911 Motronic repair



Introduction

911, 3.2 Carrera, model '84 - '89 have all a Motronic Fuel Injection system. This motronic system is also called a pulsed injection system. That means the system only sprays fuel into the intake manifold when it is required in the combustion cycle. When you use this method, it results in more accurate control of fuel levels and delivery but also maintain ideal stoichiometric air/fuel ratio.

Failures

In general the Motronic Fuel Injection is very reliable. Problems arise when the connected sensors are not functioning properly. But sometimes the Motronic computer is the trouble maker. Bosch is not producing these Motronics anymore, so new ones are virtually impossible to get or you have to pay a lot of money. Sometimes the relay of the system fails. That is the reason why most 911 drivers have a spare relay in the car. The relay (position close to motronic beneath driver seat) is in fact a double relay: one to control the Motronic and one to control the fuel pump. Anyhow if the user checked the relay and sensors and the car has still problems: We can effectively repair the defective controller for you and restore it to specs !


Common symptoms of a failing Motronic 3.2 are:

  • Engine will not run at all (no start).
  • Bad idle running (fluctuating or > 1000 rpm).
  • Fuel consumption too high.
  • Burning smell in your car (overvoltage).


  • Removing the Motronic from the 911

    First disconnect the car battery before removing the motronic. Ensure the battery earth cannot be accidentally reconnected until you are ready to do so. The motronic system is located beneath the drivers seat. It is not necessary to remove the seat but move the seat all to the back. Further lift back the carpeting and there you see a bundle of cables and the motronic unit. The motronic is connected to the bottom plate with 4 nuts. Release these 4 nuts. Release also the cable and unbolt the relay to make it easier to remove the motronic. Finally the unit is released from the car.



    Motronic 3.2 Carrera.



    Motronic 3.2 Carrera 35 pins connector.

    The Porsche part numbers are on the top cover of the unit. The above unit is a unit with Porsche number 911 618 111 12 and a Bosch part number of 0261 200 078. The Porsche part numbers for the Motronic and corresponding Bosch part numbers are listed up in the table below.

    911 3.2 model Porsche part number Bosch part number
    '84-'89 911 618 111 xx 0261 200 050
    '84-'89 911 618 111 xx 0261 200 051
    '84-'89 911 618 111 xx 0261 200 078
    '84-'89 911 618 111 xx 0261 200 082
    '84-'89 911 618 111 xx 0261 200 085


    Overvoltage

    Overvoltaging of automotive electronics can result from an overcharging alternator or a high capacity battery charger. In most cases the damage is catastrophic to the units. Overcharging alternators are difficult to avoid. Once an overcharging condition is discovered, e.g. buzzers going off, bright headlights or eradicate tachs, the alternator or the regulator should be replaced. This happen with your Motronic when you have an overvoltage problem:



    Broken Motronic due to overvoltage.

    And this broken unit you will smell in your car. But if you get your Motronic back from repair service, please first fix your overvoltage problem first !! 928-ECU-repair managed to repair this unit. Below you see a replacement unit (prototype) for the burned 0127 Injector chip inside the motronic.



    Prototype of 0127 fix.

    Repair-service

    928-ecu-repair offers you a repair of the Motronic for a reasonable price. Due to the large number of variants of the basic unit, it is often not possible to offer an exchange unit from stock. Your faulty unit can usually be turned around by our workshop in 3 working days.

    Once you disconnect the faulty Motronic from your car, send the unit to 928-ecu-repair. When we receive the Motronic, the first thing we do is connect the unit on a Motronic-testbench. This PC controlled testbench acts like a 911 car and with a logic analyser we measure the signals of your faulty Motronic. Next step is replacing of broken parts and retest again.

    Warrant and prices

    We offer a 2 year warranty on replaced parts and labor. Any obvious abuse of the unit will render the warranty invalid. Modifications to the car's systems are beyond our control, and are at owners' risk. Please email us for a quotation for your Motronic repair. Our preferred payment method is bank transfer (or Paypal for our international clients).


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