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Unread 09-17-2009, 12:30 PM   #1
Augy
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Fuel Filter and return line question 4.2L

This might be a dumb question but,... that should be my tag line :-)

I installed the weber carb awhile ago and everything went fine, runs like a champ. I finally got around to cleaning up all (or most) of the excess vacuum lines, pulse-air crap, etc. I noticed my fuel return line (I think that's what it is) was just capped off. I vaguely recall doing this I think because I had a generic fuel filter with only one inlet and one outlet.

Do the stock filters have an additional port for the return line? If so should I get a stock filter and plumb that return back in, leave it capped, or something else? It looks pretty lame as it is so I'd like to clean it up a bit.



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Unread 09-17-2009, 12:36 PM   #2
kgillette
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the stock filter does has two outlets.

benifits of having/removing the return line I cannot tell you.
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Unread 09-19-2009, 06:42 AM   #3
Augy
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Thanks, I may just replace my filter with a stock one. Anyone else have advice or a suggestion?
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Unread 09-19-2009, 08:00 AM   #4
zeus87gn
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Yes, you need the stock filter wth the dual outlet. It's like a presure relief valve for the fuel pump. If the pump is sending too much fuel to the carb, the float valve will stop the flow of fuel into the bowl. If that return line isn't there, the fuel has no where to go. This could possibly rupture the diaphragm in the fuel pump...depending on the quality of the pump. If that ruptures, you have a direct fuel leak into the crankcase. And that is BAD.

This situation is even worse with the Weber, or most aftermarket carbs. The Weber needs about 3-4 psi (if memory serves) and the stock pump puts out about 7-8 psi. Many here (including me and my Holley) have found that running a fuel pressure regulator allows beter tuning. And you would need the dual outlet filter even more if you were to put the regulator in.

HTH,
Z
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Unread 09-19-2009, 08:51 AM   #5
Augy
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Ok, thanks for that explanation. I do have the Holley FPR installed. I'll go pick up a stock filter today and plumb it back in. Hopefully, I haven't done any harm as yet.
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Unread 09-19-2009, 10:57 AM   #6
Augy
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I need some more help I can't find where the stock filter would have been. My Haynes manual says it's on the left frame rail near the fuel tank but there isn't one back there. The generic one I put in was in between the FPR and the carb.

I got a new stock filter and tried it where the generic one was, and plumbed the return to the metal tube in front of the carb. When I started it, I could tell the fuel was pulsing between the FPR and the Fuel Pump. Also, the FPR pressure guage dropped to 2 psi (from 3.5 before). I tried adjusting it but it doesn't seem to want to change.

Does the filter (and it's return line) need to be plumbed before the fuel pump? Could that be the problem? Thanks.
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Unread 09-19-2009, 11:07 AM   #7
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Miine is right befor the carb inline with the primary line keep the return line high so it dosen't drain back to the tank.

Dwayne
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Unread 09-19-2009, 11:08 AM   #8
Augy
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This is what I have plumbed right now...

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Unread 09-19-2009, 11:18 AM   #9
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That is a butt load of fuel line but it looks right.I would insulate the lines so you don't vapor lock.

Dwayne
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Unread 09-19-2009, 11:29 AM   #10
Augy
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I should probably move the FPR and filter to the other side and just have one longer fuel line from the pump to the FPR.

I am still only getting around 2 psi out of the FPR and it doesn't seem like I can adjust it. It's also pulsing pretty wildly. Sonmething isn't right...any ideas?
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Unread 09-19-2009, 12:09 PM   #11
4.7stroker
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With the return line you will not build up pressure, I run the return line without a FPR but I am also running the Motorcraft MC2150. I don't know if this will work with the Weber but I don't see why not.

Dwayne
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Unread 09-19-2009, 12:37 PM   #12
zeus87gn
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Your FPR needs to be between the filter and the carb.
Right now your FPR is between your pump and the filter.

Here's my setup....
p2130208-.jpg  
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Unread 09-19-2009, 01:33 PM   #13
Augy
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I wondered about that (having the FPR after the filter). I replumbed things and got rid of a bunch of line and moved the filter to before the FPR. I haven't run it yet...spilled a bit of fuel and think it best to let it evaporate! I'll run it later today and post back. Here is a pic of the new setup:

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Unread 09-19-2009, 03:50 PM   #14
zeus87gn
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Ah yes!
Much cleaner looking.
You should have it set up now to get it tuned just right.
I may have missed it but you do have it bypassed, right?
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Unread 09-19-2009, 04:46 PM   #15
Augy
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Yes, I did the nutter bypass before I swapped carbs. I just went out and fired it up. Still have the pulsating and my FPR isn't adjusting the psi. The guage is bouncing around at about 2 psi. I can see and feel the the fuel line from the pump to the filter pulsing as well.

It was running fine before. The only change is I plumbed the fuel return back into the system and put in a stock fuel filter. Any ideas? Thanks again.

Last edited by Augy; 09-19-2009 at 04:59 PM..
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