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Dumb-ass carburettor Q?


danthecapriman

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The Mercury went out the other day to the Pompey meet up. Started up fine at home, drove to the petrol station down the road and filled up. Started up fine afterwards and drove to the meet up, again faultless.

 

The only thing it did which brought back bad memories from it’s flooding issues last year was a slight petroly odour about half way there which then went away.

At the end of the day though I started it to drive home (sat switched off for a good 5 hours or so all day) it wasn’t so easy to start but caught and idled. It then started idling progressively worse and cut out (familiar story with this sodding car!).

Restarted which was a pig, lots of cranking and foot to the floor on the gas, and it started. To me that’s exactly what it was doing last year when it kept flooding itself.

 

Driving it home was difficult as it tried to cut out every time you come up to a set of lights or give way lines unless you can keep a bit of gas on...

basically I’m convinced it’s flooding itself again.

 

This afternoon I fired it up to see what was going on with it.

It started first try no problems after sitting overnight. Idles great.

This is where I noticed something...

 

On my car the pump is mechanical and sits on the side of the engine, carb is up in V, in the fuel hose between them has an in-line filter, the usual clear plastic disposable ones. The filter sits horizontal more or less along the base of the carb, pretty much level.

When first started and it’s running fine the fuel comes through from the pump and fills the filter roughly halfway up, roughly level with the inlet and outlet tubes.

Once it’s been running a while it starts to get a bit lumpy and the filter then starts filling up more and more.

Just now, I’d left it running long enough that the filter had completely filled to the brim. There was no free space inside it except a tiny air bubble at one end.

 

 

Now the question.

 

That’s not right is it?

On my other carb cars the filter (same type) only ever seem to fill about half way up. Never full.

I don’t think it should fill all the way like it is on the Mercury like that. Surely that sounds to me like for some reason too much petrol is being pumped in and the engine can’t use it quick enough. Eventually it pumps the filter full, when that runs out of space to fill it keeps pumping it into the carb float bowl instead. Eventually they fill up too much and the only thing left is to flood the engine.

 

Any ideas? Or are the filters normally meant to fill to full?

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I would suspect the cause of your problem to be the needle valve in the carb. The fuel pump will always pump a little more fuel than the engine can use. Otherwise, the engine could be starved of fuel at high loads and revs. In practice, the fuel needle will fill the float chamber and cut off the incoming fuel. It will open and close many times.

 

So I would check that the fuel needle actually opens, closes, and seals properly and is not sticking for any reason. Also check for a leaky fuel pump, check for any signs around the pump that suggest it may have been leaking.

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I would suspect the cause of your problem to be the needle valve in the carb. The fuel pump will always pump a little more fuel than the engine can use. Otherwise, the engine could be starved of fuel at high loads and revs. In practice, the fuel needle will fill the float chamber and cut off the incoming fuel. It will open and close many times.

 

So I would check that the fuel needle actually opens, closes, and seals properly and is not sticking for any reason. Also check for a leaky fuel pump, check for any signs around the pump that suggest it may have been leaking.

It did this last year, it was worse last year though.

The carb was full of mank last time. All from a silted up tank. The tank was replaced for new, lines cleaned out and new pump fitted. No leaks on any. The carb was cleaned out and it ran fine after that until now.

In theory there can’t be any shit left in the system as it’s all been cleaned out or replaced.

There’s got to be something up with the carb, though.

 

It’s getting incredibly frustrating now!!

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Does it have a return fuel pipe (returns excessive fuel to the tank)

If so was this blown thru when the new tank was fitted or just taken as ok?

Also did you change the tea-bag (filter)on the fuel take up (in the tank) or was the old float and gear used?

If it comes to the crunch you can always use a MOGGY MINOR electric fuel pump I had one on a 1970 V8 Ranchero never had any starvation problems as there's not much fuel pressure.

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When you started it up yesterday afternoon it was black smoking like a bastard. I'd guess at sticky needle valve in the carb or a sunk/sticky float for a starting point, especially as it has stood for a short while without a good run.

Auto choke on this? Is it working properly?

Wouldn't worry about the fuel filter. I've had various cars with various levels of fuel in them they all ran okay.

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A good point was made there about Ethanol in the fuel, it tends to attack (rubber) seals and can cause many otherwise "pulling my hair out" problems. Did I read somewhere that Ethanol content in petrol has been 15% for some years now?  Also, it comes into my thoughts that you may have a punctured float, which will cause flooding.

 

As has been said, if it has an auto choke, visually check it actually works as it should.

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Cheers guys.

 

The tank, all seals etc have been changed. All sender, sock filter etc were cleaned up, tested and reused. Should be no issues there.

Return pipe. There’s one metal pipe into the pump and one out to carb, I don’t think there’s a return on this. But I’ll double check. The lines were all checked and cleaned when the engine got rebuilt and they’ve been blown through last time the carb played up.

 

When you started it up yesterday afternoon it was black smoking like a bastard. I'd guess at sticky needle valve in the carb or a sunk/sticky float for a starting point, especially as it has stood for a short while without a good run.

Auto choke on this? Is it working properly?

Wouldn't worry about the fuel filter. I've had various cars with various levels of fuel in them they all ran okay.

Yes, it did fire up but wasn’t as good at starting as it usually is. I noticed it was smoking and Eddy said the same. It stumbled and cut out shortly later then really didn’t want to restart. To make it start I floored the gas and cranked it which eventually got it to catch. Obviously that’s not how it’s meant to start and that seems constant to over fuelling to me?

 

Ethanol, I usually use super unleaded in this as the ethanol content is lower. If it gets normal I use an ethanol stabiliser additive. However, the last time it played up like this the carb had quite a bit of nasty brownish mank floating around inside along with some of the old shit and rust flakes in the bottom from the old rotten tank. Could the brownish mank be ethanol that’s started going off? I can imagine that stuff sludging up needles and jets?

 

Whatever the hells causing this I think it’s definitely the carb at fault then (not the pump over pumping?). I’ll need to take the top off the carb and see wtf is going on inside.

I did think it a bit odd that the filter was filling right up like it was but maybe that’s just how this car is?

 

I’ve still got my reservations about this carb too, it’s an Edelbrock replacement that was shoved on (badly!) over in the US to get it running again. When it came here it had the base spacer plate and a few other things missing (now rectified) but I just wonder if this carb was some old turd laying around from something else they just shoved on to get my car running again. Maybe it’s a bad carb? I’m very very tempted to rip it off, smash it to bits, and buy a brand spanking new one and just start from scratch myself?

 

 

Edit; the choke is an auto electrically operated choke. It does seem to work as I took the air filter lid off today and started it. It does open up as it should.

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Cheers guys.

Yes, it did fire up but wasn’t as good at starting as it usually is. I noticed it was smoking and Eddy said the same. It stumbled and cut out shortly later then really didn’t want to restart. To make it start I floored the gas and cranked it which eventually got it to catch. Obviously that’s not how it’s meant to start and that seems constant to over fuelling to me?

 

Yup, that's the clue I'd work with first. Reasons for over fuelling being stuck needle valves in the float chambers, autochoke stuck on (don't know how it works on this car but I'd assume some sort of bi-metal, water heated coil thingy) or a float sinking (they do that sometimes without rhyme or reason). Eliminate those and work from there.

Standing never does any mechanical object any good so I'd safely say that a bit of fettling and a good run and all will be fine!

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Rip it off ,smash it up  ..Buy a brand new one ,and post lots of pics  :-D  :-D

Of the new carb or the smashing of the old one!?!

 

 

I’ve got a wedding to do in this old swine of a car in exactly one month. Nothing like a deadline to put pressure on! And it’ll be embarrassing if it fucks up on the big day.

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This sounds oh-so-familiar. it wasn't that long ago I read your epic thread on this car.

 

I have to agree with the comments here.. this definitely sounds like over-fuelling, and the first likely culpret of that is the float valve. First thing to do is dismantle and clean, and identify if there is any sludge or crap evident. You should also look for anything mechanically snagging in the float area. If the float catches on anything and is prevented from lifting up to close the valve off, then it will flood.

 

Does this have a fuel return? If not, this may be part of your issues. A flow-only setup needs to run at very low pressure and use a fuel pump that can be very-nearly stalled without it building up lots of outlet pressure, or that pressure will simply blow fuel past the float valve and flood the carb. The use of a fuel return means that you can use just about any fuel pump you fancy, as even at minimum-fuel-useage (idle) the fuel delivery to the float valve is at a very similar (if not identical) pressure to when at WOT and hence using *quite a lot* of fuel.

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I don’t think it’s got a return line.

The pumps aren’t anything special though, just a normal mechanical jobbie, not too dissimilar to the ones on my old Fords, just a bit bigger. It’s a standard replacement part so ‘shouldn’t’ over pressurise.

I don’t know if the original carb set ups had a return line though? It’s all gone now so I’ve got no idea what was there to begin with and if this new carb is actually wrong or set up and installed wrong.

 

The more I think about it the more I’m thinking it’s this specific carb causing this. Maybe a brand new one and start from scratch is the better answer? Even the same carb just new and a complete kit?

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I've had fun with carbs needing repeated cleaning, I think it's modern petrol dissolving ancient fuel residues from tank and lines so it can pass filters and then turn into shitty green gook in the float bowls, it's very trying. I worked in a place years ago that did a lot of yanks, they loved sticking on replacement carbs, often misdiagnosed, it should be law to check plugs, leads, the whole ignition caboodle is top notch before poking at a carby.

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This sounds like flooding. You won’t notice it so much at higher throttle or revs, but it will be bad at idle and low throttle. It is either:

-needle valve not shutting off

-leaky float

-float height set too high

That’s exactly how it is. At the moment it seems to be intermittent wether it does it or not but leaving the meet up the other evening, it was ok all morning on the way there. The way back it was a bastard to start and did not want to idle, just keep choking itself out. The only way it’d run was with the throttle on.

 

It’s almost like it’s fine for a while, then the internals start gumming up and something sticks causing the flooding. It was pretty hot that day and the engine was warm having been used in the morning so perhaps that’s not helping things either.

 

7 and12 please.

Seriously, did you replace all the rubber pipes? I wonder if maybe they are degrading and causing the issues? A carb strip beckons....

All rubber hoses are new, ethanol compliant hoses.

 

I think the best thing to do here is just buy a full carb rebuild kit, gaskets, jets, needles and floats and clean it all out. Fit the new bits and set it up then try it?

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I don't know the exact mechanics of how its supposed to work but I have heard of people dealing with fuel over pressurization where there is no return to the tank, by fitting a return loop - it just needs to go to an unpressurized part of the system - ie pre-pump rather - not necessarily back to the tank.  You can get inline filters with extra take-offs for this purpose

 

My Mk2 Granada has an inline filter in the engine bay which always runs pretty much full.  I don't have any running issues now, it can be slightly harder to start when hot but nothing that I consider 'out of spec'.  However I did spend the first 18 months of ownership chasing what I would have sworn was a fuelling problem that actually turned out to be closed up valve clearances. 

 

The symptoms were slightly different to yours, poor idle all the time, smell of petrol, loss of power, very poor fuel economy.  Its night and day since I reset them.  I suspect mine was caused by valve seat regression despite the previous owner claiming it has been converted for unleaded, but yank tanks may not have this issue since they were on unleaded many years before us.

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I don't know the exact mechanics of how its supposed to work but I have heard of people dealing with fuel over pressurization where there is no return to the tank, by fitting a return loop - it just needs to go to an unpressurized part of the system - ie pre-pump rather - not necessarily back to the tank.  You can get inline filters with extra take-offs for this purpose

 

My Mk2 Granada has an inline filter in the engine bay which always runs pretty much full.  I don't have any running issues now, it can be slightly harder to start when hot but nothing that I consider 'out of spec'.  However I did spend the first 18 months of ownership chasing what I would have sworn was a fuelling problem that actually turned out to be closed up valve clearances. 

 

The symptoms were slightly different to yours, poor idle all the time, smell of petrol, loss of power, very poor fuel economy.  Its night and day since I reset them.  I suspect mine was caused by valve seat regression despite the previous owner claiming it has been converted for unleaded, but yank tanks may not have this issue since they were on unleaded many years before us.

Yeah I’ve heard of fitting ‘loops’ too, never seen it or done it though...

In theory it makes sense as it’ll just direct some of the petrol back around.

70’s yanks should easily cope with unleaded, as you say they used it back then, way before we changed over. My engines been fully rebuilt at any rate so wear won’t be an issue, it’s not done much mileage either so things should all be good in that respect.

It’s annoying really as it’s a sweet runner and the idle is good too when it’s not playing up.

 

 

 

 

I’ve just ordered the bits to get this sorted (hopefully!). All direct from the carb manufacturer, should be here Tuesday. I’ve ordered:

Pair new floats and float hinges.

Tuning kit (contains new jets, assorted springs etc etc)

Full complete rebuild kit (full set gaskets, fittings, needles & seats etc etc)

 

Basically everything that I should need to get rid of this problem! That lot weighed in at just under £130.

Out of interest a new 1406 performer carburettor costs just under £400 direct from Edelbrock EU so it’s a fair saving over my ‘fuck it, replace the lot’ approach!!

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Mechanical fuel pumps of the diaphragm sort (which I assume this is) only pump when they need to, the pressure in the fuel line to the carb is actually produced by a spring so it is very unlikely to be over-pressuring. 

 

As suggested above, float valve, punctured float or float height.

I have experienced the entire float valve coming loose (BMW / Zenith 2B2 carb) and a worn out float valve needle (Solex thing on PRV6 Renault) that gave exactly these symptoms. (And massive fuel consumption)

 

Dismantle the carb and clean and check everything as a first step.

 

I don't trust those plastic in-line fuel filters. I doubt it is the problem you describe here but those filters have caused me a lot of trouble on cars, and the one on the lawn mower is annoying me now. Without looking at all dirty, they seem able to block the flow of fuel completely somehow. Maybe if they get a wee bit of water in them or they completely dry out? Don't know, but anyway, replace regularly and always carry a spare.

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Dismantle the carb and clean and check everything as a first step.

I would whack an overhaul kit in it on a general principle, including new needle and seat, float and everything.

Note: These kits come in several stages, always buy the master kit that contains everything.

The float often must be bought separately.

 

I don't trust those plastic in-line fuel filters. I doubt it is the problem you describe here but those filters have caused me a lot of trouble on cars, and the one on the lawn mower is annoying me now. Without looking at all dirty, they seem able to block the flow of fuel completely somehow.

Only since they are made in China.

 

A few other things I would also like to comment on:

 

- The fuel level in an aftermarket inline plastic filter has no significance whatsoever, unless it remains empty.

 

- Very few old yanks have a fuel return pipe.

 

- PM me if you need instructions how to test/adjust the auto choke.

 

- Ethanol content in petrol is a lot lower in the EU than it is in the US. In 99% of the cases it is not to blame

  for your running problems and the issues it very, very rarely causes are very, very typical and easy to fix.

  In fact, the chances any rubber parts made before they became Ethanol resistant still being part of your

  fuel system are very slim indeed.

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How much is a new Edelbrock? Sometimes old carbs don't want to be fixed - the Solex/Satan 4A1 DVG (Drecksau Verpiss Giftzwerg) four barrel is one such carb but I've had HIF SU's that I've given up on.

A brand new like for like 1406 performer is just under £400 direct from Edelbrock Europe. So not cheap!

The refurb sets I’ve ordered come to just under £130 so well worth doing this I think.

 

As Junkman said, the kits are basic gasket sets or a comprehensive refurb kit containing all gaskets, springs, needles and seats etc etc.

I’ve bought the comprehensive kit regardless as it contains the (imho) essential needles and seats. I’ve also ordered with it the pair of new floats with hinges (come separate from kits) and a ‘tuning kit’ containing various other bits and new jets.

My reasoning is that if I strip the whole lot down, clean it, and reassemble with everything new then it should cure the problem.

Last time it was only cleaned out and checked. It’s done it again now so clearly there’s still shit inside somewhere or the floats are fucked or the needles/seats are fucked. I’m spectacularly short of patience for shit like this so don’t fuck around anymore and just replace it all I think is the better option.

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