We sell used, good ignition parts for BMW E30 3-series cars such as the 1984-1991 318i, 325, 325e and 325i.
We like to understand what we sell. We would like you to enable you to also understand what you’re buying. So, I put together a sort-of-chronological flow of the events and the roles that the components play. Each component mentioned below, we sell — except for the rubber fuel hoses, fuel filter, air filter and catalytic converter.
To me, the center of the action is the fuel injector. It sprays gasoline into the airstream trigger by an electrical signal. Let’s break that down:
- Electrical signal
Isn’t it nicer to have this logically laid out like this?
1. Electrical signal
Perhaps the most upstream parts of the electrical signal begins with the various electrical signals that are sent to the fuel injection computer.
- Crank-shaft position sensor
- Outside temperature sensor
- Engine temperature sensor
- Airflow meter
- Barometric pressure sensor
- Oxygen sensor
The engine wiring harness transfers the signal from the sensors to the Motronic computer, and from the computer to the fuel injectors. On some models, the last section of wiring, that attaches directly to the fuel injectors, is separate.
The above shows the main electric components for fuel injection.
But, the fuel pump relay is also essential. The fuel pump is not always on. It gets its on / off signal from the fuel pump relay. We also sell the fuel pump relay.
The most upstream part of the fuel flow begins at the gas cap. From there, the fuel flows into the fuel tank itself.
To figure the level of the fuel in the tank there may be one or two fuel level sending units, depending on the model. These units trigger the low-fuel warning light also influence the position of the indicator needle on the dashboard.
Depending on your car using the two-unit wiring or the one-unit wiring, there are two different types of fuel gauges. They have to match.
The fuel gauge is fairly isolated from the rest of the instrument cluster. If you need to replace only the fuel gauge, it’s not that difficult. You do not need to replace the entire instrument cluster.
Depending on the model of the car, it might have one or two fuel pumps.
If there are two, then the in-tank fuel pump pressurizes the fuel lines to prevent vapor lock, and the main fuel pump is then mounted below the car. If there’s only one, then it’s in the tank.
A metal cradle is bolted to the underside of the car, that houses the external fuel pump and the fuel filter.
In snowy areas where they salt the roads, E30 owners might also be concerned about the metal fuel lines that supply fuel from the fuel pump forward to the engine compartment, and back to the tank.
In the engine compartment, the fuel hose enters the rear of the fuel rail.
Into that fit the six fuel injectors.
At the front of the fuel rail is the fuel pressure regulator that limits the flow back to the gas tank, so as to maintain the fuel rail and the fuel injectors at the optimal pressure.
3. Air flow
The most upstream part of the air flow begins at the plastic plate right behind the headlights.
The plate has a hole into which fits a plastic funnel.
Downstream of the funnel is a rubber hose to guide the airflow into the air cleaner box.
Downstream of that is a rubber hose to guide the airflow into the air flow meter.
Next, the air flows through another rubber hose into the throttle body. We To prevent the throttle from icing, water hoses are routed to the throttle body and back, to heat it.
Arguably part of the airflow big picture is the accelerator cable going from the pedal to the throttle body.
From the throttle body, the air flows into the intake manifold. That’s the huge aluminum part that’s on top of the engine.
Air flows mostly through the throttle body but to keep the engine idling when the throttle is closed, there is also an idle control valve. A little green computer box controls that valve.
Downstream of the engine are the two exhaust manifolds.
From there the hot exhaust gas flows into a y-collector, then the catalytic converter, then the exhaust pipe and the muffler which stays up thanks to some rubber hangers.