924Board.org

B · Joined: 25 Apr 2006 Posts: 487 Location: Ohio

hey everyone,

I was checking a manual today as I was going over some fuel flow issues, and noticed a pre-pump fuel filter. I was not sure what year the manual was from (ebay find) so I was skeptical at first. However when I looked - there is a small canister maybe 1/2 the size of the one in the engine bay. It comes shortly after the line exits the tank and it attaches about 2-3" before the external pump. It is placed as it is shown in the manual.

I noticed someone had posted a note about 2 fuel filters in another post. but no mention of a part number or if replacing it helped. I wondered if anyone else has changed this filter or encountered it at all?

I know that we have to maintain a fairly high fuel pressure and did not want to stick "any old filter" in its place.

Any input would be greatly appreciated

thanks
Sean
("79 924 na)
_________________
1979 924 n/a
BAE turbo
5-speed snailshell

924RACR · Posted: Sat Apr 14, 2012 9:09 pm Post subject:

It's not actually a filter, just a baffle, apparently for sound...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Luvmy80-924 · Joined: 15 Mar 2012 Posts: 56 Location: PA

I agree with 924RACR, it is a baffle not a filter. But if your asking can it be done? I saved my 924 from sitting for almost 8 years from the previous owner. Needless to say the fuel system was a little dirty. A lot dirty really. There was a lot of debris in the tank, I flushed it multiple times but still had a lot of little chunks of rust or something. I was worried about hurting the HP fuel pump so I removed the factory fuel line and installed some new fuel line and a late model GM fuel filter inbetween the tank and the fuel pump. Car still runs great, when the fuel pump starts to whine, I change the filter and it quites back up.
_________________
1980 924 N/A Everyday Driver
1986 930
And now a 1980 931

B · Joined: 25 Apr 2006 Posts: 487 Location: Ohio

Thanks -

So this should not be a concern for fuel flow

Baffle -? I wonder why they thought a piece like that was necessary there - could it really be that loud?

As for the extra fuel filter that you added luvmy80-924, did you use any specific filter, or just one that had the 90-100(?) pressure capability?

I was kind of thinking about the extra fuel filter as a precautionary measure, but I did not want it to affect the flow from the internal pump to the external pump.

thanks again everyone
Sean
_________________
1979 924 n/a
BAE turbo
5-speed snailshell

Luvmy80-924 · Joined: 15 Mar 2012 Posts: 56 Location: PA

The FP can get a little loud, especially when there going bad or starving for fuel. I don't remember what the part number is but it's the same filter my 99 yukon (5.7 SFI) and I screw barbs in the ends. Haven't had a problem yet.
_________________
1980 924 N/A Everyday Driver
1986 930
And now a 1980 931

924-76 · Joined: 05 Jun 2006 Posts: 1489 Location: Ontario, Canada

Is this help?
http://www.924board.org/viewtopic.php?t=26508&highlight=fuel+filter
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1976 924 N/A ROW SOLD
1980 931S
1981 931 Part car RIP

B · Joined: 25 Apr 2006 Posts: 487 Location: Ohio

thanks everyone - that is most helpful

I will check with the local Porsche shop to see if that is something they can get

I found a fuel filter a summit racing that will handle up to 100psi and will filter to 5 microns. It is an in-line type and will clamp in place. It is about 2" x 5" - It is $17 - I will have to make sure I have the extra space there to fit it and not bend the hoses too much

It seem like it might be a nice piece of extra security for the external pump.

thanks again everyone for all of the input
Sean
_________________
1979 924 n/a
BAE turbo
5-speed snailshell

Ozzie · Posted: Sun Apr 15, 2012 10:46 pm Post subject:

on the suction side of the pump there is little pressure.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

B · Joined: 25 Apr 2006 Posts: 487 Location: Ohio

thanks Ozzie -

so if I add a filter there I could possibly go with a lower flow rate - maybe one that might be set up for a larger carb something with about 1/2 that flow rate?

thanks
Sean
_________________
1979 924 n/a
BAE turbo
5-speed snailshell

!tom · Posted: Mon Apr 16, 2012 2:35 am Post subject:

Not lower flow rate, but less pressure.

You don't want to put a filter before the pump, as this can starve the pump for fuel. The pump needs fuel in it to remain cool and lubricated.

The filter is there to protect the fuel injection system, not the pump. That's not to say that big chunks won't damage the pump.

You should clean the tank with the fuel pump disconnected rather than trying to filter crud out if you suspect the tank has chunks in it. Otherwise, if the tank is in good shape, the fuel filter will filter stuff out prior to the fuel coming back in the tank via the return line.
_________________
78 924 NA
5-lug

Ozzie · Posted: Mon Apr 16, 2012 8:36 am Post subject:

Generally all you need is a large mesh filter to prevent larger particles getting to the pump.
Pressure rating doesnt matter.
Large pressure and low micron filters for pre pumps filters are not necessary and can cause fuel starvation problems.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

B · Joined: 25 Apr 2006 Posts: 487 Location: Ohio

thanks Ozzie

that makes more sense - I was concerned about fuel starvation

Sean
_________________
1979 924 n/a
BAE turbo
5-speed snailshell