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Disconnecting fuel filter from rusty steel fuel lines

My 1995 S-10 pickup had the fuel pump die after 130,000 miles. After replacing the pump, I figured that I possibly stirred up a lot of stuff off the bottom of the gas tank when I removed it from under the car and that it would not hurt to change the filter. I managed to loosen one line from the filter using open end and line wrenches. The other connection is rusted together. I have been soaking this fitting with penetrating oil, tapping on the steel line, the nut and the filter with a piece of steel thinking that the vibration might help the oil seap in between the pieces. I have even tried putting a bit of heat to the fitting using a soldering gun, then spraying with cold water. (I have had good luck like this when using a torch, but not around fuel lines and gasoline). Other then keep soaking with penetrating oil,do you have any ideas on how to seperate these fittings without twisting off the old steel fuel line? Thanks Fred

What are you using for a penetrating oil? Some work better than others.


I think it is called CRC

STOP using a heated element/spark producing tool near the fuel lines. when/if it does break free having gasoline near an electrical tool is a potential for DISASTER.

how far away is the next connection if this breaks, to replace the fuel line too?

does this fuel line have a hex head fitting? although this is right next to the hex nut on the filter, you should be able to get wrenches on both to lever against to loosen it.

I might even venture that this is the EXACT reason why high quality wrenches, with good quality finishes make these types of jobs easier, since you usually only get one chance to get the connections apart, without slipping, buggering up the hexes, and requiring more repairs. (read quality as in NOT china/korea made tools)

AND adjustables ARE NOT the answer.

usually these fittings are best done with the “flare nut wrenches” so you get an extra corner and have wide 6 flat sides and corners to turn on. (as opposed to 12 point sockets, which have small corners to grip on) and a rusty fuel line is JUST the type of fitting which has lost just enough steel to make a 12 point or open wrench fit loosely and strip the corners off.

Nothing I can add except that sometimes things will rust together bad enough that something can be destroyed during disassembly and there’s nothing to be done about it.
Changing the fuel filter on a regular basis will also allow the fuel pump to have a longer life.

try PB Blaster for a penetrant it’s GREAT

Hold the line stationary and turn the filter. Locking pliers may work if you’ve already rounded off the fittings.

I’d second the PB Blaster. Also maybe use a crows foot wrench with a ratchet to get more leverage provided you can hang onto the other fitting. But it may be beyond repair at that mileage and will require replacement.

Just a word of warning around fuel-last week a salvage worker was drilling a hole in a gas tank with a portable drill. Gas leaked into the drill, started a fire and blew the whole building up. Doesn’t take much of a spark if conditions are right.

This happened on my Silverado. Had to cut the line before and after the filter and install new short section of fuel lines. I think they sell the sections at the parts store complete with fittings compatable with the fuel filter and the nescessary couplings - I think that is where my mechanic bought them. Otherwise, buy a section of new steel fuel line, match the fittings on the ends of the fuel filter, and cut the old lines back far enough where you should be able to install couplings between the old fuel line and the new sections.

I’ve seen those kits on the Help! rack, IIRC. This is probably the best bet.

Actually the best penetrating oils are Liquid Wrench and one made by Seafoam (according to tests I’ve seen online)
Anyway I’m looking at this and see that it’s a common problem with fuel filters & pumps. I think the best way to deal with it is to use antiseize on everything that has to come off in the future (maybe a different type of grease is better)

This post is 11 year old. The OP probably doesn’t have this car anymore.

In a recent test (by Project Farm on Youtube) the top penetrating oil, of the 5 or 6 he tested, was Liquid Wrench. PB Blaster was also tested but fared poorly. In another test, the Seafoam penetrating oil came out on top but neither Liquid Wrench nor PB was included in that one. I think he plans to do a test between Seafoam and Liquid wrench soon.