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Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 6:59 pm
by purplehaze
A little help please -
1967 1600 with SU carbs
started up, rough idle after ~2 weeks sitting, almost as if missing 1-2 cylinders
smelled gas while warming it up, immediately shut it off, saw gas on top of the carb, in back of the fuel inlet, near what I think is the broken fuel return line (the one on the left)
I honestly don't remember if it ever had an unbroken line, as its always worked, never leaked
- if the carb was clogged, would it back up excess fuel through that line?
- any ideas where to source a replacement line? I haven't seen this version with the metal return lines available anywhere
It's since cleared itself up, and won't repeat itself. I removed the banjo fitting, it runs fine, with no fuel being returned through that fitting or opening even when rev'd up
My confidence in going for a longer ride is reduced, and yes, I've readied my fire extinguisher just in case
Thoughts or suggestions appreciated!
Thanks -
Glenn
IMG_3634.jpeg
IMG_3633.jpeg
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 7:29 pm
by Habitat.pat
The broken off lines are not return lines, but overflow lines. They ran down to end below the block & exhaust, by the oil pan. I thought the lines were shown in the parts Fischer but I couldn’t find them. There is also a small metal support to hold the bottom of the lined that mounts with one of the oil pan studs.
Peace,
Pat
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 7:40 pm
by purplehaze
Thanks, Pat, good to know
I guess mine never overflowed, until now
Wonder why
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 7:47 pm
by DAC21
purplehaze wrote: Sun Feb 27, 2022 6:59 pm
A little help please -
1967 1600 with SU carbs
started up, rough idle after ~2 weeks sitting, almost as if missing 1-2 cylinders
smelled gas while warming it up, immediately shut it off, saw gas on top of the carb, in back of the fuel inlet, near what I think is the broken fuel return line (the one on the left)
I honestly don't remember if it ever had an unbroken line, as its always worked, never leaked
- if the carb was clogged, would it back up excess fuel through that line?
- any ideas where to source a replacement line? I haven't seen this version with the metal return lines available anywhere
It's since cleared itself up, and won't repeat itself. I removed the banjo fitting, it runs fine, with no fuel being returned through that fitting or opening even when rev'd up
My confidence in going for a longer ride is reduced, and yes, I've readied my fire just in case
Thoughts or suggestions appreciated!
Thanks -
Glenn
IMG_3634.jpegIMG_3633.jpeg
I don't blame you for keeping the car close to home + fire extinguisher. With non-existent over flow tubes that is an engine fire waiting to happen.
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 7:59 pm
by Nissanman
PLEASE fit new rigid lines to those overflows to avoid gas spilling over the hot exhaust
They need to vent at or below the engine sump level.
Here is a good picture of what they need to be like: -
G15 engine.jpg
As for the fuel venting out the overflow, mine did that not long after getting it back on the road.
Found a tiny bit of fluff jamming the float valve open
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 8:00 pm
by cbez
the float needles like to jam open.
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 8:10 pm
by purplehaze
Thank you very much DAC21, cbez, and Nissanman!
Yup, I'm going to order a rigid replacement tube, not that I know what to call it. I guess I'm lucky it didn't overflow previously, yikes
Might be time to remove and clean the carb/needles/float.....
Thank you !
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 9:10 pm
by cbez
clean any crud out of the fuel bowl. I like to put an extra modern filter in between the old filter and the pump like K&N 81-0221
if you have any crud in your pump it could still go to the carbs tho.
pic from the facebook group:
any one of those lil specs could have the float bowl pissing gas
Re: Fuel leak - SU carb, any ideas?
Posted: Sun Feb 27, 2022 9:10 pm
by spl310
I'm betting sunken float.
Re: Fuel leak - SU carb, any ideas?
Posted: Mon Feb 28, 2022 8:02 am
by jrusso07
A quick check on float level/fuel level in the bowl is to remove the dome and piston and observe the fuel level at the jet. It should be just a little puddle barely covering the jet orifice. The level at the jet is the same level as in the fuel bowl and it is set by a combination of the float setting and the jet height (static positioning and fuel richness setting)
Re: Fuel leak - SU carb, any ideas?
Posted: Mon Feb 28, 2022 5:38 pm
by TobyMan
I was wondering what those riged overflow lines were for. Glad I was trolling and saw that. A picture too! This forum is the best
Re: Fuel leak - SU carb, any ideas?
Posted: Mon Feb 28, 2022 7:05 pm
by purplehaze
Thanks Joe and spl310 !
Ordered fuel overflow line, and going to tear in to see what I find....
Re: Fuel leak - SU carb, any ideas?
Posted: Tue Mar 01, 2022 2:08 am
by jhayden
spl310 wrote: Sun Feb 27, 2022 9:10 pm
I'm betting sunken float.
And, if they are the original brass, better to replace with these:
https://www.datsunparts.com/1628
Re: Fuel leak - SU carb, any ideas?
Posted: Tue Mar 01, 2022 1:25 pm
by Gregs672000
TobyMan wrote: Mon Feb 28, 2022 5:38 pm
I was wondering what those riged overflow lines were for. Glad I was trolling and saw that. A picture too! This forum is the best
I've learned a lot by reading most every post, even if it's not strongly related to my car or an issue I'm experiencing... probably will at some point! And I agree, this group is amazing. It's awesome what humans can do when we just get along and work together. This may just be a car site, but the spirit is the same.
Re: Fuel leak - SU carb, any ideas?
Posted: Tue Mar 01, 2022 2:39 pm
by spl310
While the long tubes of the originals were cool, they are prone to breaking if you don't have the oil pan brackets and washers. Honestly, the short ones with tubing attached to them and routed to the suspension side of the frame is much better.