tyncobb

Just went to the Junkyard and removed a 94 LS400 Fuel Filter and Charcoal Canister from a very low mileage (57,000) T-Boned LS400. I am going to replace my own 94 LS400 fuel filter and canister this weekend, with these parts. Can anyone tell me; if I disconnect the Fuel Pump Relay (behind the gas/fuel inlet and the interior box on the rear passenger side) if that will disconnect the electrical connection to the Fuel Pump ? Or will I need to pull the back seat out, pull the fuel pump out and disconnect at that electrical connection. Plan on taking the gas cap off and disconnecting fuel pump electrical connection and then pulling fuel filter and canister at same time so I don't have a huge spurting gas line and possible mess with 1+ gallons of fuel when I disconnect the filter. Then I would plan on connecting all fuel hoses, electrical connection and turning ignition on and off about 3 times to refuel the line, before I try to turn I over. ANY Help or Hints would be appreciated before I do this job this weekend. Thank you, Tyndale Cobb

RugbyDad

I believe, and I may be totally wrong as I've never done this, the correct procedure is to turn the car on, remove the fuel pump relay, run the car until it cuts off, remove gas cap and proceed with r&r of filter.

91LS400vgb

Most likely you'd want to remove the fuel pump relay first, then turn the car on, run it until it cuts off, then remove the gas cap.
Also, do you mean the regular fuel filter as in this?

I would never advise installing a used fuel filter - I would just buy a new one. They're not too expensive.

Michael

I have a brand new fuel filter sitting at home which I am not attempting to replace. I am afraid that the bolt would strip and the line will bent as there are so much rust around and on the fuel filter, itself. If anything goes wrong in the process, then what? The problem will be much more complex. I would like to replace the fuel filter but.... I am hoping the filter will last the life time of owning my 93 LS.

I do not know if you are in rust belt area but let me know how it goes. If you are going to replace the filter, I would go with a new one.

tyncobb

91LS thank you for the instructions, that hint to remove the fuel pump relay and then run the car until it cuts off will save me much frustration and gas squirting all over the place. Yes that is the fuel filter that is on my car and the same one that I pulled from the other 94. I will also take your advice to put in a new one since they are only $25. Thanks again for the help, you'll have made my job much easier for both the filter and charcoal canister this weekend.

91LS400vgb

It can be difficult to remove the old filter. Use plenty of PB Blaster or CRC Freeze-off and make sure you use two wrenches (one to hold against) and try to not to damage the lines.
I've done this job twice (2 different LS's) and I can tell you that it is not fun. The fuel will just keep flowing out so you have to be fast, but at the same time you need to be careful, because you don't want to cross thread anything. You can save some time by making sure your new filter already has the bracket installed on it (hopefully you got the bracket from the salvage yard, or your new filter comes with it). I had gasoline running down my arms while I was changing it, so it wasn't a pleasant experience.

oldskewel

iTrader: (1)

I recently replaced the filter on my '91. Before doing that, I searched this site and read up on everything I could find, including the fuel pump relay thing. In the end, here's what I did, which in hindsight is exactly what I would do again:
- back car up onto car ramps - since the rear jack stand would be right in the way if I jacked it instead.
- test-loosen and re-tighten the fittings on either end of the fuel filter - just to see if they're stuck. Based on what I had read, I was prepared for a hassle, but mine were perfectly easy. Maybe another hidden benefit of the high cost of living in California.
- I did not bother to deal with the fuel pump relay, since that will just depressurize the fuel lines, saving a tiny amount of fuel leakage, as compared to what will leak out anyway due to gravity, whether or not the line is initially pressurized. I did read an easy sounding tip that I did use: remove the gas cap to let any excess vapor pressure out (since that would continue to pump the fuel out rapidly), and then re-install it, so once some fuel leaks out, the partial vacuum will slow the flow. Easy to do that one, and it makes sense, so I did it.
- Used an oil-change pan to catch any leaking gas.
- I spent a little time custom building plugs (using the new filter to test for a good fit) - I used a number of soft clear plastic hoses, inside eachother with a golf tee in the center of them all - worked perfectly.
- So then the task was to remove the fuel line from one end of the filter, plug the old filter, screw the new filter into the fuel line ASAP, with the other side of the filter already plugged. Then on the other side. Basically, working as fast as possible to plug the open lines to minimize the inevitable fuel leakage.
- It all went very well. I'll guess about 6-8 oz of gasoline leaked out, plus what was inside the filter - which was really weird looking stuff by the way - oily/watery stuff that did not mix with the fuel. I guess the filter did its job well.

I'd say that disconnecting the fuel pump or relay won't hurt, but won't really help either. Not relieving the fuel tank vapor pressure could really cause problems, so make sure you do that. No matter what you do, when the fuel lines are disconnected from the filter, fuel will flow out due to gravity, even if you have eliminated any line pressure or tank vapor pressure, so be prepared to catch whatever comes out and be prepared to make the change quickly.

Also, I really would not do all this to put in an unknown used filter. Get a new one.

johnnyg66

Be quick and safe and a new filter is really not a whole lot more. Also loosen the nut that holds filter on first it will make taking the filter out easier.

Yamae

Don't mislead people guys.
The fuel pump relay for any LS400 cannot to stop the DC supply to the fuel pump. It only bypasses the fuel pump resistor. You have to be careful what you write.
Remove the circuit opening relay to stop the fuel pump.

Michael

Does anyone know the recommended, published mileage for filter replacement on LS?

oldskewel

iTrader: (1)

For my '91, it is 60k miles.

But I think this is one of those things where it all depends on how clean the gas is that you put in the car. Always clean gas = never need to replace. Often dirty gas = may need to replace sooner than 60k.

When I did mine, I already had it in my parts inventory, and I had a problem that could have been fuel related, and it had been 66k miles since the filter was replaced, so I just did it. The problem (codes 25 and 26) was fixed, but I also replaced O2 sensors (were original at 188k miles) and replaced the ECU capacitors, so I'm not sure which of these was the real problem (my guess is ECU, but others were "due anyway"). Based on the gunk that poured out of the filter after replacing it, I think it was due.

Michael

One cannot control the fuel cleanness. You take what is provided by the fuel suppliers....

I still have original filter with the mile indicated below. I do not know if I should be alarmed......