Reset Computer on 602??? - PeachParts Mercedes-Benz Forum

350SL4spd · #1 08-25-2004, 06:03 PM

How does one go about resetting the computer on a '91 602 motor? This motor was run w/o oil until it seized (or the computer shut off fuel, as I now suspect, only the rod bearings were frozen). It purrs like a kitten at idle, but runs totally like crap (won't go over 2k rpms in Drive) unless you unplug all the wiring on the Fuel Injection Pump. Then it runs fine (no smoke even!), but of course has no boost or fuel enrichment, so it is too sluggish to drive on the road (0-60 in about 3minutes).
My thought are that when all the sensors went haywire as the engine was running w/o oil and heating up the computer freaked and shut everything down, saving some of the motor. However, it has yet to realize that everything is OK now!!!!!!!
How do I convince her of this?!?!
Thanks!
-Matt-

(Also: Does this explain the the vacuum in the intake manifold???)

TimFreeh · #2 08-26-2004, 08:21 AM

The ECU in the 2.5 turbo is only responsible for boost control, idle speed correction and EGR operation, it has no direct control of fuel delivery. I don't see the ECU would have any idea your car was running without oil pressure.

I don't think you can "reset" it like your PC - the ECU does have a self diagnostic capability using an impulse counter. It sounds like the boost control function is not working.

350SL4spd · #3 08-26-2004, 12:29 PM

There are two electronic controls directly on the injection pump. One is a control rod sensor and the other is related to the govener. They both trace back to a control unit and w/ these unplugged the car at least does not go into a fuel shut off mode, which must be desiginated by this control unit.
I was wondering if there was a way to reset it like you would to erase an CEL on a gasser. (or any other suggestions, at all)
-matt-

Grdenko · #4 08-26-2004, 02:22 PM

to reset the trouble codes, you put a wire into hole #4 on the "x-11" unit (the little box in front of the battery with a black plastic cover on it) 12 to 16 guage wire. then you touch the wire to a good ground for at least 10 seconds (best place is where the neg battery terminal is bolted down).
if you want to check the codes, you need a multimeter, but its not necessary to just reset the codes.

if it turns out you need a new computer for some reason, ive got a spare one i can sell to you fer' cheap.

later

gsxr · #5 08-26-2004, 03:27 PM

Hmmm. I'd wonder if it's opening up the EGR at the wrong time - that would make the car run pretty crappy. Let us know if the reset works that Grdenko described.

Grdenko · #6 08-26-2004, 05:20 PM

good point. if the egr is opening at the wrong time, its possible that the EGR and intake control flap vac lines are switched. it would be easy to do since theyre the same length and are right next to eachother. i think that would couse those symptoms, but that could only happen if you or someone else had been working on the vac lines.

TimFreeh · #7 08-26-2004, 08:09 PM

Wbda

Your IP indeed does have two electrical connections - one is for the control rack position and the other is responsible for idle speed correction. Both will trace back to the EDS control module if you follow the wires.

Do you have any technical information that validates your position that the EDS computer is responsible for regulating fuel delivery in your car? I'd love to see a reference to it - If the EDS system is responsible for fuel delivery functions why does your car continue to run when the the computer is disconnected?

Do you have a 602/603 engine manual?