Thoughts on fuel filters

[Tinster]

Aweman sent me a website that produces very fine sized
fuel filters. This got me interested and I am doing some research. Here's a bit of technical write up that is interesting since it seems to apply to Triumphs.

<span style="color: #990000">A note on fuel filter selection:

If you have a high-performance fuel system, Marren Fuel Injection recommends that you incorporate fuel filters before and after the fuel pump. A low-restriction (coarse, 100-150 micron) fuel filter should be installed between the fuel tank and the fuel pump inlet to protect the pump from sediment. A fine filter (10 micron) should be installed between the fuel pump and the injectors to ensure that small particles of debris that make it past the fuel pump do not clog the injectors themselves.

Why not just run a fine-element, 10 micron filter before the pump? Fine-element filters will trap a lot more debris than the coarse filters, but they are considerably more restrictive. Because of their high filtration rate, they also become restricted much more quickly. Any restriction on the inlet side of the pump can cause that pump to eventually self-destruct! There are two main reasons for this. Cavitation occurs when the supply of fuel to the pump is restricted, causing small pockets of air or vapor to form in the fuel. These pockets can literally hammer a pump to death. A restriction on the inlet side will also cause vapor lock. The restriction will allow the fuel pump to pull a vacuum on the inlet side, which will drastically lower the boiling point of the fuel. In plain English, the liquid fuel boils inside the fuel line and becomes a vapor. Since the fuel pump can only pump liquid (not vapor), the fuel supply to the engine is cut off. Remember that fuel pumps are cooled and lubricated by liquid fuel (not fuel vapor), and vapor lock can cause fuel pump and engine damage. For this reason, keep a coarse-element filter between the fuel tank and fuel pump, and a fine-element filter between the pump and injectors.

NOTE: Most OEM-style in-tank fuel pumps are equipped with a low-restriction inlet filter, often known as a strainer or “sock” (see photo right). These filters often clip or screw onto the inlet side of the fuel pump. This is considered a coarse-element filter, and if you use an in-tank pump, this is a good low-cost alternative to an external coarse-element filter. However, we recommend that you still use a fine-element filter after the fuel pump to protect the fuel injectors.
</span>

 

[Guest]

The first sentence in paragraph 2 would appear to exclude Triumphs. Especially carb'd models...

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]If you have a high-performance fuel system[/QUOTE]

:laugh:

btw: I have this sort of setup.
It's not cheap, so I guess it's not a Triumph any more...

 

[Tinster]

The first sentence in paragraph 2 would appear to exclude Triumphs. Especially carb'd models...

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]If you have a high-performance fuel system

:laugh:

btw: I have this sort of setup.
It's not cheap, so I guess it's not a Triumph any more...

[/QUOTE]


<span style="color: #990000">I cannot name a single component in your photo. Care to identify
parts for us know-nothing mechanical TR owners?

d </span>

 

[Guest]

The big metal thing is a stainless steel fuel tank.
The little metal thing is the battery box.

The black thing under the fuel tank is a fuel cutoff switch - you really want one of these! My tank is baffled and has twin takeoffs - they meet up at the cutoff. Be aware that cutoffs for AN fittings are as rare as hen's teeth though.

There are three red things connected together under that.

The RHS one is a 100 micron filter.
The middle one is a way overspecced FI fuel pump (puts out more pressure than you need so don't think about getting one).
The LHS one is a 10 micron filter.

It was only to illustrate the two filter setup you described above. (Plus of course it's car porn, which we all like to see).

 

[Tinster]

Great timing Alan-

I am reseaching a 100/10 micron filter system today.

I'm pretty sure the crud is entering my car from the gas
station tanks.

My tanks was removed, beaten to death with all types of
steel bits and hot water. I just checked with a light-
sand on the bottom of my tank again.

d

 

[Geo Hahn]

Dale --

Next time you get gas you might also fill a separate container (milk bottle if no one is looking, approved gas container otherwise) and see what if anything settles out of the gas.

Don't gas pumps generally have an in-line filter (sort of like an oil filter) to remove any sediment?

Could be your gas but I would suspect your tank. A sample jar might provide you a clue.

 

[Guest]

You could always clean up your carbs (get all that crud out) and totally bypass your gas tank by setting a 1 gallon gas on top of your firewall and run for testing purposes only off that can. A little risky but would tell you if your fuel lines or tank are crapped out.

 

[Tinster]

You could always clean up your carbs (get all that crud out) and totally bypass your gas tank by setting a 1 gallon gas on top of your firewall and run for testing purposes only off that can. A little risky but would tell you if your fuel lines or tank are crapped out.

I was thinking the same thing.

 

[AweMan]

What I got out of that article is, if you run a 10 micron filter before the fuel pump it will clog up rather quickly and cause cavitation in the fuel pump which will result in vapor lock and eventual pump failure. <span style="font-weight: bold">The recomendation is 100 micron filter before the pump {between the fuel tank and fuel pump} and 10 microns after {between the pump and carbs or F.I.}</span>

The Franz filter company makes a fuel filter that will filter out 0.1 Microns. Which in my opinion may be a little excessive. {plus, I might add this filter is slightly cost prohibitive} It would seem to me that this level of filtration would clog rather quickly given the condition our gasoline is in when delivered to the stations. {Especialy in P.R.} Going by what Dale said in a previous post about P.R. getting poor quality fuel or U.S.A. rejected fuel.

Underground tanks at service stations that have been around for years are in poor condition adding to contaminants in the fuel they deliver to the pump.

I always try to purchase fuel from a newer service station if possible. {even if the price is a little higher} {3 cents On 30 gallons = A buck .... No biggie!}

 

[MGTF1250Dave]

Aloha,

Aweman, I think you got it reversed. The coarse filter goes between the tank and pump to get the big chunks and not restrict fuel flow to the pump since the pump is generally gravity feed. This reduces the possibility of pump cavitaion from inadequate fuel flow. The finer filter goes between the pump and carburetors. The pump will pressurize the fuel flow through the filter and maintain flow to the carburetors. This finer filter should be placed somewhere convenient so it can be replaced or cleaned routinely since it will filter (trap) more "stuff". Filters tend to become more efficient the dirtier they get, that is the trapped material further restricts flow so smaller and smaller items are filtered out. This continues until eventually the filter is glogged and flow is stopped.

Dale, the photos you have posted of one your dirty filters seem to show it installed "back wards". The filters like that I've used have a flow direction indicator (an arrow) on one or both of the metal ends. The fuel should enter the end opposite of the mesh filter and the output end is on the end the mesh insert attached to. This allows the debris to collect in the glass tube and the fuel to be filtered before it exits. The way your filter is installed, all the debris is trapped inside the mesh filter, a much smaller area and it restrict fuel flow.

As others have suggested, the problem may be outside of your car. Before you begin to rebuild your fuel system, I would let a quantity of gas sit in a glass container for a few days to see what settles to the bottom.

Good luck.

 

[NutmegCT]

Dale - when you looked inside the tank, is there any evidence of rust in the fuel tank itself? It's gotta be coming from somewhere!

Tom

 

[AweMan]

Aloha,

Aweman, I think you got it reversed. <span style="font-weight: bold">The coarse filter goes between the tank and pump to get the big chunks and not restrict fuel flow to the pump</span> since the pump is generally gravity feed. This reduces the possibility of pump cavitaion from inadequate fuel flow. <span style="font-weight: bold">The finer filter goes between the pump and carburetors.</span> The pump will pressurize the fuel flow through the filter and maintain flow to the carburetors. This finer filter should be placed somewhere convenient so it can be replaced or cleaned routinely since it will filter (trap) more "stuff". Filters tend to become more efficient the dirtier they get, that is the trapped material further restricts flow so smaller and smaller items are filtered out. This continues until eventually the filter is glogged and flow is stopped.

Dale, the photos you have posted of one your dirty filters seem to show it installed "back wards". The filters like that I've used have a flow direction indicator (an arrow) on one or both of the metal ends. The fuel should enter the end opposite of the mesh filter and the output end is on the end the mesh insert attached to. This allows the debris to collect in the glass tube and the fuel to be filtered before it exits. The way your filter is installed, all the debris is trapped inside the mesh filter, a much smaller area and it restrict fuel flow.

As others have suggested, the problem may be outside of your car. Before you begin to rebuild your fuel system, I would let a quantity of gas sit in a glass container for a few days to see what settles to the bottom.

Good luck.

If you go back and carefuly re read my post I said the exact same thing.

 

[70herald]

A
If you have a high-performance fuel system, Marren Fuel Injection recommends that you incorporate fuel filters before and after the fuel pump. A low-restriction (coarse, 100-150 micron) fuel filter should be installed between the fuel tank and the fuel pump inlet to protect the pump from sediment. A fine filter (10 micron) should be installed between the fuel pump and the injectors to ensure that small particles of debris that make it past the fuel pump do not clog the injectors themselves.

[/color]

The problem is that the TR DOES NOT have a "high-performance" fuel system, or fuel injection for that mater.

Put a 10 micron filter in and you are going to have problems because the pump just does not create enough pressure to force the fuel through.

On a fuel injection system super clean is important because the fuel injectors have a tiny opening, work at fairly high pressure and even a very small bit of dirt will plug them up.
The carb fuel valve and jets are HUGE in comparison to fuel injectors.

Now if you really want a "high performance" fuel system, you could use an electric pump, and all these filters. However to get really satisfactory performance you need about 3 PSI at the carb. The low pressure electric fuel pumps will give about 4psi so that should be about right, however the best way to do this would be to use a slightly higher pressure fuel pump (~15psi) the filters and then a pressure regulator to drop the pressure down. That would give the most consistent fuel supply performance.

 

[DNK]

Dale needs to take a pressure check after all those filters. Would be an interesting test prefilter and apres filter results.

 

[MGTF1250Dave]

Aloha Aweman,

You are correct, I didn't read your reply carefully. As Emily LaTella would say, "Oh, never mind". I agree, the fine filter will clog quickly and either reduce or stop fuel flow.

 

[AweMan]

No problem Dave, Our minds don`t always agree with what our eyes see. Or is that visa versa haha. Ask any defense lawyer! :lol: I`m guilty as well.

 

[tony barnhill]

The big metal thing is a stainless steel fuel tank.
The little metal thing is the battery box.

The black thing under the fuel tank is a fuel cutoff switch - you really want one of these! My tank is baffled and has twin takeoffs - they meet up at the cutoff. Be aware that cutoffs for AN fittings are as rare as hen's teeth though.

There are three red things connected together under that.

The RHS one is a 100 micron filter.
The middle one is a way overspecced FI fuel pump (puts out more pressure than you need so don't think about getting one).
The LHS one is a 10 micron filter.

It was only to illustrate the two filter setup you described above. (Plus of course it's car porn, which we all like to see).

I only have one question: WHY?

 

[Guest]

Easy - here's the front end :laugh:

 

[tony barnhill]

AHA! Its important to show the reason for all those modifications as some of us are less mechanically inclined & might not understand there's a reason for every modification from factory.

With the stock carb setup, the stock fuel delivery system is absolutely capable of doing the job provided its in proper operating condition.

 

[Guest]

The whole story is in my sig - first line :wink:

And yes the stock fuel delivery system will produce plenty of gas - even for triples - if you dont have too much in the way of it...