Help fuel coming out of carb air intake !!

[paolobrags]

:'( Help, I have just purchased a UK RHD Lancia 2.0 litre montecarlo.
When it arrived it ran but was leaking fuel. I traced this to a leaking fuel pump which I have now replaced. Since then fuel fills up and overflows out of the top of the weber carb. I though that maybe that the float was stuck but it is fine apart from that the needle valve that was a little stiff so I have now replaced this but still it throws out fuel. The only thing I thought was maybe the fuel pressure was too how so I have fitted a fuel pressure regulator and even if I turn this right down to 1 psi fuel still comes out. Any ideas people because I really do not know what else to try?

[John O]

Though I'm not sure about the carb on a Monte, it should likely have two fuel lines to it, as does the Scorpion. One is fuel under pressure from the pump, the other is a return line which routes excess fuel (petrol) back to the tank. It sounds to me as if the return line is blocked or in some way non-existent.

John O.

[Will]

:'( Help, I have just purchased a UK RHD Lancia 2.0 litre montecarlo.
When it arrived it ran but was leaking fuel. I traced this to a leaking fuel pump which I have now replaced. Since then fuel fills up and overflows out of the top of the weber carb. I though that maybe that the float was stuck but it is fine apart from that the needle valve that was a little stiff so I have now replaced this but still it throws out fuel. The only thing I thought was maybe the fuel pressure was too how so I have fitted a fuel pressure regulator and even if I turn this right down to 1 psi fuel still comes out. Any ideas people because I really do not know what else to try?

You need to put a mityvac. manometer. or long plastic tube with a very tall stick on the pump and check that you are getting no more than 5lb or so of pressure from the pump if you have not added a regulator, and you have done away with the original metal fuel filter in favor of a modern replacement. The original pump is pressure limited by a magnetically coupled impeller and the original fuel filter contains an ancillary regulator.

Fuel pressure above about six or seven lbs can leak past the needle valves on some webers.

[Darren]

Hi and welcome to the group!

Be good to see some pics of the carb to help - and of the car overall. I agree with John and Will - check that there is both supply and return between tank and carb.

I would also be inclined to carefully take the top off the carb - making sure that you don't bend the floats. You can then check the needle valve and small filter. If the return line is clear and you still have the problem then it could be the floats in the carb don't, or rather one or both of them are punctured, meaning that the fuel supply won't cut off when the chamber is full. All of this pre-supposes that the fuel pressure is correct.

Good luck - overhaul kits are readily available, either on eBay or at The Monte Hospital.

Keep us posted on how you get on!

Cheers

[paolobrags]

Thanks for all your replies. I have already replaced the needle valve and checked the floats so they seem to be working fine. I have also just replaced the gasket between the top and bottom of the carb. I will checked the return fuel hose back to the fuel tank and see if this works. One thing, when I do run the engine the revs are very high and then the cars cuts out. I thought this could just be down to too much fuel going in to the engine.

I have just checked the return hose from the carb to the tank and there is a little fuel coming out so I take it that it is not blocked.

[John O]

I thought this could just be down to too much fuel going in to the engine.

If so, you might want to check to see if you've gotten fuel in your oil.

John O.

[Darren]

Hi again Paolo,

If you still have the same problem after doing that (you did check the floats do floats right?) then there are still 2 issues. 1 too much fuel is present at the carb, and 2 therefore either the return is not working properly or is overwhelmed.

How old are your fuel lines? Do they have any kinks in them? If your fuel supply is at the correct pressure and it's clearly getting to the float chamber, the problem is dealing with the excess. I would try removing the return line entirely and blowing it through, just to make sure. Check the carb end route from chamber to outlet pipe is clear and do the same at the tank end.

Is the float level set correctly? If the fuel pressure is correct and the float level set correctly then technically fuel supply should be cut to the chamber.

Frustrating! Where are you based?

Cheers

[paolobrags]

Thanks Darren I will check those things again. I'm based on the Surrey/South London borders.

The fuel return line from the carb to the tank is not blocked and the floats definately float inside the carb. If I blow through the fuel inlet on the carb I can blow though it and this then shut off if I move the floats up. I have just changed the little fuel filter inside the carb which was pretty dirty and I shall put it back together and see if this makes any difference.

Still no good, not sure what else to try.

[John Allen]

I betting it's the float level. It doesn't take much to bring the level higher than the discharge port in the aux venturi. Make sure you check the actual float dimensions listed in the manuals, just because it 'floats' in the bowl doesn't mean it is at the correct height. Also, make sure you check the float in the 'open' position. Most carbs have a max 'droop' in the float (haven't used a stock carb on a Scorp in a LOOOOONNNNG time so I don't know it off the top of my head). If it is too much, the float can stick in the 'down' (open) position.

I also will bet that it is not the return line. Many cars (FIATs included) do not have a return line and the carbs don't overflow. The reurn line has more to do with vapor lock and emissions than pressure...

-John


Hi again Paolo,

If you still have the same problem after doing that (you did check the floats do floats right?) then there are still 2 issues. 1 too much fuel is present at the carb, and 2 therefore either the return is not working properly or is overwhelmed.

How old are your fuel lines? Do they have any kinks in them? If your fuel supply is at the correct pressure and it's clearly getting to the float chamber, the problem is dealing with the excess. I would try removing the return line entirely and blowing it through, just to make sure. Check the carb end route from chamber to outlet pipe is clear and do the same at the tank end.

Is the float level set correctly? If the fuel pressure is correct and the float level set correctly then technically fuel supply should be cut to the chamber.

Frustrating! Where are you based?

Cheers

[Darren]

Hi Paolo,

I think we're getting closer! I think John may have hit the nail on the head. Check the download section (library) for the tech manual, which may give you the correct setting - the Haynes manual doesn't give it.

I can recommend the Montecarlo Consortium as a worthwhile club to join and there are a few of us who reasonably regularly get together for a beer and a chat - based around the surrey/hants area.

We'll also be at the NEC in November for the Classic & Sportscar show as ever, together with the BetaBoyz, the Lancia Drivers Club and the LMC - definitely recommended to visit for the cars, and if you're they - come say hello!

www.montecarlo.org.uk

Cheers

[paolobrags]

Thanks, I have just ordered some new floats from the MonteCarlo hospital so I will give these a go with the correct adjustments and see how I go from there.

[len_newstrum]

I am a coupe guy, so what I have to say might not be correct for a Scorpion. Probably not, though, since the guts of all DATR-series carbs are identical.

If you go to the Beta forum thread titled, "32 DATRA Rebuilding tips (http://lancisti.net/forum/showthread.php?t=2745)" you will find details on how to set the floats in posts 3, 21, 22, and 23. The factory manual is worthless as it just tells how to use a fancy factory supplied carb test station!

Be sure and check all of the posts as I made a significant boo-boo in post #3. Trying to set the float level the way it is usually done with non-webers (ie, with the floats horizontal) will absolutely give the wrong results. Be sure that the gasket is in place, too.

Do consider going slightly larger on the primary and secondary main jets. The performance increase is definitely worth the very slight decrease in gas mileage.

[paolobrags]

I just thought that I would let you all know that the new floats have cured the problem :cheers:
Thanks for all your help..

You maybe able to now help with the next issue, I think its something to do with the auto choke. The car only likes to start when the air intake on the carb is sealed. If I start the car and then remove this seal the revs shoot up and then the car stalls. I have heard that these auto chokes do give problems and the butterfly thing (sorry don't know the correct term) on the intake does seem to be always open.

Any ideas with this one

[len_newstrum]

Is that the manual choke or automatic choke (with water hoses going to the carb) version? The automatic choke version is USA only, I think; and yes it is tricky.

[len_newstrum]

Is your carb a DATRA (the one with engine cooling water hoses going to the carb)? If so:

Let the car get stone cold, depress the accelerator once. Is the choke butterfly still open? If so, you for sure have a problem.

Before you do anything, scribe the housing that the water goes through and the carb body so that you can put it back precisely right! (That assumes that is right to start with! It is possible that a prior owner or unfamiliar mechanic put it on incorrectly: in which case look for a couple of notches that were put on at the factory and line them up.)

There is a bimetallic coil spring inside that is connected to a three-step cam. There is a spring that moves the choke choke butterfly as the cam moves. When the engine is cold the throttle stop should be resting on the first (highest) part of the cam and the choke butterfly should be closed.

When the engine starts, the intake vacuum acts on a diaphragm to pull (push?) a rod that rotates the cam a little bit so that the engine runs at fast-idle. As the water gets hotter, the cam rotates some more until it is finally at normal idle with the choke butterfly all the way open. You have to 'blip' the throttle a bit to take the drag of the throttle adjusting screw off of the cam so that the cam can move.

It sounds to me like maybe the diaphragm might have a leak, the mechanism might be binding, or the spring between the cam and choke butterfly might be broken or come off.

Make sure that the bimetallic spring is hooked up right when you put it back together. Spraying a little light oil into the cam area would be advisable.

If the choke butterfly is closed when the engine is cold and moves in steps to open as the engine heats up you shouldn't be getting the symptoms that you describe. In that case I would suspect low-speed/choke fuel circuit. How is the idle? Have you diddled with the idle mixture screw? When setting up the carb you have to start with it out only two turns, then adjust very slowly in/out until it starts to run rough, the put it somewhere in between, then readjust the idle. If it is less than one turn out, or more than four turns out something is wrong (like the gap between the throttle plate and the carb throat). Let's hope that isn't the problem because you have to take the carb off and use a wire feeler gauge to set it correctly.

The Webers are unique in that the idle circuit is not independent as it is in most carbs. If the idle mixture is way off it screws up the whole low-speed circuit, which affects low speed performance. Are the low-speed primary main jet and air-corrector correct and clean?

Len

[Darren]

Is that the manual choke or automatic choke (with water hoses going to the carb) version? The automatic choke version is USA only, I think; and yes it is tricky.

Hi Len, no the water temp autochoke is not particular to the USA. My Beta had it (2 litre) and all of the Monte's have them too. You are right that they can be tricky to set up though. You need to make sure that the end of the strip does locate in the prong in the water pipe side of the assembly. Check the action to make sure it's all free and working properly as mentioned in other posts - and check to see if the butterfly does close on the second choke.

I'm not sure what would cause the revs to rise without the airbox connected - badly setup mixture/timing/carb? I'd maybe get it to a garage to have it tuned if you don't have the equipment to set it up properly?

HTH

[paolobrags]

Thanks again guys for your advice, it is much appreciated. I just took the housing off the side of the choke and the little pin that sticks out from the side of the carb was lose so therefore the butterfly is just open. If I move the throttle out of the housing and move the pin up the butterfly closes. But as soon as I move the throttle again the pin and butterfly are lose again. I can see in the housing of the choke that there is a metal coil, I take it that somehow that pin hooks under this coil but I'm not 100% sure where abouts it should hook on.

I have fixed the choke, there is still too much air getting into the carb, if I cover the air intake on the carb the car runs, if I then take it away the car stall. I take it there must be an idle screw on the carb, would this cure the problem if I adjust it?

I have found the idle screw,take its the one one the side of the carb. If I screw it all the way in the cars starts splutters and then stall. In have tried gradually turning the screw bit by bit but the car will then not start at all again unless I completley cover the air intake. What else could be causing too much air getting in?

[len_newstrum]

I have fixed the choke, there is still too much air getting into the carb, if I cover the air intake on the carb the car runs, if I then take it away the car stall. I take it there must be an idle screw on the carb, would this cure the problem if I adjust it?

I have found the idle screw,take its the one one the side of the carb. If I screw it all the way in the cars starts splutters and then stall. In have tried gradually turning the screw bit by bit but the car will then not start at all again unless I completley cover the air intake. What else could be causing too much air getting in?When you say that you cover the carb intake, do you mean that you are covering both the primary and secondary, or just the primary? If you are covering both you could be forcing the engine to run on just the secondary. Have you tried just one, then the other?

I don't think it a matter of "too much air getting in" but 'too little fuel getting in'. Putting you hand over the intake pulls more fuel through, but when you take it off the engine runs very lean and speeds up until it simply doesn't have enough fuel coming through to keep on running.

It really sounds like the primary low-speed circuit is clogged, which means as a minimum removing the primary main jet, air corrector jet, and idle screw entirely and using compressed air to blow the circuit out. Start with blowing into the idle screw opening, otherwise you may just be pushing the clog in tighter! Check the jet sizes while you have them out. Be careful when putting the idles screw back in, if you tighten it too much you can wreck the seat--finger tight does it. Set the idle screw at 2 turns out.

If that doesn't do it, it is time to disassemble the carb and soak it in carburettor cleaner.

[paolobrags]

The cars runs better when I just cover one of the intakes, the one with the butterfly in it for the choke. I have already tried taking all the screws out and cleaning them and then blowing through them to make sure they are not blocked and they seem fine but they could be blocked inside the carb itself. One thing, when the ignition is on without starting the car I can hear excess fuel being pumped back into the tank.

[len_newstrum]

The cars runs better when I just cover one of the intakes, the one with the butterfly in it for the choke. I have already tried taking all the screws out and cleaning them and then blowing through them to make sure they are not blocked and they seem fine but they could be blocked inside the carb itself. One thing, when the ignition is on without starting the car I can hear excess fuel being pumped back into the tank.That sounds to me like crap in the low-speed fuel passages or jets.

Remember that I'm a North American Coupe guy, so what I say might not apply to your car! US Lancias are wired in such a way that the fuel pump won't come on until you actually spin the engine over and the oil pressure comes up from zero. I think the objective is safety: if you get into an accident and the fuel lines in the engine compartment are broken, but your battery is still working, the electrically driven pump shuts off so you don't continue continue to pump gas all over the place. I've hear it said that it also makes sure that the crankshaft is well oiled before any loads hit it, but I don't think that is a valid arguement. If your car doesn't have that feature--or somebody has rewired it--hearing excess fuel dumped back into the tank would be normal. BTW, I added a push-button on my dash so that I can fill the float bowl before starting the car if it has not been running for a while. If it sits for a while, the fuel in the carburetor evaporates and the fuel in the line drains back into the tank, so you have to grind away with the starter for quite a while until the float bowl fills up again. About 10 seconds on the button and instant start! I just replaced the cigarette lighter with a button; looks like it came that way. Lancia put out a service bulletin to put a check valve in the gas line near the carb in order to solve the problem; but it only solved the drain-back problem, not the evaporation problem (assuming that you think overusing your starter is a "problem").

[paolobrags]

Thanks Len, on this car the fuel pump runs as soon as you turn on the ignition but from what you have said I can see why the US ones had the other feature. I have just bought some carb spray so I am going to take out the needles in the centre of the top of the carb out and spray inside the housings. I have already checked the needles themselves and they are not blocked. As you mentioned in the last reply this is a fuel problem as if I pour petrol into the top of the carb the car runs but as soon as I stop the car stalls. I have checked the needle valve and fuel is coming into the chambers where the float is so it can now only be something small that is preventing the fuel to be released into the inlet manifold.
I have also fitted a fuel pressure regulator and even if I turn this up to 5 psi it makes no difference as I have already found out that these carbs like to run at 3.5 psi.
Apart from the needles on the top of the carb and the idle screw is there any other ones that I should try and clean?

Good news, after cleaning and spraying every known needle, hole etc I can get the car running, well just about. I have to keep the throttle half open, anything less and the car splutters,stalls and pop smoke out of the top of the carb. Even when it is running the engine is quite lumpy. Any idea's?

[John Allen]

US cars also had an idle cut-off solenoid on the side of the carb. Not sure if other countries had it, but it's worth a check. I've seen the wire come off of this (or not installed after and engine swap) and the car will not run.

It is a cylindrical attachment on the side of the car with a (red?) wire coming out of the middle of it. The solenoid gets power when ignition is on and pulls a valve open to allow fuel to the idle circuit. If you have it, and it is suspected to be bad, unscrew the solenoid and pull out the tapered plunger - it will work fine without it.

[paolobrags]

US cars also had an idle cut-off solenoid on the side of the carb. Not sure if other countries had it, but it's worth a check. I've seen the wire come off of this (or not installed after and engine swap) and the car will not run.

It is a cylindrical attachment on the side of the car with a (red?) wire coming out of the middle of it. The solenoid gets power when ignition is on and pulls a valve open to allow fuel to the idle circuit. If you have it, and it is suspected to be bad, unscrew the solenoid and pull out the tapered plunger - it will work fine without it.

John,

It does have this solenoid with a red wire coming out. I will check the solenoid.

Thanks