John ,this is an interesting one. My 89 Plus Four also has an Omex 710 ecu. Sometimes it churns quite a while before starting but other time starts straight away . May I ask how you start it? The form is, turn on ignition, wait until the fuel pump primes -you will hear a swish and then a audible click -then turn the key or press the start button. Do not touch the accelerater until the engine runs.
