PeachParts Mercedes-Benz Forum - View Single Post - Working on 104 vs. 103, how much difference?

suginami · #5 04-25-2003, 08:28 PM

This engine debuted in the W124 chassis in 1993.

Mercedes didn't change the badge this year, so it simply reads 300E, even though it has the 3.2 liter engine.

In fact, all 1993 300E sedans, coupes wagons, and cabriolets have the 3.2 liter engine.

Mercedes also installed the 2.8 liter M104 engine found in successive C280's in 1993, and called this model (correctly) 300E 2.8.

I might also point out that all 1993 300E (3.2's) share the same chassis #, engine #, and VIN # as 1994-1995 E320's. All of the interior changes occurred in 1993 (passenger side airbag, flip-up armrest, etc), but 1994-1995 W124's got the updated grill and headlights, chrome strip on rear trunk, clear / red tail lights, and clear / yellow front indicators.

I find the 3.2 liter engined W124's to be far superior to the earlier M103 300E's. The M103 engine has a single over head cam, and still used the CIS-E fuel injection system, using a distributor with one coil wire and 6 spark plug wires. This is basically a mechanical injection system with electronic control.

The 3.2 liter M104 engine was used in all 1994-1997 SL 320's, 1993 W124 chassis 300E/300CE/300TE (3.2), '94-'95 E320's (W124 chassis), 1996-1997 E320's (W210 chassis), and 1992-1999 S320's (W140 chassis).

The 3.2 liter M104 engine uses a different ignition system - HFM (hot-film mass air flow sensor), fully electronic, with integrated electronic ignition and sequential fuel injection. This system combines fuel injection and ignition control in one module. HFM-SFI systems use coils that are mounted directly on the spark plugs, replacing the distributor at the front of the engine. Each coil pack provides spark to two spark plugs at the same time, one connected directly to one plug, and the other with a short high tension lead to the next spark plug. So there are 3 coil wires and 3 high tension lead wires.

HFM fuel injection systems are designed so that idle speed can't be adjusted. Idle speed is completely controlled electronically. This HFM injection system also has adaptive technology that compensates for conditions such as engine wear and unmeasured intake air and is designed to maintain driveability as the engine ages.

HFM-SFI can retard engine knocking to just the knocking cylinders, unlike EZL technology, which retards spark timing across the entire engine. This keeps the ignition timing point as advanced as possible for maximum power output.

The 3.2 liter M104 engines also have variable valve timing on the intake cam, making the torque curve broad and flat, developing HP at a much lower rpm. This makes the power much more useable and noticeable.

The M104 engines also have a superior head design. Valve guide wear has always been a problem on M103 engines. The M104 head design has minimal vave stem/quide side force [ cam-valve swipe] . Mercedes seems to have solved the common M103 valve guide problems with this far superior design and it is not unusual to see them still tight into the 200K figures.

The early 3.0 liter 12-valve M103 engines are nice, but the advancement of technology is just so great in the 3.2 liter M104 engine, making these later cars much more desireable, IMHO.

I might add, however, that some seem to believe the M104's to be more trouble prone or expensive to operate because of two very common repair issues on the early versions of the M104 engine from 1993-1995:

1. The early head gaskets were bad, leaking oil at the right, rear corner of the head gasket. Techs have mentioned that this failure is much more commone on the M104 engine than the M103. Luckily, the head gaskets have been redesigned with copper or steel inserts, and the new head gaskets don't leak.

2. The early engines (1993- early 1995) have bad engine wiring harnesses, where the insulation on the wires flakes off, causing driveability problems, misfiring, random engine fault codes, etc. Budget about $500 for a new harness.

Except for those two issues, these cars are nearly perfect, IMHO.