Leaky Fuel Filters

[FJCamper]

We use clear plastic fuel filters on our racers so we can see fuel color, movement, and whatever debris might be trappped in them at the time. It is a bit humbling to be using the same filter as light garden equipment, but they work, and pass enough fuel in volume to sustain the 2.2 Blitzwagen hours on end in a LeMons enduro.

We also go through a lot of these, as well as FLAP "rubber" fuel line, as heat and ethanol-diluted gas harden the lines. No kidding. We change all the fuel lines, and the three filters about twice a year. That's one each filter for the Kads, and one exiting the fuel cell to the fuel pump. The same is true on our Historic Sportscar Racing Ghia.



Anyway, a leaking disposable filter was a rarity for us, until we bought a box of 10 from Amazon (link above) and the first five we tried out of the box failed. We did some minor forensics and discovered uneven gluing around the filter joint. The photo above even shows a build-up of glue dyed orange (we think) by the paper filter. We had mostly Sunoco racing gas in the Ghia, the grade of which is undyed.

We even wondered if the racing fuel was affecting the filters, or if the fuel pressure (3.5psi for the Weber's) was a contributor. But the buyer's comments on Amazon told it all. Customer after customer had the same experience as us.

The point here is no matter the brand, come back and check your clear plastic fuel filters after an hour or so, no matter what the brand.

FJC

PS: We tried hot glue and Super Glue to 'make these defective filters usable, but no luck. Drip, drip, drip ...

[sideshow]

I only use those in gravity feed places like mowers/small engines, never though much of them in automotive use. They fail there also. When young I used them as size adapters to make the conversion from metric to SAE and back but stopped after finding non-V8 bits.

The glass screw together type that the internet seems to hate have all ways worked fine for me. Zip tie or adel clamp the body and easy to clean.

[FJCamper]

Hi Sideshow,

I wouldn't subject clear plastic filters to anymore than 3 to 4 psi. Having this batch of leaky filters gave us a chance to experiment with pressures.

If you put a vac/pressure pump (with gauge) on the inlet side and block the outlet side, you can see exactly where the seams pop as you pump.

20 psi will dramatically blow any of them, guaranteed. some fail at 8 psi, most hold to 10 or thereabouts.

I still have one of the original Pyrex glass, metal filter element screw-together in-line filters in my tool box, a leftover from the past. I stopped using it because of the possibility of leakage.

FJC

[Piledriver]

I like big metal filters . Cheap, available, and last for ages.
Preferably up by the fuel pump, under the tank. properly secured.

I admittedly don't race, but I am lazy, and would rather do it once.

The CIS filters are huge, work well, and are rated for ~300 PSI.

[66brm]

I'm with pile on this one, I've started converting over to injection rated big filters like the vanagon ones even for my carbed cars, never had an issue since

[Dale M.]

The conundrum here is it is nice to see the fuel flow or sediment build up in filter VS. the reliability of solid metal filters... For reliability the metal canister all the way....

A filter with metal body and replaceable elements so you can still do inspections might be best......

Dale

[Piledriver]

It would be easy to replace the glass cylinder on one of the "see through" units with metal tubing to allow easy inspection.

One would need to replace the orings regularly tho, and probably figure out how to safety wire it so it cannot unscrew.

FI fuel loops have huge filters as they are continuously circulating huge volumes of fuel.
They tend to keep the fuel system sparkly clean due to that continuous filtering.

[FJCamper]

To explain our use of small clear plastic lawn mower fuel filters (and we plea we are not asking for forgiveness, just understanding) here's our case in a nutshell.

Penske is famous for his phrase, "the racers edge." Not to exaggerate, but every minute off the track hurts badly. Example, once we had a sudden and inexplicable failure to start after a refuel. We don't have a fuel pressure gauge on the dash because our drivers have enough on their minds to just watch the tach (sometimes) and the big fan belt and oil pressure lights on the dash. Plus, most sanctioning bodies forbid fuel pressure gauges fed by a fuel line of any sort, metal, braided steel, or rubber for fire safety reasons. Electric gauges are permissible , but a sensor and gauge cost about $150 or more USD better spent elsewhere on the car. There is a cheaper electric fuel pressure sensor kit that turns on an idiot light as long as pressure exists at whatever pickup point you chose.

Anyway, we see no fuel in the carb filters, and run forward to the filter between the fuel cell and fuel pump. No gas! The electric fuel pump is running, but no fuel is being pumped. We twist off the big circle-track style fuel filler cap and run a hand down inside, pushing the foam blocks aside, and pull up the fuel pickup wire mesh cage.

No obstructions! Then a brain cell kicks in and the mechanic twists the rubber flex line on the fuel cell's top plate and it moves. The FLAP guaranteed synthetic fuel line had swollen and expanded and was sucking air just above the fuel level.

We fixed it with a new hose.

FJC