Question for the engine experts, what are the differences between 3.5 and 4.5 with D-jet? How much interchange in parts is there between the 2 systems? Iwondering if I could use the wiring harness, computer, etc. from a 4.5 on a 3.5. Someone mentioned the 4.5 has a MAF sensor and other differences...

I have '69 3.5 in a '63 111 220SE that was converted to CIS by the previous owner. But it doesn't run right at all, and it seems likely that they used 4.5 CIS injection part. I saw a complete-looking early 450SLC (euro lights & bumpers) in a local scrap metal yard and am wondering whether I should go scavenging...

Scott

Scott:

Injection system is identical on the 3.5 and 4.5. However, if someone used the D-jet heads with K-jet, you may have some problems, I don't think the injection ports are the same (I could be wrong here). Certainly, the block is the same for both engines, but crank and rods are different (higher compression on the 3.5).

What is the running problem? There are a number of problems that may cause running issues that are completely independent of the block/head combination (as in timing, bad MAP or temp sensors, etc).


Setting the ignition timing with a bad vac retard diaphram (or the vac disconnected) will cause very late ignition timing, stumbling, throttle lag, and terrible acceleration along with excess fuel consumption.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

As far as exchanging EFI components from a 3.5 to a 4.5 or viceversa . . . a common practice was to install the YELLOW 3.5 injectors in 4.5 engines as they flow more fuel.

I used to set the CO Potentometer at 10 clicks and obtain a 2.0% CO reading at idle by adjusting the CO at the PRESSURE SENSOR . . .

CO for idle must be set with the idle switch closed with the potentiometer and after main CO is set at load with the adjustment on the MAP-- the two circuits are separate but interconnected. 2.0 CO at idle will nearly foul the plugs, too, as well as reducing milage considerably....I'm keeping mine on the lean end of the scale so I can afford to drive it!

Peter

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I'm talking of 10 clicks on the ECU (middle of range) . . . throttle switch at IDLE STOP . . . 8 deg BTDC@750RPM . . . 2.0% CO . . . adjusted at the Manifold Pressure Sensor by removing the end cap and adjusting CO by the 4mm allen screw to shift the frequency time base . . .

Factory procedure is to unplug the idle switch/throttle switch and then set mixture at the MAP sensor-- range is 0.5 to 2.0 % -- then plug idle switch back in and set idle mixture with the screw on the ECU.

May not make any real difference, but it is also recommeded to set the CO at 3000 rpm under load as well.

2.0% is the top of the range, and will reduce milage from 15ish to 12ish (or less, if you have a heavy foot)!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Keep in mind that were talking about settings with different injectors installed . . . I'm referring to 3.5 injectors (yellow) installed in a pre- AIR 4.5 engine such as a 117 981, 982 and 983 pre-catylist versions . . .

Only a very few people were willing to pop for cash to do this. It gave moderately good results at lower mid range and only effected mileage when you had your foot down . . .

You're referring to a 3.5 without an idle contact in the throttle switch . . .