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-   -   1.7 Fuel Filter (http://forums.pelicanparts.com/porsche-914-914-6-technical-forum/228-1-7-fuel-filter.html)

Gonzo 07-08-1998 05:52 AM

1.7 Fuel Filter
 
Hey Guys,
I was checking the fuel pump the other day & noticed a generic fuel filter like the ones used in VW Bugs on my 71 914, probably put on by the PO. My question is does it effect anything by using this type of filter or should I get the one listed in the Haynes manual?

Dave at Pelican Parts 07-08-1998 07:21 AM

If your car is fuel injected, do not use the generic Bug filters. Those are appropriate for low-pressure and low-flow carb-oriented fuel systems, but are not strong enough for the stock fuel injection's fuel supply system.

Get the big square one if you've got FI. The filters come in two different styles. One has two 7mm fittings on it, while the other has a 7mm and a 9mm. ("Little-little" or "big-little".) Check your hoses to see which one you need.

--DD

JP Noonan 07-08-1998 12:44 PM

Dave is right, you can rupture the low pressure type of filters, designed for 4-7 PSI when used on a FI engine reaching 30-40 PSI. I redid ALL my fuel lines, but could only fine SAE lines at the time 5/16 and 3/8" are close to 7mm and 9mm. The filter I ended up using came from a late 90's Jeep. It may not fit in a factory setup but it is huge/has great flow and has two 3/8" openings. If you still have factory lines then use the factory filter, I only modified mine because the NAPA I worked at had that other filter in stock.

Tim Polzin 07-13-1998 11:36 AM

Did I miss something? Isn't the fuel filter on the suction line from the tank?

Dave at Pelican Parts 07-13-1998 04:15 PM

No, you didn't miss anything. The low-pressure side of the pump is where the filter usually goes.

The whole fuel system in the 914 flows a whole lot of fuel, though. In a carbed car (if I understand correctly), the pump only pushes enough fuel for the engines actual use, more or less. In a fuel-injection system like the 914 uses, there is quite a bit more fuel flowing than the engine uses. This is done for a lot of reasons, including making sure that there is enough fuel under ALL circumstances, keeping the fuel cooler than if it were just sitting on top of the engine, and even cooling the fuel pump.

However, the Bug filter is both low-pressure AND low-flow. The high flow required of the stock FI system may be too much for it, especially over time.

I'm not sure what the actual pressure on the low-pressure side of the pump is, but I wouldn't be surprised to see a number somewhat higher (or even lower due to the suction) than the Bug filter was designed to cope with.

The bottom line is that fuel leaks are VERY bad things. (Unless you want to burn your car to the ground, possibly with yourself in it.) It's probably not worth saving the $10 (or whatever) buying cheapo Bug filters that weren't designed for the stock fuel injection.

--DD


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