checking Lamda sensor for fault - Alfa Romeo Forum
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(Post Link) post #1 of 8 Old 14-10-09 Thread Starter
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checking Lamda sensor for fault

Hi Lads,

Is there a way to check if the lamda sensor is faulty? I know a few months back it had to be replaced as my emissions were way over the NCT (Irish MOT) limit, also I noticed there was a smell of petrol fumes when I got out of the car.
Lately the same symptoms are happening i.e. petrol fumes getting out of the car and two friends I had in the car said they could smell petrol fumes in the cabin
I know lamda sensors are crap anyway and tend to have to be replaced regularly but how can I check if it is faulty? Is there something else that can cause them to go?

Regards

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mo4
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Lambda wont cause a smell of raw petrol in the cabin or outside the car.
Check that the seal on the petrol cap neck is ok (does it give a whoosh when you open the filler cap? it should)
Also, lift the carpet in the boot and there is an inspection panel to allow access to the fuel pump pickup, which is a weak point on these cars.
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Agree a leak is more likely....

...but in case it ever helps, a fairly simple test for a Lambda just needs a cheap DVM. Track down the signal wires, dab the DVM across them then run the engine (leave the probe properly connected to the car). Once it's warmed up for a few moments, you should see around 1v to 4v on it. Blip the throttle, as long as the voltage reading swings quickly then settles back to a stable-ish figure, it's probably OK. If it doesn't change voltage, could be a heater supply problem, if it's very slow to react, it's probably poisoned and needs replacing.

Lots of things can damage a lambda. Leaded fuel poisons them fairly quickly, the wrong sort of silicone gasket sealant used almost anywhere on the engine can poison them sooner or later.

Good chance of a trouble light if the probe has gone as well.

HTH
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(Post Link) post #4 of 8 Old 17-10-09 Thread Starter
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Quote:
Originally Posted by mo4 View Post
Lambda wont cause a smell of raw petrol in the cabin or outside the car.
Check that the seal on the petrol cap neck is ok (does it give a whoosh when you open the filler cap? it should)
Also, lift the carpet in the boot and there is an inspection panel to allow access to the fuel pump pickup, which is a weak point on these cars.
Funny you should mention that Morgan, sometimes when I release the petrol cap I get a woosh sound, like as though it had created a vacuum that I released but only sometimes, mostly it unscrews without a sound
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Also check the rubber fuel feed to the injector rail...I had a strong smell of petrol in my car that was caused by the pipe perishing at the point the jubilie clip ran round it securing the rail...old age and overtightening had caused the rubber pipe to fail....unfortunately it had failed underneath so out of sight...took a while to locate.
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I have had this problem on two seperate cars.

On one of them a spark plug was loose (gave a ticking too from the engine) on the other the fuel vapour recovery solenoid had failed.

It is under the driver side wing at the end of those 2 light blue pipes you can see under the bonnet.

If you remove it and apply voltage it should activate. If not is is knackered.
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(Post Link) post #7 of 8 Old 17-10-09 Thread Starter
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Quote:
Originally Posted by jonjeffryes View Post
Also check the rubber fuel feed to the injector rail...I had a strong smell of petrol in my car that was caused by the pipe perishing at the point the jubilie clip ran round it securing the rail...old age and overtightening had caused the rubber pipe to fail....unfortunately it had failed underneath so out of sight...took a while to locate.
Cheers jon, can you be a bit more specific of where to look? where is the injector rail and how will I spot it?
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Quote:
Originally Posted by Alfa155 TS View Post
Funny you should mention that Morgan, sometimes when I release the petrol cap I get a woosh sound, like as though it had created a vacuum that I released but only sometimes, mostly it unscrews without a sound
The same happens to me too.
 
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