Safety In-line fuel filter

[E Rutherford]

I had not driven my Coupe for a couple of months, so since my wife and I were enjoying a solo Christmas this year, a maintenance drive was on the list for the day. Also its one of the few times during the year when you see less than 100 cars on the road in 4 blocks!

I like using a clear inline filter between the fuel pump and carbs. Porsche service bulletin recommends a piece of fuel line there to eliminate vibration which may cause the loosening of the banjos at the carbs. Plus I always install primer pumps in all the cars I have, so the clear sight glass allows me to see that fuel is reaching the carbs.

The problem, this particular filter has two ends that tighten down on the glass with gaskets. With the car sitting for a period of time, these gaskets dry out and the connection is no longer tight and LEAKS fuel a lot!

I always open the deck lid and turn on the primer pump and check for leaks before firing up the car out of habit. The check paid off this time, it was leaking like a faucet! A quick fix and the maintenance drive was completed.

In the safety classes I have presented, this "habit" is passed on to the participants. Check for leaks of any kind when first starting up your car, especially if its been sitting.

As for this filter model, either make it a "habit" to tighten the ends or find a suitable replacement.

ed
klasse356.com

[Erik Thomas]

If I am compelled by fuel tank filth to add a filter, I use an all metal filter from NAPA. I can feel when the carbs are full by the plunger on the pump, it bottoms out when the bowls are full, thus, there is no need to "see" the fuel. I have also been replacing the German fuel hose with hose that is not eaten by the alcohol in the modern fuel. The 356 has a tank strainer, a bowl and a screen below the tank, a screen at the pump. Unless the fuel tank is a mess, there should be no need for an inline filter. Also, if you put the filter ahead of the fuel pump, instead of behind it, it keeps the crud out of the fuel pump.

[Dan Epperly]

If I am compelled by fuel tank filth to add a filter, I use an all metal filter from NAPA. I can feel when the carbs are full by the plunger on the pump, it bottoms out when the bowls are full, thus, there is no need to "see" the fuel. I have also been replacing the German fuel hose with hose that is not eaten by the alcohol in the modern fuel. The 356 has a tank strainer, a bowl and a screen below the tank, a screen at the pump. Unless the fuel tank is a mess, there should be no need for an inline filter. Also, if you put the filter ahead of the fuel pump, instead of behind it, it keeps the crud out of the fuel pump.

That's were I put mine, plus the pressure is minimal and less likely to lead to leaks then if you mount it after the pump.
I always use those cheap plastic ones, never had an issue with them.

[David Jones]

The fuel filter question gets revisited it seems every few months. maybe there should be a sticky for it? I still believe there is no need for yet another filter when Porsche already have 3 originally installed. If you have aftermarket carbs such as Webers they also have filters on the carb inlets so you could have 5 inline filters in all. All the last one is likely to catch is debris from a failing fuel line so you are already too late in fuel system maintenance. Has any one got a story of how their fuel filter saved them when crud got through from somewhere after the last Porsche filter in the fuel pump or from the fuel cock filter if fitted before the pump? I have always removed all filters from all of my 356 cars and never ran one on the race car on principle and never suffered from carb clogs in 30 years of racing. I did suffer from a split fuel filter that sucked in air instead of fuel once on a borrowed race car. That took a while to find.
There are I am sure a few stories of fuel filter issues but I doubt there are many. Reminds me of a friend who told me to avoid the boxster a few years after it came out as he saw a lot of them needing various repairs out of warranty in his shop in California. I pointed out to him that as he was a repair shop that is what he should expect but that he never saw the cars that did not need repair and there were far more of them.

[Wes Bender]

One wouldn't think an additional filter would be needed, but like Ed's, I have the same kind mounted there too. The Pyrex glass lets me see what's going on with fuel flow. I suspect that there are as many opinions regarding fuel filters as there are members of the forum.

[E Rutherford]

Remember the purpose of the thread be aware of an issue with an in line fuel filter, NOT whether additional filtering is needed.
BUT if you do decide to put one of these in or have one already, be aware of an issue.

ed
klasse356

[Vic Skirmants]

One word of caution regarding the plastic filters; some have dual-step ends so that either the smaller VW-size fuel line or the larger Porsche line can be used. PROBLEM is: the small diameter part restricts the fuel flow!

[Martin Bruechle]

When I was a mechanic 70's 80's we would sometimes get VWs in for engine fire repairs.
1/2 the time it was those glass filters would leak and cause the fire from the distributor spark.