BMW Bosch L-Jetronic Fuel Injection - Strip-Down / Maintenance Guide + Diagrams [E30, E21, E28]

Throttle Housing:
1. Disconnect the cables (1, 2 or 3) as applicable - Fig. 1.
2. Pull off the vacuum hoses, the coolant hoses (1 and 2) - allowing the coolant to drain - and the air hoses (3 and 4) from the throttle housing - Fig. 2.
3.Remove the vacuum hoses (1 and 2), and the air hose (3) and pull off the multi-pin plug (4) - Fig. 3.
4. Remove the fixing nuts and take off the throttle housing. Do not separate the throttle switch from the housing, as a special gauge will be required to adjust it when refitting.
5. Refitting is a reversal of removal. Use a new gasket and bleed the cooling system.

Throttle Vacuum Control:
1. Pull off the hose (1), release the nut (2) and remove the vacuum control (3) - Fig. 4.
2. When refitting, adjust dimension (B) to between 32.8mm and 33.2mm (1.291" and 1.307") using screw (4).
3. Adjust dimension (A) to between 2.6mm and 3.0mm (0.102" and 0.118") using screw (2) - Fig. 5.

Control Unit:
1. Open the glove compartment and pull the pins from the retaining straps.
2. Remove the screws and place the glovebox cover to one side.
3. Depress the retainer (1) and pull out the multi-pin plug (2) - Fig. 6. Remove the control unit.

Air-flow Sensor:
1. Release the clamp and pull the duct from the air-flow sensor.
2. Disconnect the multi-pin plug, unscrew the fixing nuts and withdraw the sensor.
3. Refitting is a reversal of removal. Renew the seal if necessary.

Temperature Time Switch:
1. Pull off the plug, then unscrew and remove the switch.
2. Refit the switch using a new sealing washer.

Coolant Temperature Sensor:
1. Pull off the plug and unscrew the sensor. Refit using a new sealing washer.

Cold Start Valve:
1. Pull off the plug (1) and disconnect the fuel line (2) - Fig. 7.
2. Unscrew the mounting bolts (3 and 4) and withdraw the valve.
3. Use new seal when refitting.

Fuel Injectors:
1. Unscrew the four injection tube bolts and push the tube upwards until the fuel injectors have cleared the guide in the intake manifold.
2. Pull off the plug (1) and take out the circlip (2) - Fig. 8.
3. Take off the fuel injector.
4. Refitting is a reversal of removal; use new O-ring seals.

Throttle Shaft Return Springs:
1. Disconnect the throttle, kick-down and cruise-control cables. (The latter two where applicable.)
2. Remove the retainer (1), washer (2) and disconnect the linkage (3) on the lever (4).
3. Raise the lever and turn it to relieve the spring tension.
4. Remove the lever.
5. Remove the spring.
6. Disconnect the spring (1) and unscrew the nut (2) - Fig. 9.
7. Remove the washer (1) and lever (2) - Fig. 10.
8. Remove the sleeve (1) and spring (2) - Fig. 11. - also the wave washer.
9. Reassemble in the reverse order to dismantling and adjust in the following way - Pull off the tamperproof lock (1) and loosen the screw (2) until the lever (3) no longer rests on the screw - Fig. 12.
10. Place a finger on the lever and tighten the screw until the lever just begins to move. Turn the screw a quarter-turn more and refit the tamperproof lock.
11. Adjust the throttle, kick-down and cruise-control cables (where applicable).

Injection-system trouble-shooting guide here - https://www.beemerlab.org/2020/12/bmw-bosch-fuel-injection-system-trouble.html

Bosch L-Jetronic injection-system overview / diagram here - https://www.beemerlab.org/2019/11/e30e28e34-bosch-l-jetronic-fuel.html

E30 Stance - Steel wheels or modern wheels??

E30 wheels is a magnificent topic of discussion, so lets have a couple of different takes on wheels for the old 3er...

By far the most common wheels to bestride the E30 are cross-wire / BBS styles. and beyond that owners tend to stick to solid period styled alloy wheels like Azev-A five-spokes or Borbet C. Personally I think the old-school BMs look best with steel-wheels such as the almighty Weller competition wheels, as in the pic above, especially with a lowered car. These are built for heavy-duty dirt-track racing and off-road and I think give a lowered E30 the best squat / rat look.

At the other end of the spectrum, here are some ultra-modern Japanese-style alloys on a 325is. I am not 100% on who makes these, but they look very much like RAYS Volk or Rota wheels. You don't see many wearing rims like these, certainly not done well anyway, but why not? Sharp lines suit sharp lines and the 3-box shape combined with large modern alloys gives the E30 a very purposeful look and go-kart stance.

BMW UK Advertising Poster / Placard 1980 - M1, E21 320/6 + 6-cylinder engines

Nice 1980 placard from BMW UK advertising their family of 6-cylinder engines, from the later E21 320 to the M1's M88 and explaining the benefits of the. "Six cylinders where you'd expect to find four." in the compact 3-Series and "Six cylinders where you'd expect to find twelve." in the case of the supercar M1.

   BMW's dedication the six cylinder engine is not a recent phenomenon.

   It goes right back to BMW's original as a specialist engine-maker, rather than a car manufacturer.

   In fact, the first engines we ever built were six cylinder aircraft engines.

   Later, in the 1950's when conspicuous consumption was almost a status symbol, BMW preferred to stay with efficiency rather than extravagance and launched a six cylinder luxury car.

   Today, in the BMW 320, a car that's scarcely more than 14ft long, theres a sophisticated six cylinder power unit.

   And the BMW M1 on the right also needs no more than six cylinders. Even though in its most developed form, the engine can actually produce 800 bhp.

   It's not a blind dedication to six that makes us refuse the false economy of a four in the case of the 320. Or the wanton extravagence of a 12 in the case of the M1.

   Rather, we take our guidance from the laws of physics.

   According to those laws, it is not possible to build an engine that's perfectly balanced with less than six cylinders arranged in-line.

   Anything else, is a compromise that may help a car manufacturer balance its books. But won't help it balance its engines.

   Which is why every engine BMW make that's two litres or larger, is an in-line sic cylinder engine.

   Fortunately, there's no need for you to understand the laws of physics to discover the difference this makes.

   There's not a trace of roughness as you cruise. Or rawness as you accelerate.

   There's a smooth immediacy which motoring journalists normally describe as "turbine-like".

   And there's a flexibility which makes driving in traffic almost a pleasure. For with 85% of maximum torque at a mere 1900rpm you get a responsiveness in fourth gear that you might normally expect only in second gear.

   The BMW 320 costs £6,790.

   Which is scarcely more than cars whose manufacturers have chosen to compromise on their engines.

   And if they're prepared to compromise on the most important part of a car, where will those compromises stop?

BMW M54 Engine Wiring Harness Diagram Illustration

Illustrated diagram showing the engine wiring-harness configuration on BMWs with the M54 6-cylinder petrol/gasoline engine family, showing connections to the Vanos, GCV, DISA Valve, etc.

“TIP: Ensure your CCV system is properly connected to the underside of the intake-manifold (and it is not damaged) before connecting all of these harnesses. It’s a huge pain trying to reach through all the wires to adjust or properly connect it.”

A different take on a wiring-harness diagram done in a hand-drawn artwork style, but useful none-the-less, so it had to get catalogued. Originally posted by u/feedthedonkey on the r/BMW Tech subReddit, who claims credit for the artwork.