Fuel rail return line fitting

[Jack B]

My return line connector on the stock 86 fuel rail is weeping. I purchased new dorman 1/4" duckbills and it's even worse now. I make sure the rail was clean. Hit it with some fine sandpaper but no luck. I have a constant drip when the car is running and a weep not running but under pressure. I am adjusted at 43.5psi.

Inspected the connector and didn't see any apparent damage. Do the connectors ever "go bad" whereby the clip doesn't seal properly?

[MikeFleming]

The seal is by two parallel o-rings between the inside of the connector and the metal part of the rail tube end where the hose tube end fitting pushes over. Are you sure your leak is from the return line? It is not under any measurable pressure, especially with the pump(s) off. Here is an an assortment of pics.

Square intake (85.5/86 SVO) fuel rail tube ends. These should be almost polished, 600+ grit finish. Return on right side of pic - it's noticeably smaller.
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Left side is the 5/16-5/16 pressure line fitting with the external retaining clip; right is the 5/16-1/4 return "Duck Bill" fitting.

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Duck Bill fitting and release tool.
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Duck bill fitting w/o release tool. Note sealing o-rings.
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Release tool inserted into Duck bill fitting - note sealing o-rings.
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Pressure side fittings. Note o-rings.
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Left - SVO style (era) 5/16-5/16 pressure side fitting; center - later model (1990+) pressure side 5/16-5/16 fitting; right - 5/16-1/4 return Duck bill fitting (SVO era)
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Same as above side view with retaining clips removed. NOTE the center tune end will NOT fit the SVO fuel rail properly.
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Installation to in-tank fuel pump.
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[Jack B]

Hey Mike,

Yep. It's the small return side. I have gas all over my fingers as I "probe" around. The connector gives an audible click when engaged on the rail and will not disengage without using the tool. The pressure side is fine. It's leaking enough that fuel pressure gauge drops to 25 within just a few mins. There is no pitting nor crude on it. Guess I will have to remove the rail for closer inspection.

Do these connectors ever go bad?

[Jack B]

Hard to tell but it appears that the o-ring is damaged in the connector.

[MikeFleming]

Yes, they can go "bad", not quite like Breaking Bad though.


Hard to tell but it appears that the o-ring is damaged in the connector. Assuming you installed a new 1/4 fitting versus a 5/16 one, I wouldn't expect it to leak as new o-rings do pretty well as far as sealing on the metal tubes; whereas installing a 5/16 end would definitely leak from the get-go. I would replace it again. BTW - stop running the engine until that's fixed (DO NOT drive it). Fuel fires are not as much fun as they sound.

For the new one. moisten the o-rings with some rubbing alcohol (it's VERY slippery, leaves no residue and will burn just like petrol) before installing it onto the metal tube. I always have a small squirt bottle of it in the shop for assembling all kinds of hoses to tubes (radiator, coolant hoses, etc.).

Remember: You heard it first.

BTW - any/all pressure loss is either due to the check valve in the pump or the regulator leaking. The fuel return lines are not responsible at all for holding any pressure. It's only job is to return whatever fuel goes past the FPR back to the tank.

Normal system pressure will dop to 25-30 instantly when the pump(s) are switched off. Then - for a good system- will stay above 20 PSIG for 10 minutes, above 10 PSIG for 20 (total). If it bleeds down faster, that can lead ot hard starting when hot. FPR and fuel pump check valve are the likely culprits (and sometimes the in-tank S hose with single pump systems). Other than that, the only other place for pressure loss is a leaking hose or fitting.

[Jack B]

Thanks Mike. I am not driving. This is first startup on a new combination.

Guess I didn't explain correctly.

I only replaced the 1/4 duckbill clip. I am getting a new connector tomorrow.

The pressure loss is as you stated. It goes to about 25 almost instantly but stays above 10 for an hour. I was surprised at the amount initial loss.

The pump and regulator are brand new with zero miles.

[MikeFleming]

I only replaced the 1/4 duckbill clip. I am getting a new connector tomorrow. Makes more snese now. Time to replace the fitting.


The pressure loss is as you stated. It goes to about 25 almost instantly but stays above 10 for an hour. I was surprised at the amount initial loss. Yep, that's expected so NPF (no problem found).

[ChrisCurtin]

Crap. Are there o-rings in all the connectors on the fuel lines? I just finished running everything (new tank) and don't remember seeing any o-rings in any of the connectors (tank feed/return, fuel filter in/out rail connectors)

Are they all the same size? Any part #'s I can look up? A quick RockAuto and AutoZone search didn't list any 'fuel line o-rings'.

Thanks,

Chris

[MikeFleming]

Are there o-rings in all the connectors on the fuel lines? If not all fittings will be leaking. Especially the pressure side. The o-rings inside the fittings are the only seal.



Are they all the same size? Any part #'s I can look up? A quick RockAuto and AutoZone search didn't list any 'fuel line o-rings'. Might be for same fitting, same mfgr, same run design. But the 5/16 fitting seals are not the same as the 1/4 fitting seals, obviously.

I have never been successful in replacing the o-rings in the fittings. And do not know any source for just the o-rings. Just replace the end fitting on the return line. Simple enough. With the proper took, you won't need to remove the tube/line from the car.

Suggestion: Test fit the new end fitting onto the fuel rail and verify it has a correct fit before installing it on the tube end.

The "repair kits" (fitting end, w/attached 18" tubing, coupler) are readily available many places. RockAuto should have the fittings (ends) but will not have the internal o-rings. I think you want Dorman 800-053 ( http://www.jegs.com/i/Dorman/326/800-053/10002/-1 )

Note that you will want (need?) to take the 18" tube section off the barbed end of the fitting to install it onto the end of your existing tube. be VERY careful to not damage, smoosh, dent, etc. the sharp barbed edges of the new fitting when you cut off the extension tubing. Those barbs are important to maintain a leak-free join to the tube end.

Alternately get just the end fitting (less available than the repair kits though).
Amazon: http://www.amazon.com/Dorman-800-083-Fuel-Line-Connector/dp/B000E3021A#productDetails

O'Reilly: http://www.oreillyauto.com/site/c/detail/DOE0/800083/N0044.oap?ck=Search_N0044_-1_-1&pt=N0044&ppt=C0052

Jegs: http://www.jegs.com/i/Dorman/326/800-083/10002/-1

[Jack B]

All fixed. Used Dorman 800-053 & 800-191.

thanks

[MikeFleming]

Party On, Wayne!!

[ChrisCurtin]

Sorry to hi-jack.

Here are the lines at the fuel rail on my 84 Capri RS Turbo. No rubber o-rings. From what I remember all the other connectors had the white hard plastic in them only (I inspected them for nicks, wear etc. and all looked good before assembly.)

Should there be o-rings like in the pictures above (orange and/or yellow)?

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Thanks,

Chris

[MikeFleming]

Yes, there are o-rings but they're not rubber - viton is more likely. Gray/dark brown in your pic. We haven't used real rubber in fuel systems is >35 years.

See arrows in attached pic. Gray/dark brown in your pic.
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