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Fuel line size - 85 635 March build

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Jlc
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Fuel line size - 85 635 March build

Post by Jlc » Mon Sep 13, 2021 10:13 pm

I plan to replace the fuel lines from the pump to the filter as well as those leading to the filler. It appears to be 8mm and 12mm from realOEM - I assume that is ID. Any tips or other hoses I should get. Do you use regular hose clamps?
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hornhospital
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Re: Fuel line size - 85 635 March build

Post by hornhospital » Tue Sep 14, 2021 5:07 am

Fuel injection pressure rated hose ONLY. 8mm I.D./12mm O.D. is correct. Regular (screw clamp) hose clamps are ok. The ones with the formed thread rather than slotted threads are better for the hose.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann";'87 325is "Odette"; '93 325is "Elvira"; '95 M3 "Ashlyn"; '95 318is "Bebe"

Jlc
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Re: Fuel line size - 85 635 March build

Post by Jlc » Tue Sep 14, 2021 10:35 am

Thanks. I had mistakenly assumed there were 2 different sizes.
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anchored
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Re: Fuel line size - 85 635 March build

Post by anchored » Tue Sep 14, 2021 1:42 pm

I used 5/16 because it was cheap and I am a sinner.
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Ralph in Socal
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Re: Fuel line size - 85 635 March build

Post by Ralph in Socal » Tue Sep 14, 2021 4:36 pm

Jlc wrote:
Tue Sep 14, 2021 10:35 am
Thanks. I had mistakenly assumed there were 2 different sizes.
You’re not mistaken. 8 mm ID FI hose mostly except for the 12 mm ID line from the tank port to the inlet on the external fuel pump. About 2 feet long but varies a small amount based on model year. This line is not under FI pressure so just good quality fuel line is adequate. A bit difficult to replace the line as it snakes between the body and the fuel tank. Loosening the tank mount bolts and allowing the tank to lower a little bit helps a lot

Ralph
There is a very fine line between "Hobby" and Mental Illness.

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84 528i Euro
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Jlc
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Re: Fuel line size - 85 635 March build

Post by Jlc » Tue Sep 14, 2021 5:06 pm

Ralph,

Thanks. I plan to replace all the lines back there while I'm at it.

It's maintenance month - new belts, oil, filter, a few cracked lines, CV Boots or possibly entire axle assemblies, pittman arms (dogbones), sway bar linkage. Good news trans fluid is fine. May do radiator hoses while at it and flush..
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Re: Fuel line size - 85 635 March build

Post by Jlc » Thu Sep 23, 2021 8:10 pm

Ralph, Any idea how much of the High Pressure 8mm line I need?

Thanks,
Jim
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Re: Fuel line size - 85 635 March build

Post by Ralph in Socal » Sat Sep 25, 2021 4:38 pm

8 mm ID under the hood is about 3 feet. Don’t forget “the little perisher” (ode to Brucey) hose that feeds the Cold Start Valve.

Another 2 feet or so by the fuel pump and filter assembly. The return lines (about the same lengths) are not under FI pressure so good quality fuel lines are fine.

Ralph
There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
84 528i Euro
83 635 Euro Arktik
81 528i Kastanien 5-speed
88 528e Bronzit (Granpa Car)
86 535i Auto (For Sale)
81 633 csi (retired)

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Re: Fuel line size - 85 635 March build

Post by Jlc » Sat Sep 25, 2021 11:16 pm

Thanks. Under hood looks good but will double check.
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