Fuel Filter under the cab

[Rally Nova]

I have 1969 GMC 1500 that has a fuel filter mounted under the cab along the frame rails on the passenger side that is leaking. Where would I find a replacement or should I find some female double flare fittings to bypass it?

[Joe67]

Interesting. Is it aftermarket?

I thought all trucks still had it on the carb then?

[wolfthing2000]

Dumpit, ditchit ,scrap it throw it a long way, smash it and forget it after you bypassit!!!! I can't think of a worse place for a filter to service. Just put an inline before the carb and feel good!!!

[Rally Nova]

It looks like a factory unit! It says "AC gas filter replace with GF-15" on it. It looks like a small oil filter.

[wolfthing2000]

Maybe I am wrong! That sounds like a cool thing. I have one similar on an old 52 GMC COE that someone converted to electric fuel pump. Ya might relocate on a fender well and make it more user friendly and more noticeable to boot. Retract my former post in this case. That is as long as you relocate the thing!!!!!

[STP67-72]

I have the same thing on a 69 c-10 and it has it on the glove box sticker.

[Longhorn Man]

get rid of it. A restriction before the pump does nothing but lowers the fuel pressure in that line. Lower pressure means lower boiling point, and this can help contribute to vapor lock.
Place the filter after the pump. It'll work fine, and not help cause vapor lock.

[Stocker]

I tend to trust Andy's advice, but I also gotta mention my own experience with an under-truck fuel filter. My truck has one placed where the fuel line was cut to plumb the 3-way switch for the twin saddle tanks. It was like that when I bought the truck, and I never saw the need to change it. In 28+ years it has never caused me any trouble - I just change it every few years or whenever I think of it. YMMV

[Longhorn Man]

Quite true, it isn't going to cause[ the problems...but it can agravate it. It also puts more of a load on the suction side of the pump which isn't really good for the pump.
Again, not detramental...but does add to the load the pump has to suck on.

[53burb]

I was planning on installing a filter before my fuel pump that I just installed. Is this not recommended?? I was going to put it right before the pump.

[truckdude239]

i was always told that an filter before the pump was good because it kept trash out of the pump. but okay lol

[53burb]

That was my thinking too. Supposedly the fuel pump was replaced shortly before I got the truck about a year or so ago. It went bad and I replaced it a few weeks ago, I was thinking the filter would protect it.

[muddpile]

That's kinda cool as I thought they all had em in the carb. It seems every vehicle is different:
1984 vette: screen filter before electric pump in gas tank, and one canister before throttle bodies.
1972 C10: One small one in carb.
1977 Charger: Canister between fuel pump and carb.

I guess as long as you have one somewhere it works.

[Longhorn Man]

An electric pump has tolorences that are real close....not so in a mechanical.
You can place it before the pump...hech, install 3 of them under there. However, if you are already having vapor lock issues in the summer, then it'll make it worse...and if you aren't having the problem, it may push it all over the edge and induce it.

[SSC's76]

Originally Posted by Longhorn Man

Quite true, it isn't going to cause[ the problems...but it can agravate it. It also puts more of a load on the suction side of the pump which isn't really good for the pump.
Again, not detramental...but does add to the load the pump has to suck on.

Depends, is the tank in cab or saddle. If it's in cab the fuel pump wont know the difference since gravity does most the work anyway.

[Longhorn Man]

Originally Posted by SSC's76

Depends, is the tank in cab or saddle. If it's in cab the fuel pump wont know the difference since gravity does most the work anyway.

Not true. Gravity feed will only feed it 1/2 the fuel it needs (or so) and plus, it'll only get it to the lower portion of the head at best since the carb is higher than the top of the fuel tank... let alone the fuel level.
When the pump is pumping, a negitive pressure condition is constantly in the fuel line. Lower than atmospheric pressure lowers the boiling point. So by reducing the pressure, the chance of vapor lock increases.
This is why late models have an electric pump in the tank. (among other reasons) If you pressurize the fuel, then you raise the boiling point...therefore all but eliminating the chance of vapor lock.

[truckdude239]

oh well i was just saying don't matter to me because mines in lione after the pump and before the carb lol