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Greetings,

We have a continuing problem with a leaking carb.  It has twice emptied the fuel in the gas tank while sitting parked in the driveway; a third only a little because it was caught early.  Gallons of fuel.  Drips out of the carb and down onto the engine and exhaust below.  Fuel also leaks into a cylinder.  A fast, fast drip.

Note, that between these episodes, that happen every 3-6 months, the car runs absolutely beautifully.  No backfiring or popping either accelerating or deaccelerating.  My only issue has been a very large smell of raw gas at times and a low MPG of around 17.  I thought I'd fixed this when I replaced the gas cap with the correct cap.  This on a 1600 cc motor.

I have the smaller EPI carbs on the car.  We think they are Chinese.

This leak out has happened three times when parked nose up on a slight incline with everything turned off including the main electrical shutoff.  The electrical system is off.  No pump running.

We switched the right leaking carb to left side and it didn't leak.  But that's not telling as the car mostly works (doesn't leak) except when it leaks out.  We have rebuilt both carbs with carb rebuild kits and assured that the fuel pressure is less than 2.5 psi.  Checked manifolds for leaks.  As typical, the car runs very well now.   I could likely start driving her again but I just don't trust her.

We have just ordered two new floats hoping they may be the issue and will replace when they arrive.

Can anyone think of something we've missed?

Marshall

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Solex/Kadron carbs need 1.5 psi. Not one smidgeon more(2.5 psi is too much). That's probably your issue.

Drop the fuel pressure and replace the float valves(they are not expensive even with a full rebuild kit). If the floats are leaking, i.e. they don't float, replace. Otherwise, if they float and there is no gas inside(shake them) they're fine.

Electric pump, add auxiliary regulator. Mechanical pump, add gaskets under the pump until running pressure is correct.

FYI, this is what works from my personal experience, as in I have done this myself. This is not anecdotal internet BS.

Last edited by DannyP

The FCR carburetors on my Ducati leaked twice, both times it was because E10 had eaten away the rubber tips (seals) in the float bowl needles. Luckily, motorcycles have petcocks so I noticed it as soon as I opened them up. Haven’t had a problem since I began using ethanol-free gas.

Although if you’ve rebuilt the carbs those needles would have been replaced?? (I have no idea. I’ve never laid hands on anything but SU’s and Dellortos)

.

Everything Danny said... except...

Even with leaking needle valves, I can't see a whole tank of gas flowing out of the carbs. I'd think after you'd lost maybe a quart of gas, pressure in the line would be very low with the engine (and fuel pump) stopped. My needle valves were worn out (Weber 40 IDF's) and I'd get a strong smell of gas around the carbs about 20 minutes after parking the car. But that would dissipate after a few hours, and never enough gas to see an actual drip.

You say this happened parked with the nose up. I guess if the nose were high enough above the carbs and the needle valves were bad, you might end up siphoning all the gas out of the tank, but I've never heard of such a thing happening - ever.

Did this happen in very hot weather? I'm thinking maybe your tank has no vent line (or the vent is plugged) and pressure is building up in the tank as the sun works its magic on a parked car.

Do replace the needle valves (and check the old ones you take out of the carbs for wear), but I think I'd look at the tank vent line, too.

.

These carbs MAY be jetted a little rich, but the real reason for crappy mileage is TOO MUCH FUEL PRESSURE.

I agree with Mitch, once vapor pressure is relieved the gas should stop flowing. How much of an incline is it? It could just be a simple siphoning action. Siphons work pretty well once started.

Your fuel pressure is too high, and your float valves need to be replaced. You may also need to vent the tank. Do those three things. All three.

I'll say it one more time for it to sink in. 1.5 PSI, no more for EMPI/Solex/Kadron carbs.

Last edited by DannyP

Thanks to all for your input.  Ordered the float valve replacements and needle valves.  I'd misspoken regarding fuel pressure.  We have an electric pump and a regulator and that was always set low around 1.5 psi.  The tank is vented but will check again.

Will post once EVERY part is replaced, adjusted and tested over several months to see if this issue is finally solved.

Thanks again,

Marshall

Is the regulator set to 1.5 psi? Because without physically putting a fuel pressure gauge on the line you don't really know the pressure.

The 1.5 mark on the regulator could be quarks or parsecs or something. Just because it says 1.5 doesn't mean that's the actual pressure.

I know I've said this before but it seems to always fall on deaf ears.

Last edited by DannyP

Proper fuel tank venting is important, even if the floats and needle valves are perfect. If there is a one way valve in the vent line (lets air in as fuel is used, will not let air/vapor out)  you can build up pressure in the tank if fuel volume is low, ambient air is cold while turned off, and then ambient air (and the tank) get hotter before a restart. the hotter vapor in tank tries to expand, can't, pressure builds, enough to defeat the float/needle valve. gas floods carb and goes wherever. can fill the crankcase, and that is an interesting experience if you fire it up and try to drive it.  Ask me how I know.

Marshall

I believe you are on the right track.  The float valves or something in that fuel delivery circuit (dirt, rubber bits) that inhibits float valve operation is going to be your problem.

When the car is parked (ignition off), the only thing preventing fuel from from flowing into the carb (and beyond) is the float valve.  If the float valve is defective or obstructed, then over time fuel can flow into and through the carb until the gas tank empties; just the same as if it were sitting there idling (for 3-6 months).

I've seen this happen.  I don't think it was that uncommon, maybe isolated to the Chinese carbs.  I know Kirk would send out a new carb just for the sake of a phone call.  Personally, I have removed the air filter and have seen the carb full of gas, overflowing the top and onto the floor.  Obviously fuel had already filled the manifold, cylinders, sump, etc.

Be sure to back-flush the fuel inlet port and jet with compressed air or carb spray before installing the new valve.  Any fleck of dirt or rubber bits ('ethanol induced') that can wedge between the needle and seat will continue the same problem you are having.  The fuel inlet circuit above the valve must be clean.  When you blow it out, do it over a white rag to see if anything comes out.  If you find black rubber bits, then you'll need to look upstream and replace whatever is deteriorating.

And:  Before firing up, change the oil and rotate the engine a number of revolutions without spark plugs installed.  You don't want gas in the crankcase oil, or try a compression stroke on a cylinder full of gas.

And:  When you get the car home, disconnect the fuel line from the carb until you do your repairs.  If you find that it drip, drip, drips when disconnected, then you know that drip, drip, drip can flow straight through a defective float valve.

Last edited by RS-60 mark
@RS-60 mark posted:


Be sure to back-flush the fuel inlet port and jet with compressed air or carb spray before installing the new valve.  Any fleck of dirt or rubber bits ('ethanol induced') that can wedge between the needle and seat will continue the same problem you are having.  The fuel inlet circuit above the valve must be clean.  When you blow it out, do it over a white rag to see if anything comes out.  If you find black rubber bits, then you'll need to look upstream and replace whatever is deteriorating.



Don't use any more than about 10-15 psi if you use compressed air. A little carb spray should be sufficient.

I've found that Solex/Kadrons will run for YEARS without clogging up. They are trouble-free compared to Webers or Dells. The idle jets are certainly not any bigger or smaller, the design of the carbs just doesn't promote troubles. Musbjim knows...

On my recent engine build I noticed something interesting. You know those big washers with a thin black rubber washer that go on top of the CB air cleaner tops? When new, little tiny pieces of rubber come off and fall through the stud holes RIGHT ON TOP of the carb every time they are removed or installed. Where do you think they end up? Right in the idle circuit air intake. After a while, the rubber gets worn enough that rubber stops chunking off.

Last edited by DannyP
@DannyP posted:


On my recent engine build I noticed something interesting. You know those big washers with a thin black rubber washer that go on top of the CB air cleaner tops? When new, little tiny pieces of rubber come off and fall through the stud holes RIGHT ON TOP of the carb every time they are removed or installed. Where do you think they end up? Right in the idle circuit air intake. After a while, the rubber gets worn enough that rubber stops chunking off.

I noticed this too, so I used an exacto blade and removed the rubber that touches the threads. I also cleaned the threads while holding the shop vac hose to catch the crud. I guess one could also use a drill bit or a small round file to remove the excess rubber.

Last edited by Carlos G

I borrowed back the car to take advantage of this and next week's spectacular weather here in the DC area.  Those new needle valves and floats are arriving late next week.  Until then I'm driving!

An apology.  I think I misspoke re the brand/type of carbs on the car.  They are dual EMPI 34s.  Does this change the recommended pressures everyone is talking about?

I drove the car yesterday.  Some symptoms.  After warming up, it would stall when approaching or sitting at lights or stop signs - unless I actively revved the motor.  The idle was much less than 1000.  No faultering when I accellerated.  Car started quickly after a stall.

Remember, both carbs have been rebuilt with kits, cleaned, etc.  Only the floats need replacing.

After returning home after that drive, I checked the regulator and changed from over 3 to a little less than 2.  Adjusted both idle screws to raise warm running motor to around 1000 rpms.  Took another ride.  Car backfires softly on deacceleration.  Not badly but something new.  Also, when I accelerate there is a distinct faltering feel when shifting up through the gears -- particularly between 2 and 3.  If I floor it, there is that delay for a second or two.

I raised my fuel regulator this morning to 2.5 psi and will try the car again soon. 

Marshall

I don't understand why you think you can get it running well when you have a known carburetor float valve problem that isn't fixed. If the float valves are leaking there won't be a stable fuel flow no matter what screw is turned.  Also, at the risk of sounding snarky, don't post pics if it burns to the ground while being driven with a major carb issue. Those are pictures I really don't want to see. Please be careful and maybe wait to drive until after the leak is fixed. There'll be other nice weather days ahead and driving pictures from those we all want to see.

I decided not to heed the advice about not driving. At midnight last night out across Chain Bridge (the fall-line of the Potomac River, up Arizona Ave, to MacArthur Boulevard (following the path of the Delcarlia aqua duct) all the way to Old Anglers Inn on River Road, back to the Clara Barton Parkway (zipping past murky deer feeding in the median) down River Road that parallels the C&O Canal, through Georgetown back across the river on Key Bridge and via GW Parkway home — some 20 miles under the remnants of the Harvest Moon on a glorious 55° evening. Magical

photos of carbs forthcoming.

An update.

We have totally rebuilt both carbs.  Have changed out every gasket, every float, every washer, every everything.  Everything is set correctly.  The issue.  When we turn on the ignition switch and the fuel pump starts to "click" and we look into the open carb, SOMETIMES, there is a constant flow of gas out of the main jet.  There does not appear to be any consistency to this.  If we turn the switch off and back on the stream may or may not occur.  But it's happening constantly now with the right carb but not the left.  FYI, the left carb was on the right before we moved it over.  In its previous place it had also leaked out several gallons of gas.   

Because of the ongoing leak, we have subsequently removed, recleaned/blown out and reinspected the right carb 3 more times.  We have tested the fuel pressure.  Have set and tried 2, 2.5 and 3 psi.  The floats are 8MM.  The sporatic and incomprehensible leaking problem on the right carb persists.

We have given up and ordered a pair of Spanish-made Webers. 

Because the carbs on your car are NOT Webers, they are Solex. As such, they require 1.5 psi, no more. More than 1.5 psi WILL damage and overwhelm the fragile float valves. All this was previously stated by Alan and myself.

Apparently, you just don't get it. You ask for help, get answers, then don't follow the (wise) advice. That is the definition of something, all right.

I'm out.

Dannyp.  I am not ignoring you or your advice.

We are under the belief that what we have are dual EMPI 34 ICTs.  We believe that these are Chinese Weber knockoffs and not Solexes.  I've reread the installation page that Allen gave me and it doesn't refer to the type of carb make they knocked off or any reference to pressure psi (which might give us a useful clue.) 

Can anyone tell me definitively from the photos I enclosed earlier whether this is a Weber or Solex?  Do these two carbs look remarkably the same?  FWIW, I will say that the needle valve was metal to metal - no rubber.  My mechanic is adamant that this is Weber.  The rebuild kit was for a Weber.

We've ordered a Spanish made Weber replacement.  At least then we'll know what brand we have.  We are at our wits end with the inconsistent and dramatic flow of fuel into the right carb after the engine is turned off - sometimes.  We've had to change the plugs twice in as many days as they carbon up.  If started the engine quickly starts to run on only 2 cylinders.

We think that the best solution is to start with new carbs. 

Thanks,

Marshall

You have EMPI 47 - 7411 duel 34mm Carbs , ( Look at your second photo and above the screw on the right side of the carb, it is stamped EMPI )  When gone through and set up correctly these carbs are decent on a mid cc engine as you have . However, they need a fuel pressure of no more than......... 1.5 lbs .....to function correctly. When I buy these carbs the first thing I do as I did with yours, is to disassemble each carb, check for manufacturing debris and confirm nothing is blocking passages etc. Then set the floats (they are never correct from the Mfg. ) Lastly I pre-set the butterfly so that both carbs have the exact base line sync ,  I then run both carb's idle screws in exactly 2 turns which still keeps the carbs mechanically synced. This is a start up point that allows the engine to run while making additional mixture and idle speed adjustments.  Constantly changing out two fouled plugs then restarting you engine will quickly "gas wash" the two cylinder walls that are getting unrestricted gas flow and dilute your crank case oil which will destroy the, rings, guides,  main and rod bearings hence, you may soon be looking at a full engine rebuild.  ( Check compression now see John Muir's book for the correct procedure) ) As mentioned, all you need to do is add in a quality in line fuel pressure regulator and set the fuel pressure up with a quality and accurate  fuel pressure gauge. I am 90%  sure that your  " gas leak "  when the car is parked with the engine facing down hill from the fuel tank is a carb needle to seat issue ( excessive fuel pressure) which is allowing unrestricted fuel flow. This is "basic mechanic's 101" aka lawn mower knowledge, perhaps you may want to consider locating another mechanic.              Hope this information guides you .

This is your duel carb kit:

https://www.amazon.com/Empi-47...633464997&sr=8-3

Last edited by Alan Merklin

That’s the gauge. It also has a small dial.  We have a pressure/vacuum meter to measure system accuracy.

I’m at a huge disadvantage here as the car is an hour away and I’m not doing the work on it (not that I could.). I’ve passed on everyone’s useful info.

We have pulled the carbs 4x. We have collected all the brand and model info from them (of course), talked to EMPI, installed a rebuilt kit, assured the electric fuel pump is the 1-3 psi model and not the 3-6 one, carried out the breakdown, cleaning and reassembly setup steps that all of us know all too well, changed the oil (to be careful) and still the problem persists.

We are punting and have purchased a new carb set.

Thanks to all for your advice and council.
Marshall

et al.,

We replaced the carbs with a new set of Spanish-made Webers.    The carbs were fully set up as we all know they must be.  We used the re-jetting and float setup recommendations of https://www.wayoutwestie.com/m...he-whole-of-england/

We left the faulty fuel pressure gauge and fuel regulator on but set the fuel pressure independently with an accurate pressure gauge.  Those parts will be replaced next.  The carbs are running beautifully.

I was going to sell the old EMPI carbs on Craig's List or Ebay but they are junk.  It's a miracle that I didn't burn up the car in trying to get to the bottom of the issue.

Thanks to everyone who provided useful help on this.

Marshall

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