Carb Leaking Gas
Created by: Dharmapunx614
Found 30 Messages
That just saved me a bunch of time in trial and error...Thank you Malsal!
Slowly, but surely I'm going to sort all these niggling things (like my newly intermittently leaky rear wheel brake cylinder - although I'm pretty sure I've got that covered since I've done that kind of work before)
All the best, Jim
It fits on the drip rail and faces upwards sealing against the hood.
If in doubt, flat out . Colin Mc Rae MBE 1968-2007.
There's supposed to be a "rubber seal that sits along the rear edge of the hood"????
Yeah...I ain't got that for sure Malsal!
Looks like I need this one: http://www.minimania.com/web/Item/JRC7008/InvDetail.cfm
Does it fit onto the top of the small square channel wall that is part of the scuttle (and squish upwards against the hood) or does it fit somewhere onto the bonnet itself and squish downwards onto something else?
This might totally explain my mystery water in my driver's footwell after our "moonsoon in NYC" weather a few weeks back if it overflowed and ran in and down through the holes in the firewall/bulkhead where the clutch and accellerator go through... (see http://www.minimania.com/web/threadid/106460/msgthread.cfm)
While I'm at it I think I should pick up these two other seals as well: http://www.minimania.com/web/Item/JRC7898/InvDetail.cfm & http://www.minimania.com/web/Item/BPF133%2F4/InvDetail.cfm.
Thanks so much!
If you are missing the rubber seal that sits along the rear edge of the hood opening water will run over the small lip into the engine bay.
If in doubt, flat out . Colin Mc Rae MBE 1968-2007.
It would be nice if it didn't touch the foam. I find it hard to imagine that the carb corroded through, but who knows what some folks might get up to.
I can see how any one of those things could shift a motor backwards, but I don't believe any of those things are the case (but then I really don't know the history of the car that well, seeing as how I've only recently bought it).
The manifolds look stock to me, alloy on the intake and cast iron to the two downpipe exhaust. But it does have the thicker black "phenolic" (a fancy word for plastic) spacer (like this: http://www.7ent.com/products/carb-spacer-hs6-hif44-6mm-thick-610849.html )...maybe that is why the carb comes so far back? (see my avatar - you can enlarge it by pressing Ctrl and "+" a bunch of times; Crtl and "0" to rever to normal view)
But the carb does NOT hit the firewall/bulkhead, in fact it has about an inch in clearance one the foam was removed and when you apply the brakes and clutch it and bring it into gear, the motor doesn't rock at all, so I think my mounts are sound.
Are you saying that, under normal circumstances, the carb should not make contact with the foam pad AT ALL?
As always any and all advice is MOST welcome!
Are the engine mounts perished? Is the intake manifold wrong for your car? Do you have some incorrect parts in there?
Just wanted to report on what the leak REALLY was from...
In my Mini, there is a thick foam pad on the firewall behind the carb. The carb squishes into this from about the point at which the float chamber lid meets the body if the carb (at the seam) and then the foam expands back out underneath the carb to press against the little bump on the bottom of the float lid (where the bottom of the "L" shaped jet extends down to inside the float chamber).
Well that foam must trap water or condensation because it appears that the float lid had pitted through right on the bump.
Or at least that is my guess because the previous owner had slathered brown epoxy all over the outside of the bump on the lid and you could see an extrusion of it inside the lid. It was just a matter of time after I bought it before the gas ate through the bond between the epoxy and the lid.
A new float chamber lid and O-ring from Joe Curto (a spectacular SU carb guy in Queens - see http://www.joecurto.com - I highly recommend him) and I am all fixed! No leaks anymore.
BTW, it is possible to JUST remove the vacuum hose, and the three other hoses (fuel in, overflow/float vent & crankcase ventilation) and you can get away with rotating the carb upside down to replace the lid without having the time consuming task of removing and then putting back and re-adjusting the accelerator or cold start/choke cables AS LONG AS you also slip the plate that they are attached to off the manifold bolts and move it along with the carb.
But don't forget to check the dashpot oil after the carb is upright again and back on the intake manifold if you try this time saver!
PS: do yourself a favor and trim away this foam if it is in contact with your carb!
Hey Cup Cake - thanks for the super quick reply. My description wasn't very good, because I've definitely got an HIF like this: http://www.minimania.com/web/item/FZX1414%2FREB/InvDetail.cfm (without a separate float bowl). I've tried to replace my avatar with a photo, but it got really small...maybe you can still see the squarish bottom without any visible external connecting hose to the moveable choke tube like the HS have. (I also fine tuned my earlier description in the spot where I think I confused things by how I phrased it)
Rereading the earlier posts, it sounds unlikely to be my rubber choke ring since my choke is still behaving itself... So if the float needle valve is usually the culprit then it seems I'll want to pull the carb regardless - there's no chance I'm getting at that bit without taking the carb off the car and flipping it over.
Is there a good "in car" test to rule out the float chamber O-ring or is there an in car way to confirm that the leak is coming from the float needle valve?
From your description I believe you have an HS carb with a separate fuel bowl. An HIF has the fuel bowl intergrated onto the bottom of the carb. Leaks in the fuel bowl are almost always caused by a faulty float needle valve. Sometimes you can get them to seal again by rotating the needle to a new position.
The power of keen observation is often viewed as cynicism by those who don't have it. G.B.S. Sarcasm is the lowest form of wit. Oscar Wild
How can you tell - without pulling the carb out of the car - if your HIF carb leak is due to:
Sticking my head in the driver's footwell the other day to look for water (a completely different problem), I was hit with strong gas fumes. A quick look under the car revealed a 3 inch wide by 2 feet long patch of fuel on the asphalt. A more detailed inspection under the hood turned up a carb that was leaking a drip every second right from the lowest point on the float bowl cap (that "bump" where the INTERNAL fuel tube, THE ONE THAT THE CHOKE LIFTS AND LOWERS, dips ITS right angleD END down into). I could not figure out exactly where the leak was though...
The carburetor was still leaking away after each attempt to stop it. The best theories to date are that there was some siphoning or wicking going on, slipping past the pump and since the float was never getting all the way up, the flow was never being stopped.
So for safety's sake I popped an in-line fuel cut-off valve between the pump and carb (the vise grips were handy for this little job) and am awaiting an O-ring to see if that's the simple fix.
I guess I am posting for two reasons:
Thanks in advance for any thoughts/suggestions/advice!
Sounds like every 38 you've used has suffered from the same poor setup then. I suggest you get someone with familiarity to look them (it) over if you'r lacking confidence because you're right it's not a good idea to have a leaking carb.
Most common failure point on a HIF carb is the little rubber ring in the choke circuit dries up requiring you to run with the choke on all the time. Simple DIY fix with a rebuild kit.
Make sure you don't cap off the vent, and ensure that the float level is set correctly and you've got a new rubber ring in the lid and a new float valve and seat installed (all part of the rebuild kit). If your engine steadies are crap and the engine rocks, the bottom of the float lid will hit the firewall and wear a hole in it from repeated contact, worse of a problem if the car is LHD and the brake/clutch lines are running right there behind the carb. But the problems is still not the carb-- the hole was caused by crap engine steadies/motor mounts.
Have you checked the compression?
I also have a leaking SU on a 1000. I've had the 38's and 44's for years on varioous cars. Every 38 I've had has leaked fuel from the bowl which is a problem with the exhaust header right below it.
Can someone recommend a better carb? Are webbers or others a safer bet? One day I'll perish in a horrible car fire and not have to worry about such things ever again.
Presuming that you have the stock HS carb while you have the dashpot off look at the brass jet assembly that the needle runs in. The center should be around 1/8" or less below the bridge if it is too high it will run lean. To adjust it to richen the mixture you will need to turn the nut underneath clockwise (looking from above) it should be around 12 flats or two full turns out for a decent starting point. Also clean the jet out with some thin wire or similar as it may have the remains of the bad gas in there restricting the flow.
If in doubt, flat out . Colin Mc Rae MBE 1968-2007.
I WOULD LIKE TO THANK YOU FOR ALL OF YOUR CONTINUED ADVICE.
Now, I've taken the carb apart too many times to count. grr.
I'll take it apart once more. I also found online that I could have twisted the spring in the dashpot piston assembly when reassembling it. I'll take that apart once more also. I'll get some Break Kleen and wipe our the assembly, though, to my knowledge(which is limited to say the least), the piston doesn't seem to be sticking, but I guess it could just take the slightest bit of gunk/crud to make it not work.
I have replaced the hoses and clamps around the carb, including fuel lines(installed an inline fuel filter) still the same problem. Car starts when the choke is open, and when I hit the accelerator, it wants to/or does stall. It won't run without the choke being open and even then, the RPMs are high.
Sorry I sound like a broken record.
People often try to fix multiple things at once. Your car failed because the fuel turned to evil goop. Make certain that the carb is the only thing you have messed with.
Remove the dashpot assembly, and the top of the float bowl, remove the fluid from the float bowl and then carefully blow out the jet, this is the connection between the body of the carb and the float bowl. Then, clean the inside of the dashpot and the piston. Use nothing abrasive, just brake kleen and a rag. Note how, when assembled, the piston moves up and down with its action countered by the damper and the oil in the dashpot. The piston moves a certain amount, and it is only necessary to have enough oil in there to dampen its movement.
Check the choke linkage. It should open the throttle slightly as it is first articulated, and then as you pull it further it should drop the jet. This needs to work properly.
Check any and all vacuum lines:  ower brake boosters, and ports that may have been part of removed emissions systems could have leaks. The same evil chemicals that allowed fuel to leach through the plastic of the float bowl cause pretty quick deterioration of many rubber hoses, so you could also have a substantial vacuum leak.
Still, several posts previously it was mentioned that nothing ruins gasoline faster than adding it to old bad gas. 1 gallon of old bad gas + 4 gallons of new gas = 5 gallons of bad gas. This is frequently played out on the racetracks of 24 Hours of LeMons.
Alright, if it's not one thing, it's another
Got the new float installed it, and no fuel overflow...sweet!
Next problem. Now The car won't stay started, and only will if the choke is open at least half way. If not, it stalls right away or as soon as I hit the accelerator. Any suggestions? I do appreciate the help.
Now to get a new one ordered. I sure as heck hope that's the problem. GGGRRR!
There should not be any fuel inside the float.
Thanks for all of the help, sorry my presence here is so limited, no internet at home.
Well, I've had very little time to really tackle the problem, but spent some time the past two weekends. I've added and inline fuel filter (catching lost of debris), put in new fuel hose, pulled the float and float needle, cleaned the valve, but nada. No obstructions that I could see, cleaned the parts put it back together. I was feeling pretty good, went to start the car, and fuel still came out the overflow. Damn it!
I see people mentioning the float being full of gas as a possible problem, and mind you I'm new the the carb, though I'm feeling more confident, but should there be any fluid in the float? If not that is my problem. Had the float out this weekend and there is fluid in it.
Thanks again, Patrick
Found 30 Messages