604 fails MOT on emissions

[dieselnutjob]

Basically it's idling very rich.  Odd as it passed in previous years and hasn't been driven much.

 

This is the wierd small Solex for idling and big vacuum operated one for power.

 

I am expecting it to be a nightmare to sort.

 

Anyone any ideas?

[scaryoldcortina]

Float height, float needle, choke.

 

Rich at idle is normally a flooding situation. Out of interest, how bad were the readings?

[dieselnutjob]

double the limit

 

it seemed okay until the computer told him to rev it a bit and when he did that it all went red on the screen.

 

Same tester bloke and computer as last year

[Asimo]

The same flaky carburettor setup as my Renault Alpine, which suffered from split vacuum hoses and gunk blocking air jets. Good clean and new tubes quite likely to sort it.

 

Oh, first check, is the choke going off when warm? My choke water passages bunged up (and eventually disintegrated) due to corrosion.

[Jim Bell]

  Odd as it passed in previous years and hasn't been driven much.

 

Anyone any ideas?

 

 

Itallian (or French) tune up?

 

If its not been used much, punt it around in 2nd for 20 mins before the test.

 

Garunteed* to help.

[Junkman]

Buy a diesel VW.

[scaryoldcortina]

double the limit

 

it seemed okay until the computer told him to rev it a bit and when he did that it all went red on the screen.

 

Same tester bloke and computer as last year

Wierd, non cat emissions are done at idle. You rev to 2000 to purge the system, then measure HC and CO at idle. You only need to rev further if CO is a pass but HC limits are not met - in this case you can rev to 2000 again and hold to see if the HC goes down.

[Lacquer Peel]

http://www.ebay.co.uk/itm/1991-LEYLAND-DAF-400-SERIES-CONVOY-2-5D-PEUGEOT-ENGINE-MILEAGE-54-961-/111804836642

[Clanger]

Give VAG a ring, I believe they have some software that may be of some use to you.

[michael1703]

Did he input the car age into his gas analyser correctly? The limits for your car would be about 4.5% co which most cars can pass

[dieselnutjob]

The car scored 9%

[Bren]

Can you get parts for the carb anymore?

 

I had a royale with a bitg solex carb that was knackered - clouds of black smoke and single figure mpg.

[Bren]

Regarding my earlier post about ten months into ownership I discovered the car had no air filter. It was like this for a reason.

 

Take pug's air filter out.

[Junkman]

The car scored 9%

 

If the car was really at operating temperature and actually running good while doing this, I would like to see the calibration certificate of the measuring device, please.

I'd also take the car to a garage and have them do a comparison test with their equipment.

If they confirm the value, I'd start on the ignition side of things - plugs, leads, cap, rotor, timing, dwell angle, vacuum.

 

Is that carb this tri choke Solex thingy with the auxiliary air valve and solenoid? 4A1 or sum such?

 

Also, what age is the tester?

[Asimo]

 

[Junkman]

Looks like a 34TBIA/35CEEI combination, like Alpine A310. Are there tags on them? Your problem is most likely with the 34TBIA, because that's the one for cold start/tickover/part load.
 

 

The 34TBIA (1) is operated by the accelerator pedal. During part of its travel, the opening of the 35CEEI (2) is mechanically blocked.
It then progressively allows the opening of the 35CEEI by means of a diaphragm activated by the pressure difference ​​between the two carburetors.
The mixture from the 34TBIA is heated by the manifold; it delivers mixture regardless of the engine load.

[forddeliveryboy]

double the limit

 

it seemed okay until the computer told him to rev it a bit and when he did that it all went red on the screen.

 

Same tester bloke and computer as last year

 

That's not the right procedure for this age of car, surely? if it was ok whilst idling originally then why was it revved? Were the %s as bad at 2000rpm? - the fuel consumption must be in the low teens, then?

 

Could be something sticking through lack of use or petrol which is past its best, the added ethanol makes it more likely to absorb atmospheric moisture as well as affecting seals and some plastics - fill with fresh and use with plenty of enthusiasm to get everything nice and hot. Bit awkward if the test's out, I know...  but do check the bowl isn't overfilling at idle.

 

If fuel consumption is as good* as usual and idling isn't lumpy-rich, then I'd suspect the computer or operator.

[Junkman]

So to make this perfectly clear, the 34TBIA supplies the engine from tickover, then during part throttle, as well as when the second carburetor springs into action.

It is thus likely the only one that operates when the emissions test is done, assuming 2000 OMGRPM are not exceeded.
 

The opening of the throttle valve is controlled directly and mechanically by the accelerator pedal.
It has a cold start valve, controlled by a wax thermo element in contact with engine coolant and this is what I would investigate first. If this isn't working properly,

it would rich up the mixture and you'd have excessive emissions.

 

 

 

The thermo element is part 39.

There is also a mixture screw, which is part 4.

[Junkman]

However, a small amount of mixture (15 - 20%) at tickover is actually supplied by carburetter 2, so it can't be completely ruled out as a culprit.

Basically, what they did is let the second carb contribute to tickover a little bit, to avoid judder under deceleration/overrun.

 

 

 

The only possible adjustments would be the idle air screw (20) and the mixture screw (21) in this illustration:

 

 

 

To be honest, I'd only touch this carb if replacing the thermo element/adjusting the 34 carb isn't sufficient.

[pshome]

... i have two of these beasts in the garage.

 

Let engine warm up and make sure the thermo choke is fully extended (no more increased idle speed).

 

Set idle speed to 950 rpm using the air screw on the 34TBIA, then adjust CO with the mixture screw. I set mine to ~ 1.5%.

 

If you cant adjust  to reasonalbe values, check the 34TBIA for broken seals ot diaphrags, the accelerator pump diaphragm tends to fail quite frequently.

 

Don't touch the double carb, as Junkman said, it is responsible for about 10% of the mixture even when not engaged, but that doesent play a role here. Anything you change there will make no difference to the idle CO but car will drive like shit.

 

CO will be very high at anything but idle speed. If the MOT guy insists on taking the CO measurement above 1000 rpm, then he does the testing wrong.

 

If all fails: come over here, my TÃœV guy sticks the tester nose into some other car and takes that record if needed

[Junkman]

If all fails: Try bigger hammer/smaller socket combination. On MoT tester, not car.

[scaryoldcortina]

Either carb flooding will also cause the same symptoms...

[Asimo]

Nnnng, this thread reminds me just what a bastard carburettors can be, especially if they are Zenith or Solex.

[dieselnutjob]

It's not that clear to me exactly what happened.  The tester is an experienced guy and has no incentive to fail it as it is a no pass no fee place.  Also they know me quite well in there so there's no fear that they think I'm from the ministry.

 

The car runs like crap anyway.

It will idle when stone cold and then as it warms it goes through a phase where it idles weakly (too slow, cutting out) and is virtually undriveable because you have to rev it to stop it stalling and sometimes there isn't enough torque to get it into D or R without stalling.

Eventually as it fully warms it then idles properly though goes through this speeding up slowing down cycle that lasts maybe 10 or 15 seconds per cycle.

 

When these cars were new all of the road test reports say that from a cold start that they would idle at 2000rpm which would slow as it warms.  Mine doesn't do that.  I don't see how on earth you would get it into D or R at 2000rpm.

 

I guess that both carbs need to come off to make sure that they are sealed to the manifold properly and and the small one will need to be cleaned up.

 

If that doesn't work I have a 38DGAS I can always put on.

 

Also the rear main crank seal seems to be pissing oil out but that isn't a fail.

[Des]

It's not just a bunged airfilter is it? Or all soaked in oil because of a blocked breather that's causing an oil leak to piss you off because it can.

[pshome]

The small water tube that provides heat to the automatic choke is the highest point in the cooling system. If water isn't going up there reliably, your choke goes crazy and you have the exact symptons you describe. Air bubble, not enough water, tubes clogged?