ELECTRONICS vs MECHANICAL SYSTEMS

ELECTRONIC IGNITION vs POINTS & CAPASITORS
The preferred system is of course the electronic one. We've all been told about benefits like reduced fuel consumption, reduced emissions, improved performance, and no need for maintenance. The only true story here is maintenance freedom. Correctly adjusted points gives exactly the same engine performance as electronic systems. For a while, and then the dwell angle and timing must be adjusted again. In the mean time, performance suffers and consumption rises. This is why electronic ignition really is the preferred system.

FUEL INJECTION vs CARBURETTORS
A higher peak performance, better fuel economy, cleaner emissions, the list of advantages for a fuel injection system is long and convincing.
And yet, no injection system can match the beautiful throttle response of a good carburettor setup. Nor can it match the sweet torque-delivery in the lower part of the rpm-scale. Especially noticable with automatics, as their engines spend most of the time in the 1500-3000 area. The carburetted GLsA has more ooomph than the GLE. An EMS is more sluggish at low revs than a GLs, but pulls away at higher revs.

All single carb 99's were equipped with the British ZENITH STROMBERG CD 175 carburettor, used by dozens of other car manufacturers (including Volvo).
The "S" engines got two smaller CD 150 units. The numbers referre to the throttle opening, measured in inches. CD 150 = 1,5" = 38,1 mm. CD 175 = 1,75" = 44,45 mm.
These carburettors give the engines very nice characters, but require frequent fettling in order to maintain the correct setting.

In addition to the Saab related workshop manuals, Haynes can supply books on carbs. I'll just add one remark to the service manuals from Saab and others who installed Zenith Stromberg carbs (meaning Volvo). Many of them claim that you should regularly check the carb's oil level and top it up with.... carburettor oil??? There is no such thing. Periode. What's inside the little one-point-five-decilitre-cannisters labelled "carburettor oil" at the petrol stations, is AUTOMATIC TRANSMISSION FLUID. At ten times the price!

If we read the service manuals from other British cars of that periode (Triumph, Rover, Vauxhall), we'll see that they reccommend topping up the carburettors with ENGINE OIL. The very same oil you put in the engine.
The purpose of the oil is damping the carb-piston's up-and-down-movements. If the oil is too thin, the car will be jerky at low revs/constant speed, and starve during accelleration.
Which is exactly the same symthoms you get when the carburettor oil level is too low...

PASSING THE TEST
Every now and again, your car must be dragged to the local car-clinic (MoT, Tüv, EU-test, SBP...), to check if it's roadworthy. Engines soaked in oil seldom passes, cleaning it is a very good idea. Do it at least two hours before the test so the water doesn't give you away.
The largest concern in these tree-hugging times, is emissions.

Two important things is worth noticing:
- The ignition system must be in top shape.
- The oil must be changed, preferrably the same day as the test. Unburnt fumes enter the induction system via the crankcase vent hoses, and gives a higher CO reading.

If the engine is otherwise in a good condition, your only worry will be the fuel system. The K-jetronic injection seldom causes any trouble, but carburettors require more attention.
- The air-filter must be brand new. On carb-engines a clogged filter chokes the carburettor, resulting in high CO read-outs. You may renew it on an injection-engine aswell, but all a dirty filter does, is to reduce power output.

The problem with these carburettors is that they sometimes wont co-operate when you try to adjust them. The reason is simple: They are worn, and need to be dismantled for a good cleaning, a new set of gaskets and new metering needles & jets. Which you should do if you intend to keep the car for a while. Then you wont have to worry about carburettors for the next ten years or so. Hahaha! What I meant to say was that new needles and jets are required every second or third year, which is exactly the same interval as the brake fluid and engine anti-freeze should be changed at.

My car has a twin-carburetted B-engine, which I don't intend to keep for very long. It runs fine, but I suspected the CO to be a little over the limit, and therefore checked it a few days before the test. Six point something. Ouch! A minor adjustment resulted in five point something. I still didn't want to spend time and money on a carb-overhaul, this required some latteral thinking... Then I remembered something I once read about emission legislation in Central-America. Their fuel is a mixture of 85% petrol and 15% ethanol. This reduces performance by 10-15%, but does wonders for the CO read-outs. Ethanol is the kind of alcohol we drink.
At the day of the test, I made sure the tank was nearly empty, filled her up with 10 litres of petrol and gave her 1,5 litres of booze. The test-mechanic didn't comment the funny smelling exhaust fumes and the car passed, with a CO of 3,6% ! (Hehe!)