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  #1  
Old 08-25-2004, 06:03 PM
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Exclamation Reset Computer on 602???

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???)
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Old 08-26-2004, 08:21 AM
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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.
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Old 08-26-2004, 12:29 PM
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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-
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Old 08-26-2004, 02:22 PM
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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
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Old 08-26-2004, 03:27 PM
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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.

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Old 08-26-2004, 05:20 PM
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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.
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Old 08-26-2004, 08:09 PM
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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?
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Old 08-27-2004, 12:07 AM
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Thanks all for the advice!!
I am going to try the re-set in the AM.
If I do need an EDS I will be in contact w/ you, Grdenko!
Tim: I do have the manuals, but I haven't delved into them deep enough yet to totally explain the function the EDS has over the IP. All I can positively confirm is that some signal is being sent from the EDS to the IP to restrict fuel, because w/ those two connectors on it is cutting out fuel @ 2k rpms and w/ them off it is not.
If nothing else works Ihave a buddy at the Stealership who can run some more diagnostics, if I can get the damn thing flatbeded the 75mi up there.
Thanks and keep y'all updated.
-M-
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Old 08-27-2004, 12:22 AM
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At the moment, I'm with Tim - there is no electronic modification of *fuel delivery*, however there is electronic control of the wastegate, EGR, and idle speed - but I think that's it. The 602/603 engine manual has some GREAT information in there, but you need to read it, which can be time consuming..

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Old 08-27-2004, 07:35 AM
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The 602/603 engine manual is, by far, the best MB manual I've ever purchased. It contains extensive diagnostic procedures and also has quite a bit of information about how the Diesel injection system and the EDS work.

The boost control system in this car is very nice when it is working correctly - one of the components in the system is an intake manifold flap that will actually restrict air into the manifold, I believe this flap is closed by the ECU to build boost quickly and then opened to dump the boost into the intake manifold. I verified this my monitoring the current draw thru the vaccum control transducers while driving the car. If your ECU is not working correctly maybe it is holding this intake flap valve closed and your car is being starved for air. The default position of this flap is open - so unless you observe the valve with the car in operation you might not know its being closed. BTW if the flap were being closed at the wrong time you would see vacuum in the intake manifold - sound famaliar?

The procedure for reseting the codes outlined by Grdenko is to be used to inform the computer system that you have corrected the problem that is indicated by the presence of the particular error code and you want to clear the code from memory - it is not a "general CPU" reset procedure. I'm amazed that you would want to erase the error codes without knowing what the error codes were trying to tell you.

You REALLY should spend some time reading the 602/603 manual - it contains the exact information you need to fix your car in a fairly digestable format.
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