Evolution of Fuel, Ignition and Emission Systems
Thursday November 29, 2001 marked last year's Technical Session, held at the Cambie Road location of Don Docksteader Motors. Our host for the evening was Jason Leber, Volvo Master Technician. The evening was attended by about two dozen members. Jason's presentation was like a walk down memory lane, from low-tech to high-tech. In some ways, the evening was an continuation of Jason's presentation at the meet this past August. Jason has been with Docksteader Motors for 7 years and previously worked for an independent Volvo repair shop in North Vancouver. He holds the title Technical Specialist.
Ten years ago, most of us were unaware of carbon monoxide (CO), carbon dioxide(CO2), nitrogen oxides (NOx), and hydrocarbons (HC). Now, with AirCare emissions standards testing, many of us have become all too familiar with these terms. The first part of the evening dealt with fuel and ignition systems. Four living demonstration cars were displayed and tested using an exhaust gas analyzer (EGA).
The second part of the evening covered car electrical systems, and in particular, new Controller Area Networks or CAN systems. Automotive electrical systems have changed more than anything over the last 30 years. This section will be covered in a future edition of the newsletter.
All of us know and love the simplicity of the older cars. Practically anyone could understand and work on the fuel, ignition and electrical systems. They were reasonably reliable, produced acceptable performance results and could be fixed or adjusted at the side of the road with a pocket full of tools. And, there were lots of adjustments to play with. But, times have changed. All of the systems have changed and now it requires a whole new level of tools and understanding to diagnose and repair the new systems. Many of you have probably said, "Things just aren't like they used to be", or "I remember when..." Influences that have driven the change include the reduced cost of highly integrated digital electronic control systems (sometimes called MCU, ECU, computer, control module), increasingly stringent emissions regulations, and customer demands.
We looked at four cars of varying ages and levels of complexity. The first was a 1980 DL wagon with a B21A. This was the simplest of the four. It featured an SU carburetor, points and capacitor ignition. This was the most basic Volvo of this year. The next vehicle was a 1982 GL with a B23E. This was the same generation as the 1980, but a slightly more advanced car. All GL, GT, GLE, Turbo and GLT of this era use Bosch K-Jetronic fuel injection and (normally) Bosch electronic ignition. I can speak from experience that this setup is extremely reliable. The next was a 1990 740 with a 16 valve B234F engine, LH-Jetronic 2.4. This fuel system uses feedback in the form of an oxygen (O2) sensor, and pulsed injection. The fourth and most advanced car was an S70, with a five cylinder engine and sequential fuel injection.
Using the exhaust gas analyzer (EGA), Jason demonstrated the improved emissions over the years that the four cars were made. The first car, the 1980 DL produced the most CO, by far. CO is a product of incomplete combustion and is itself a fuel. If you starve fuel of oxygen (too rich) then you end up with an increased level of CO. This means that your fuel is not being put to the best possible use and has not completely burned. The DL produced 3.6% CO. The distributor functions to control the primary of the ignition coil and select the appropriate cylinder for spark. It takes care of absolute timing, timing advance and dwell.
The second car, the GL, turned out better emissions results with 1.4% CO and 100 ppm (parts per million) HC. This K-Jetronic system first showed up around 1974 or 1975 and became much more popular in the 1980s. It is completely mechanical and produces a continuous injection of fuel into the airflow just outside of the intake valve. The ignition system uses no points instead a "no touch" pickup in the distributor. This connects to the ignition module which controls a conventional ignition coil. The spark is then distributed to the four cylinders using a rotor in the distributor. This system was discontinued in Volvos in 1984. It should be noted that the 264 and Turbo models had a variant of this system, sometimes referred to as Lambda or KE, thus the familiar Lambda symbol "λ" on the grille. It used an O2 sensor to complete a control loop in order to maintain the proper mixture. The balance of the system remained unchanged.
The 1990 740 was the first of the four to use a true "electronic" injection system, using a control module that is the "brains" of the system. This LH 2.4 system was the second LH system, the first being LH 2.2. LH 2.4 was first used in 1989 on all models except for Turbo, with the Turbo following in 1990. The LH 2.4 system came with a diagnosis centre, allowing service personnel and owners to play doctor when something goes wrong. The LH systems use an O2 sensor to regulate mixture and a catalytic converter to "finish off" any CO, HC and NOx. This results in very low emissions: 1 % CO and 20 ppm HC. The term LH comes from Lambda Hotwire. Air flow is measured by an air-mass meter, an instrument through which fresh intake air is drawn. Inside the air-mass meter is a heated platinum wire which is cooled in proportion to the air flowing over the wire. The signal is passed on to the ECU which controls the injectors.
The final car, and with the lowest emissions, was the S70. This vehicle makes use of two O2 sensors, one on each side of the catalytic converter, and falls into the category of Ultra Low Emissions Vehicle or ULEV. The second sensor does not play a role in mixture adjustment but merely acts as an alarm in the event of catalytic converter failure. Aside from a transient reading at startup, the emissions from this car leveled off at 0 and 0 for CO and HC. Jason notes that this is vehicle is the most complex electrically and had to be to achieve such high efficiency.
Pros and Cons
There are many opinions on the evolution of fuel, ignition and control systems on Volvos. On one hand, the older cars can virtually be repaired anywhere with only a handful of basic tools. There is no diagnostic connector on a 122! These systems were reasonably reliable and performed adequately. On the other hand, the newer cars are too complex for the average backyard mechanic to either understand or diagnose, apart from changing oil, brakes, tires... Parts for the new cars, although very reliable, tend to be costly. Service is likely to require highly specialized tools for diagnosis. There is virtually nothing to adjust except the position of the driver's seat. So, what are the advantages? Lower emissions (AirCare subscribers like that), better fuel economy (one member claims his 3 litre 960 has the best fuel economy of any Volvo he has owned), better performance, built in diagnosis, ease of repair (by dealership). Certainly, eliminating adjustments simplifies the service process. On the Volvo S80 a major service consists of replacing the air filter and spark plugs, and vacuuming and washing the car.
Personally, I don't miss the poor performance of my old 1980 DL B21A when compared to my 1980 GT B21F. Fuel injection and electronic ignition has given the car much more performance and lower emissions. Emissions are usually better than the carbureted cars, but in my case I am suffering from a faltering fuel distributor, so it's only a matter of time before this needs to be replaced. The K-Jetronic system is quite reliable, but still there are components to fail. And, older systems can have vacuum leaks around the injectors and can be difficult to start once hot.
About Catalytic Converters
The catalytic converter is inserted in the exhaust stream a short distance from the engine. It's purpose is to break down undesirable components of incomplete combustion: CO, HC and NOx. Converters are fed with exhaust which is nominally 0.5% CO, and reduces CO typically to near zero. The oxygen sensor is inserted into the system upstream from the converter and regulates the mixture to maintain as close as possible to 0.5% CO. The catalytic converter is filled with a catalyst such as platinum or palladium in a physical form which maximizes surface reaction area. They typically last 10 years or more but can be compromised by exhaust which is laden with oil or antifreeze or which is too rich. Volvo original equipment replacements are in the $1200 range. Would you also like that installed? You might be tempted to go for a cheaper replacement from an exhaust franchise. We were warned that you might be greatly disappointed by the shorter than expected life of inexpensive replacements. By the way, newer Volvos are equipped with three-way converters. Two-way converters do not treat NOx.
Hints and Tips
Jason pointed out that the Pulsair lines must be blocked (plugged) during adjustment, otherwise the mixture will end up being too rich.
Many of the older engines are prone to knocking while under load, especially when using lower grade fuels. Jason noted that the springs holding the advance weights inside the distributor become weak with age, allowing the timing to advance too far. This extra advance, combined with other factors, produces the undesired knocking.
One of the common failures on the LH system is a faulty air-mass meter or a poor electrical connection to the unit. If the air-mass meter is faulty it may cause the car to stall immediately after being started. If the electrical connection to the air-mass meter is poor, you may experience very poor performance. This can be rectified by cleaning the electrical connection with WD-40 and repeatedly inserting and removing the connector. Complete failures are most frequently caused by excess intake air temperature. A mixing thermostat in the air box blends cool outside air with hot air taken from a heat exchanger on the exhaust system. If the thermostat fails it may deliver hot air only, thus damaging the air mass meter from the excess temperature. A new air-mass meter will run $500 or so, much more expensive than a $50 or $70 thermostat.
Oxygen sensor failures will almost always be brought to your attention at the exit lane of AirCare. Replacements are typically $350. There are two types: voltage producing and resistive.
LH 2.4 systems, starting in 1989 (1990 for Turbo models) come with a diagnosis centre. This small module, located close to the brake servo, has an indicator light and a small jumper which can be plugged into a number of sockets. Socket number 2 is used for fuel system diagnosis, 6 for ignition. If the air-mass meter has been disconnected (not a normal occurrence in driving, but possibly similar to a broken unit) then the associated code 1-2-1 will be flashed by the light once the jumper is plugged and the button pressed for one second. Successive codes can be read by simply pressing the button once after each code. The error codes are stored in a circular buffer, so eventually the first code will again be displayed. Once the first code has been presented again, the button is pressed for 8 seconds and then released. When the light comes on again, press and hold for another 8 seconds to clear the faults from the register. At this point, pressing the button again should reveal no fault codes. A complete list of fault codes can be found on a separate page.
Starting in 1998, legislation mandated the use of warning systems to indicate a breech in the fuel tank seal. Since the fuel tank is loaded with fuel vapours (HC) it is important to make certain that these vapour do not escape unnecessarily. They are normally absorbed by the evaporation control system. The tanks operate under slight pressure. So, when you stop by the neighborhood town pump, and the attendant cross-threads your fuel cap, you receive a warning light on your 1998 or newer Volvo. The sad news is that you now need a trip to the dealership to shut the light off.
In the newer models, 99% of all " Check Engine " light warnings are for emission faults or failures.
Part 2, a continuation of this technical session, can be found here.