Replacing Fuel Filter

[michaelcrisp]

I would like to replace the fuel filter on my 1987 944 NA. One the steps in changing the filter says to clamp the fuel line shut to prevent the fuel escaping the fuel tank. The lines on either side of my fuel filter seem to be rather hard and not likely to clamp shut. One is in fact steel while the other looks like black rubber hose but is very solid.

Which hose do I clamp? Are my lines so old that they have turned hard and need replacing? Or, am I looking at the wrong line that needs clamping shut?

Any sugestions would be appreciated.

Regards,

Michael

[zedsn]

Hi, you will want to clamp the hose that comes right out of the bottom of the tank but don't put too much pressure on it and if it isn't flexible I beleive that you will need to replace it. I went to a hose shop that specialized in hoses and bought 2 feet of a specific hose that would take the gasoline and pressure rating and double clamped it from the tank to the pump but I don't think that there is much pressure before the pump only after the pump but wanted to be safe. Hope this helps.

[minton2001]

Amazing thing, this forum. Slightly different question though: What would be the symptom(s) of a partially blocked/ old fuel filter?

[hopps]

I'm not sure about a partially blocked fuel filter, but an old one could leak as mine did. I did notice that the car ran 20x smoother than before with a new fuel filter! It starts up a little faster, but more than anything it's a smooth ride!

[alantica]

The line from the gas tank is the rubber line. To stop the fuel flow use a pair of vise-grip pliers that don't have any teeth. If your pliers have teeth, you can cut a piece of rubber hose and slide over the teeth, or wrap a cloth around each side. Just like cutting off the outflow of a water hose, you are just pinching the line.
The metal line is the outflow line to the fuel rail. Those nuts can be a real PITA (pain in the a$$ - read your other note ) So you may want to spray some WD-40 or other lubricant to help loosen the nuts. Just be careful with the nuts on the metal line. If you strip the nut you will have to pull the line off and have a replacement nut put on in a machine shop or order another fuel rail. It is best to use the metric wrenches and not an adjustable wrench. Good Luck!

[earlr85944]

a partially blocked filter can give hesitation upon accelleration.
if changing the filter it would be the time to check the tank strainer, it unscrews and is the part that the hose coming out of the bottom of the tank is connected to.
you have to have an empty tank to remove it, so its then a good time to flush the tank and start w/ everything fresh and new!

[alantica]

Michael - The fuel filter/cartridge is a one way flow filter, so make sure you have the outflow arrows pointed to the metal fuel pipe going toward the front of the car.

minton2001 - a partially blocked filter. If a filter has crud in it (rust, tar), it will normally slowly give symptoms of choking, poor running, sudden surges, cutting off and eventually not starting at all. If the filter is retaining water, it will be hard to start and run poorly or sputter until more fuel is pumped through the filter. If the 944 is parked for a long time, this could be the problem. A DD will just have poor starting, continuous cranking, after being parked for say, more than 10 or so hours. You would not notice a problem for short trips that are repeated.
A gas dryer (STP, etc..) may help, but the long term fix is to run the tank near empty. Disconnect the rubber hose at the filter, put the ignition in the start position (not cranking - just letting the pump drain the tank) then replace the filter. A typical problem in cold weather because any fuel in the tank, line or filter will float above water.

[SolReaver]

Instead of clamping the lines I use golf tees, spark plugs, or older stepped caps off of Sealant tubes. Whatever is handy to plug the hose. The Mounting bolt can be a real pain so figure it may take a while. While you are there, consider draining the tank and removing the strainer, replacing the Strainer O ring. Lotsa crud can be in there. FFilters should be replaced frequently. Cheap insurance for your injectors and pump.

[minton2001]

Used the no clamp/ fuse out method. Not that much gas at at all. Couldn't get to the rubber hose to clamp it off anyway (this is something no one mentions). Seems to have greatly improved the extremely rough running that lasts for about 30-60 seconds after a cold start on my car. We'll see after a dead cold start tomorrow. Now I've got to track down that whine....

[jep32]

Which is the fuel pump fuse? Just pull it out while the car is running?

[mytrplseven]

Just pull the DME relay. It controls the fuel pump.

[Peter Burrowes]

The latest issue of Excellence has a very good article describing this with pics

[guywitha968]

Which issue specifically? Does the article cover fuel pump, fuel filter or both? Thanks.

[968 GUY]

You should look at the check valve also. It helps keep the fuel rail pressurized.