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From: ben thongsai <>
Date: Fri, 27 Dec 1996 03:55:35 -0600 (CST)
Subject: Re: L-Jet to Motronic conversion

> From:
> Subject: l-jet to motronic conversion
> Hi guys - does anyone know how difficult it would be to convert an l-jet
> 530i to Motronic fuel injection? Has anyone done it before? What parts would
> be needed? What potential benefits are there to this converion? Is there a
> better year to lift the injection parts from?

As with most anything, it can be done, given the right amount of money, time, and expertise. The parts you'd need would, at the very least, be:

        Harness and ECU
        Air flow meter
        Crank sensors and a transmission bellhousing to match
        OR the front crank sensor and toothed wheel, if you're using
                a later Motronic
        Proper injectors (need to match internal winding resistance as
                well as flow rates)

You could cobble it together with the existing intake manifold and distributor, although it wouldn't be very pretty. Ideally, you'd also need the upper timing cover/distributor cap/etc., intake manifold, throttle body, thermostat housing, etc. to make everything fit nicely.

I'd guess that the Motronic 1.0 Adaptive system from an '85-'88 3.5L car would be the easiest and most effective system to retrofit. For the large headache you'd get trying to make everything work, you'd get a slight increase in power, better driveability, slightly better fuel economy, and lower emissions.

> Can one go a little further in time and use the injection from the newer
> BMWs?

Anything is possible, but if you feel the need to retrofit a later injection system (the 530i system is giving you grief, isn't it? -- I've been through a couple of them at just would not run right), the system off of a '79-81 528i or '80-'81 633/733 would be best. It's a simple harness/injector/brain/AFM swap. The car will run leaner, more power, etc.

> I'm guessing one would need: harness, computer, air flow meter, distributor,
> intake manifold, throttle body, numerous sensors and valves, TDC sensor,
> fuel pressure regulator. Can the e12 injectors be reused?

The 530i injectors are unique in that they run with a resistor in series with the wiring to reduce switching current. So they probably will not be useable with any other setup.

If you're considering doing a Motronic swap, it's a much better idea to just purchase a 3.3 or 3.5 motor complete with the Motronics and install the whole thing. It wouldn't cost much more than trying to piece together just the injection system, it'd be a lot easier to install, and you'd gain all of the benefits of a larger, late-model motor.

Hope this helps,

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