Double inlet fuel filter

[Crusty Jeep]

What's with the double inlet fuel filters? The smaller inlet seems to be sucking air from a fuel tank vent hose? This old pig starved for fuel the other night while idling on an incline and I had to disconnect and plug that second inlet to get it started. Is there supposed to be some sort of valve or something to keep it from starving? Can I just rip out the second line and put a normal fuel filter in (simple is better)?

[carnuck]

It's actually a double outlet filter for the carbed rigs. The small line MUST be in the 12:00 position because it's the vapor return line. Probably more likely you had gas line ice up this time of year though.
The other possibility (especially if you fuel up at Arco or the other cheapo stations) is the gas sock in the fuel tank is turning to mush from the first batch of winter gas or someone going too gung ho on the alcohol.
It seems to be a Jeep thing, but other cars are affected too. (you'd be surprised how many XJ and ZJ fuel pumps get changed when the only thing wrong is the gas sock collapsed and blocked the line off!)
If you have crud in your fuel line (even ice crystals), it will come up and jam the inlet valve of your fuel pump open, so no fuel pressure can be made.
I recently had to drop the tank out of my J4000 again because some SOB's tried to steal my gas with a rotting rubber hose and left lots of chunkies in the tank (a piece of it broke off and was floating inside. It wasn't there when I put this tank in my truck back in June) I replaced the fill nozzle with the newer design (off the '83 Cherokee my son is turning into a buggy), which makes filling the tank MUCH nicer too!

[Dude]

Originally posted by carnuck
Probably more likely you had gas line ice up this time of year though.

I might be wrong , it would have to get alot colder then it has been for you to have a icing problem in the fuel system. I lived in the cold country(grew up there) and it wasn't even an issue untill you got close to the 0* or below.

[carnuck]

With the crap gas we have around here, the freezing level drops to 31 degrees.

[Crusty Jeep]

The whole starting problem can be explained by the fuel filter and return line combo causing what amounts to a big old vacuum leak in the fuel line. The pump is sucking air in with the fuel, and when the incline gets too much, gravity overcomes what little suck power is left. You can test it by sucking on the outlet side of the filter. You get no positive vacuum, just lots of air, but if you suck hard enough you'll finally get some fuel too.

My Haynes manual is of little help, as usual :rolleyes:

And no, there's no way it's ice. This happened before the temp took its nose dive, I was in a t-shirt for part of the day, so no ice, not in the lake, not in the clouds, and not in my fuel line.

[Dude]

Originally posted by carnuck
With the crap gas we have around here, the freezing level drops to 31 degrees.

:rolleyes: :rolleyes: :rolleyes:

[carnuck]

That would make sense IF the filter was before the fuel pump! The filter is between the pump (after the pressure) and carb. As the pressure builds up, some fuel is forced back to the tank along with any vapor bubbles in the line. Knowing now that the temp was higher than I thought tells me your gas tank's "sock" is either clogging up from crap in the tank or collapsing from the fuel additives (mostly MTBE. There was quite the write up about it in the ASE forums a couple years ago)


Originally posted by CrustyJeep
The whole starting problem can be explained by the fuel filter and return line combo causing what amounts to a big old vacuum leak in the fuel line. The pump is sucking air in with the fuel, and when the incline gets too much, gravity overcomes what little suck power is left. You can test it by sucking on the outlet side of the filter. You get no positive vacuum, just lots of air, but if you suck hard enough you'll finally get some fuel too.

My Haynes manual is of little help, as usual :rolleyes:

And no, there's no way it's ice. This happened before the temp took its nose dive, I was in a t-shirt for part of the day, so no ice, not in the lake, not in the clouds, and not in my fuel line.

[Crusty Jeep]

Originally posted by carnuck
That would make sense IF the filter was before the fuel pump!
It IS before the pump! The pump draws from the single fitting end of the filter.

Did the SBC-350-Retro-Fitter-Guy (TM) screw the whole thing up?

[carnuck]

Originally posted by CrustyJeep
It IS before the pump! The pump draws from the single fitting end of the filter.

Did the SBC-350-Retro-Fitter-Guy (TM) screw the whole thing up?

That would do it! LOL! Get a 2 line filter and that'll fix your problem (except you'll need to do something with the vapor line)

[Crusty Jeep]

I love it when people throw stuff together completely bass ackwards and then go duh... I think it works fine... duh :rolleyes:

Thx carnuck, i think I can get this sucker routed right now :cool:

[carnuck]

If you move that style filter above the fuel pump it'll work fine.

[Crusty Jeep]

OK I re-routed the fuel lines. It now goes:

TANK -> PUMP -> FILTER -> CARB and RETURN (double output here).
The vent/return line is even at 12:00 (was it supposed to AM or PM :finger: ).

Ya know, some guys would have gotten a clue by the little stamped 'IN' on the single fitting end, but not me :rolleyes:

So in the great redneck tradition, I now say, It Works Fine (TM) :redneck: