For my 1994 Bonneville SE:
2 years ago I used Dorman #800-153 (3/8" diameter steel tube with compression fitting) and a tube-bender to near-exact replace the rusted-thru high-pressure fuel-line coming out of the filter ... this worked well.

Now, the parallel Return fuel-line (same location, under the P.S. rear door) is rusted-thru (sometimes I can smell fumes), and, it looks like this Return-line steel tube diameter is a bit smaller than the 3/8" high-pressure line.

Can anyone confirm that the steel Return-line is 5/16" (under the P.S. rear door) ?

If the steel Return-line is 5/16" then I am thinking about using Dorman #800-154 (intending to cut-off 1 end of the beaded ends) to fit into the O.E. nylon quick-disconnect towards the rear (into the sender unit), along with Dorman #800-142 compression fittings for 5/16" tube diameter to splice into the OE steel Return-line that runs from the front.

Thanks for any info.

My Series 1 L67 equipped 95 had a 5/16" return. I would have to assume they wouldn't use any other size on your 94.

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95 SLE... a keeper. 241k miles. Low and Slow.
97 BMW 528i
98 Infiniti vq35'd i30: 13.3@104mph, 30MPG Hwy (RIP)
02 Jag X-type
03 BMW M5
05 Chevy Cobalt LS
07 Infiniti G35s 6MT (Sold)
07 Ducati Monster S2R 800 with DS1000 swap
83 Yamaha IT175K
72 Yamaha DS7: '74 RD250 swap, JL chambers

Info on dropping a 92-99: Here.

5/16 return line was used on all of the '85-'99 C/H-body cars I've seen.

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Boost addict


The Fleet:
'93 SSEi - Twincharged + manual Build thread
'97 Camaro - Top swap
'05 STS - V8, AWD, her DD
'92 Trofeo - Fair weather DD
'99 Montana - top swap 3800
'04 Sierra 2500HD - LLY Duramax

Current project:
Something cool, trust me.

Upcoming projects:
'92 Bonneville SSE
'87 LeSabre T-type
'67 LeSabre

Gone to greener pastures:
'84 Sierra Classic - Twin turbo 3800
'97 LeSabre - Top swap

RIP:
'86 LeSabre - pictures
'93 SE - L67

Thanks for the quick accurate info ... I am now going to order the Dorman parts #800-154 and #800-142.

OK, before confirming the source of the gasoline odor I ordered the Dorman parts ... yes, as described the fuel return-line parallel to the fuel filter is severely rusted.

Today I get the P.S. rear up in the air and crawl under to confirm the fuel odor location.

Turns out I find an ~ 3/8" length-wise split in the the rubber-connector for the other not-rusted line (the smallest-diameter vapor line) between the metal vapor line (from the front) into the nylon tube (going to the rear) next to the fuel filter.

With the engine running, when I put my finger over the split in the rubber connector, then no fuel odor.

This vapor line rubber-connector looks to be 2-diameter molded ... a bit wider on the nylon tube end than on the metal line end.

I have some sizes of typical vacuum hose,
but instead of trying to use a single diameter vacuum hose as a replacement
I am thinking of wiping some Permatex Form-A-Gasket#1 into that OE rubber-connector split.

Anyone have a better idea, or a part# for the 2-diameter molded rubber connector ?