Running Rich?

[volvosneverdie]

Ok boys and girls, I think I may have a small problem. And could do with a bit of advice.

Im not very mechanicly minded/handed so i'll explain in laymans terms.

My 1.4 340 (carb) is going through petrol at an astonishing speed. Done about half a tank in less than 20 miles (ish).

Had a good scout round in my amateur manner and cant find any leaks or anything.

No smell of petrol anywhere that i can notice.

There is however a thick sooty build up inside the exhaust. Stick a digit in and it comes back black as your hat. Really thick too.

Scratchy Head.

Would a poorly adjusted carb drink this much juice?
Its the only thing i can think of really, and the car seems to be running fine.
No probs on the road, starting, idling or anything else that ive come across.

Any ideas people?

Much appreciated.

[Vart]

mine drank a lot of fuel when the hoses between the fuel tank (6 inch or so pipes under circular black plate in the boot) split - no obvious outside sign but smelt of fuel. perhaps worth checking both these two and the two between the fuel pump and the hoses under the car.

carb-leak wise perhaps worth checking the black fuel hose into the carb (lefthand side when in the drivers seat), the carb filter bolt facing the radiator. after that it things like float height, choke getting stuck on and similar - see haynes for that.

are the brakes ok? not getting stuck on or anything?

mine exhaust is full of black soot - i believe its a function of a carb as its best-guess for mixing as opposed to 'clever' electronic fuel injection. wouldn't worry - although when its running put your palm near the pipe and see if there are any black fleck being spat against it - this is soot and shows its over-rich.

does seem excessive consumption - mine mis-behaved for a while prompting various head-swaps and carb replacements recently. it was coughing black soot out of the exhaust , bad idle all sorts but even with this the economy wasn't ever much worse than 25mpg.

that said, in the current cold weather i'm not getting much more than 30mpg although i have just remedied a carb heater plate that was fairly warped perhaps causing an air leak.

that said - hole in the fuel tank - if your feeling rich - fill the tank up and see how much comes flooding out.

[volvosneverdie]

Thanks for all of that Vart, I'll get to poking round those areas with a lit match and see if I can spot any fuel leaks.


Only noticed recently because i filled the tank right up and two days later it was half full. Only did a handfull of miles in between.
Breaks are fine so its deffinatly not a problem eminating there.

So it must be petrol escaping somewhere, and we cant afford to let it just escape these days eh?

Many thanks.

[Vart]

it may just be the fuel gauge however, i'm fairly sure mine stays at full until theres about 6 gallons left then stays at half for another few gallons 3 gallons is around 3mm from the reserve mark and the reserve 5 litres is anyway between there and somewhere after the bad end of the dial. i only notice the gauge at these 4 ish points...

one day i'm going to empty it and compare reality (quarter fill then half fill) with the gauge - i suspect reality will be quite different.

ambient temperature alters the reading lots too (i find anyway).

[volvosneverdie]

Hadnt even considered it being an innacurate reading vart, so cheers again.

i'll check the tach and see how many miles I get through til the fuel gauge reads almost empty and see how true the reading actually is.

Cheers again man.

[jtbo]

It is few years since I had full tank on 360, but I believe it likes to go quickly to middle and then stay there for good time, until it starts dropping again.

But I had to bend fuel sender arm a bit to get it read empty when tank was empty as it did like to run out of fuel before reaching reserve or lamp getting lit and that was bit of nuisance.

[volvosneverdie]

Cheers Jtbo.
With no smell of fuel anywhere, it seems to indeed be an untrue reading.
(i hope).

I'll know for sure when ive done a tank full of miles i suppose.

[pettaw]

Check the fuel hoses from tank to engine, they won't smell until you've filled up very full, and then you'll get a smell of fuel from the back, or even leaking if they're really perished. They go in the expansion tank, and also the sender unit. There's loads of threads on this, do a forum search and you'll find chapter and verse on where they are and how to replace them.

Carb adjustment is another possibility. High consumption is a possible indication that you're not running right, either rich or lean strangely enough because the car isn't running properly you have to try harder etc so it still uses more fuel. Check for air leaks, and then check the carb adjustments. Again forum search for the how to's for the Weber carb and how to check for air leaks, but do check for air leaks first.