Where is the ECU on a 1981 308 GTBi? | FerrariChat

Where is the ECU on a 1981 308 GTBi?

Discussion in 'Technical Q&A' started by Trent, Dec 10, 2003.

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  1. Trent

    Trent Formula 3

    Dec 10, 2003
    Indialantic, FL
    Full Name:
    I have been looking and cant seem to locate the ECUs on my 1981 308 GTBi. My rear bank of cylinders will stop firing for long peroids of time causeing the cats to get RED hot, etc. I checked the output from the timing test point in the engine bay and the two flywheel sensors have a steady 29Hz signal, but only the Front Coil is getting a timing signal.

    Q1: Where are the ECUs? I have looked for >10HRS [Maybe I am blind]

    Q2: Do I replace/repair with
    a. OEM Part
    b. Fiat Part (Cross Ref Number?)
    c. Crane Ignition System

    Thanks for the help

    My Ferrari is at http://www.TrentCarter.com
  2. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    The Marelli Digiplex boxes on my 83' QV are on the drivers side in the trunk under the carpet. Unbolt the try and out both of them come. I assume this is what you are talking about. It doesn't have an ECU for the CIS Fuel Injection.
  3. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    Groton, MA
    Full Name:
    Verell Boaen
    More specificly, they're in the very bottom of the rear quarter panel well behind the rear driver's side wheel. Lift the carpet & remove the cover plate that's in the very left of the luggage compartment.

    BTW, down at the bottom of the well is a rubber plug with a drain hose in it. It's very common for the hose to get plugged up & the well to be 1/2 full of rusty water. I've even heard of the ECUs being nearly submerged. What a miserable place to put electronics 8{...
  4. Darolls

    Darolls F1 Veteran

    Jul 2, 2003
    Full Name:
    Also, a good idea is to put silicone grease over the wires at the connectors, and some additional in the boot covering the connectors.

    Moisture infiltration is a common problem.
  5. Trinacria

    Trinacria Formula Junior

    Aug 7, 2002
    Long Island, NY
    Full Name:
    Baldassare Guzzo
    Don't jump to conclusions about replacing them. Check the vacum hoses for good connections and check the connectors for good connections. Also, One of the bolts is used as a ground with three ground wires going to it. Take off the bolt, clean the crap out of the area and the ring connector with a wire brush and put it back nice and tight. Also, you can switch the plugs on the boxes to see if the other bank experiences the same problem. Lastly, check the connecctions on the coils. A bad coil connection will do the same thing.
  6. Trent

    Trent Formula 3

    Dec 10, 2003
    Indialantic, FL
    Full Name:
    Well the problem is fixed. It was a cold solder joint on one of the digiplex units.

    Symptom: Wiggling the wiring harness molex would enable/disable the rear cylinder bank. I switched molexes from one digiplex to the other and the problem stayed with one digibox, thus the problem was internal to the box, not in the molex or wiring.

    I opened the box and found a cold solder joint on the two 12v pins to where they connect to the Circuit board inside. I resoldered it and it works perfect.

    Thanks for all of the help!

    Finding the darn digiplex box location was 90% of the effort.

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