The Stovebolt Site Forums The Shop Area Engine Shop inline fuel filter question

inline fuel filter pic

There is a small inline filter at the bottom of my fuel tank next to the battery. It is loaded with gunk as you can see in the picture. I can't find a reference to this filter in the shop manual or owners' manual. Is this an original part? My instict is that the inside of my fuel tank is rusty, but I don't know how to check. Should I just replace the filter (any idea what it is)? How do I check my fuel tank and see if there is a rust problem?

This is on a 1946 3800 that was recently pulled out of the barn, overhauled and I'm still breaking it in after the overhaul.

Thanks. Cheers~

picture link doesn't work, it looks like it may be your upload page, asks me to sign in

wasn't any filter between the tank and the fuel pump, a PO must have added it - should be a shutoff at the tank exit .... no doubt the tank is rusty after 60 years, and lots of'em spent sitting with a partial tank of fuel - removing the fuel line and draining the tank may reveal lots [or little] junque - also take out the gauge sender to get a look inside when the tank is empty

Bill

It is a common practice on these old vehicles to put an inline filter between the tank & pump. I do as soon as I get one. They are available at any parts store. They go by the size of the hose/tube. 5/16 usually but 3/8 sometimes. I would replace the filter & keep an eye on it. If it gets a lot of grit or water it's time to take off the tank & clean it or get a new one. Getting stranded on the road with a clogged up fuel system is no fun.

Ok, I have fixed the link. I will replace the filter and keep an eye on that one.

Thanks guys.

carefully remove the fuel gauge sender from the top of the tank.With a flashlight you should be able to see into the tank.I'd bet the PO put the filter in to protect the pump from junk in the tank

While I agree with everything posted above, and I have seen many installations of the standard-style bowl-type fuel-filters and after-market in-line fuel-filters that work fine between the fuel tank and the fuel pump, I had problems with a standard-style bowl-type fuel-filter and then an after-market in-line fuel-filter between the fuel tank and the fuel pump. It was suggested to me to move the filter to the output side of the pump. This suggestion came from a dual-carburetor supplier - the reason was that supposedly there is a marginally stronger pressure side of the fuel pump, in comparison to the vacuum side of the fuel pump (an accomplished in-line-6 engine-rebuilder concurred with this suggestion).

I am not interested in an argument about this, I am only posting what I was told, and what worked for me (problem solved - after trying three different, new, fuel pumps). This may not be necessary in most applications, but, if you seem to be fuel-starved after putting a fuel-filter between tank and pump, maybe this will solve your problem.

I'm with Tim, filters betwixt the tank and pump are trouble - the pump will pass any junk that fits thru the line with no problems, best to have the filter up in the engine compartment where you can glance at it every time you check the oil, don't have to remember to crawl in the dirt regular draggin a light along

Bill

Since I'm going to replace the filter anyway and if there are not any problems with having the filter between the pump and carb, I might as well move it. Is there one spot that is better than another to put the filter? Conversely, anywhere it should not go that might not be immediately obvious?

Just to throw in something to back up what Tim said, on late model EFI vehicles, the pump is located before the filter, nowadays always in the tank, for just the reasons exlained. Most feul pumps are better pushers that pullers.

gripped - the position for the original style filter with the glass bowl is right at the carb inlet - easy to replace, easy to see

Bill

Not trying to hijack your thread. I just installed a inline filter between the tank and pump, and first time I stuck my foot in it the float stuck and flooded out the carb. So I'm thinking the filter starved the carb and caused the float to drop and stick? I'm running 350 with Q-jet.

Chances are you knocked something loose when changing the filter or your Q-jet and lodged it in the needle and seat. Q-jets like very clean fuel.

As far as fuel filters before or after the pump, after is always better, but if you install a bigger filter before the pump and keep it clean, it won't effect them at all. Another thing you have to remember is that from tank to pump is a fairly short distance on a truck, so the pump isn't really working that hard pulling fuel. Now if the tank is way out back, or you have a thirsty big block drinking loads of fuel, then yes, you need to move the filter.

If its already in place and working, replace it often or till it clears up, install a filter before the carb inlet and enjoy the drive.

Joe

Joe's comment about distance to the fuel tank might be a factor in my problem. The Suburban fuel tank has a fuel line that is about three times longer than that for a regular cab.

No worries about hijacking the thread, I'm happy learning all about my vehicle and I am looking to hear about others experiences. After all, that is why I am here

Forgive my ignorance and thank you for your help, but there is an unknown (to me) cylinder just before the carb. The fuel filter is an "XL Fuel Filter" and everything is working fine, so I think I will just replace the filter for now to avoid creating a cascade of problems by trying to move it. Any clue what is inline next to my carburetor?

That's just another inline fuel filter made of metal, instead of see thru plastic.

So my instinct was correct. Seems like a lot of filters, but it runs well!

Dirt can foul up a fuel pump. It gets in the check valves & causes it too loose pressure. I have been putting them between the tank & pump for many years & will keep on.

Untill you are sure of the condition of the fuel tank, keep all the filters you have for good insurance. I would replace them both for now and then just the lower one later on, it should catch 99% of the crap and the top one is just there for good measure.

Joe

I just bought a 1945 Dually from Tenn. It had a filter about 6" from the carb. It had a lot of rust in it. I replaced it with one from Auto Zone. Had to put gas in carb to prime to get started. Drove around for a while in a parking lot to see if O.K. I am going to watch to see how much rust continues. Then figure out what to do next. Now I need to go through the brakes completely.

Anybody know about them, send me the threads or search keywords.

Mark Miller
Lex, Ky

I believe this is another issue with no definative answer; the answer really depends on each situation.

While I won't disagree with any that state the filter should be on the pressure side of the pump, please consider the following:

Years ago, we sold fuel pumps. Carter brought out a wonderful (my opinion) low pressure pump called a "gerotor". This was a small rotary type pump. And we sold tons of them. Carter suggested a filter BETWEEN the tank and the pump. We started to get returns, and found no filter had been installed. Cut the pumps open, and would find a small rust particle which would lodge in the pump. Within a year, Carter sold the pumps with a short piece of fuel hose and an inline filter already installed on the pump. End of returns.

Unfortunately, when Federal Mogul bought out Carter, this pump was discontinued, probably because some "efficiency expert" saw the early number of returns, but not the solution.

Jon.

Thanks all for your help. I purchased two new filters to replace the aforementioned ones. I will replace them where they stand. The shutoff valve at the tank (petcock?) is broken, but I think I can still turn it with some pliers. So that takes care of turning the fuel off so I can replace the filters. After the filters are replaced I will turn the fuel on, is there anything I need to do to get the truck started. Mark mentioned gas in the carb, will this be necessary? If so, how do I do that? (I've only owned EFI vehicles) Cheers~

Done. The fuel tank didn't completely close off, but I worked quick and only got a minimal petrol shower while under the truck (it was probably a good thing that I was wearing goggles though!). Not much mess with the filter nearest the carburetor. The truck fired right up after changing the filters without issue and I let it run for several minutes, again without issue. I will keep an eye on the clear filter nearest the tank.

Thanks all for your help.

Glad to hear it worked out.

Joe

From my experience, dirt/rust will compromise a fuel pump.