, Ohh I know this one. 😃
Every time you put a joint in the fuel system there is a potential for hydrocarbon leakage. As evap standards get tighter, fuel systems have to get more vapor tight. On our PZEV cars they changed the tank material to stainless steel, and put the pump and filter inside the tank. So by moving those intems into the inside of the tank, you prevent a bunch of hydrocarbons from being released into the air.