Fuel Filter backward?

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MR - 03 Dec 2007 00:42 GMT

1990 740 GL:

I was replacing the fuel filter, and made a point to note the
orientation of the current filter before removing it. However, the new
filter has a "FLOW" arrow which, if I install the filter the same way as
the current filter, will be pointing toward the rear/tank. This seems
wrong, obviously.

Is it possible my filter has been backward for 60k miles? Can the car
even run with the filter installed backward? Was I getting any fuel
filtration all those miles if it was installed incorrectly?

The filter canister has a rim on one outlet end (based on the flow
arrow), and is smooth on the input end. Which way does it go?

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James Sweet - 03 Dec 2007 06:10 GMT

> 1990 740 GL:
>
[quoted text clipped - 10 lines]
> The filter canister has a rim on one outlet end (based on the flow arrow),
> and is smooth on the input end. Which way does it go?

If it's the same as my '87 then this is how it's supposed to be. Fuel flows
from the tank into the back end of the pump, and then out the front of the
pump into that end of the filter and out the back, where it loops around
again to flow to the engine.

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auto467016@hushmail.com - 03 Dec 2007 18:55 GMT

> > 1990 740 GL:
>
[quoted text clipped - 15 lines]
> pump into that end of the filter and out the back, where it loops around
> again to flow to the engine.

I looked at the old filter -- it too had the arrow pointing toward the
*rear* of the car when it was installed. Very strange.

I installed the new one the same way (arrow toward rear), and the
car's running fine. I may get back under the car to follow the lines
to confirm what you've described, but I'm pretty confident that it's
installed correctly.

Thanks!

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James Sweet - 03 Dec 2007 19:21 GMT

>> > 1990 740 GL:
>>
[quoted text clipped - 23 lines]
> I looked at the old filter -- it too had the arrow pointing toward the
> *rear* of the car when it was installed. Very strange.

Why is that strange? That's the direction the fuel flows, follow the lines.
Like I said, it comes from the rear towards the front to go into the pump,
comes out of the pump facing the front of the car and loops back towards the
rear through the filter, it then loops back around towards the front. Since
the pump and filter are side by side, it has to change directions anyway.

On second thought, you may have the Regina fuel system with a single in-tank
pump, I've never worked on one of those, but I suspect they retained some of
the same plumbing and bracketry from the more common Bosch system.

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auto467016@hushmail.com - 03 Dec 2007 23:13 GMT

> <auto467...@hushmail.com> wrote in message
>
[quoted text clipped - 41 lines]
> pump, I've never worked on one of those, but I suspect they retained some of
> the same plumbing and bracketry from the more common Bosch system.

No, I've got the Bosch fuel system.

I guess once you start thinking about how the pump and filter are side-
by-side, it doesn't seem so strange to have the "Flow" arrow pointing
toward the rear of the car. It just seemed counter-intuitive to have
the "Flow" arrow pointed away from the engine and back toward the
tank. But again, once you consider the pump and filter positions
relative to each other, it starts to make more sense.

Again, thanks, I'm pretty sure it's installed right and the car's
running smooth.

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James Sweet - 03 Dec 2007 23:27 GMT

> No, I've got the Bosch fuel system.
>
[quoted text clipped - 7 lines]
> Again, thanks, I'm pretty sure it's installed right and the car's
> running smooth.

Those filters are used in a zillion different European cars. The arrow
indicates flow through the filter, not which way the filter points relative
to where the fuel eventually ends up. In K-Jet Volvos the filter is
transverse so the arrow points to the side of the car when installed.

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Stephen Henning - 03 Dec 2007 14:19 GMT

> I was replacing the fuel filter, and made a point to note the
> orientation of the current filter before removing it. However, the new
> filter has a "FLOW" arrow which, if I install the filter the same way as
> the current filter, will be pointing toward the rear/tank. This seems
> wrong, obviously. [1990 740 GL]

Use the arrow as a guide. The new filter may be built different from
the old one. If the old one doesn't have an arrow, it may work in
either direction. Many do work in either direction.

I once got a tank of bad gas in NC which had sand in it. Luckily my 240
had a fuel filter so it didn't damage the engine, but it kept clogging
up the fuel filter and quitting. I had to limp to a station where I
could get it fixed. So, when the car wouldn't run any further, I
disconnected the fuel filter and just connected it backwards to the tank
side and pumped enough gas through it and onto the ground to clean the
filter. Then I reversed it so it was the right direction, did the same
then and then hooked it up. This would get us another 20 miles. I
finally got to a gas station where they removed the fuel tank and
cleaned it out. Then I used a new fuel filter a couple weeks before
replacing it. It never did damage the engine or the fuel pump.

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