Bosch LH-Jet 2 /'84 Volvo troubles

[Michael Skolones]

     Help!
     
     Does anyone out there know what the LH-Jet 2 test port signal means 
     _before_ the 02 sensor kicks in and closed-loop mode begins?
     
     Here's my problem; I don't think it's all that uncommon on LH-Jet 2 
     Volvos.  Once the car reaches closed-loop mode, it runs fine.  When 
     first starting the car in the morning (about 60 deg F outside), the 
     car will fire right up, run for about 30 seconds (or less) and quit as 
     if all fuel were cut off, and is very difficult to start thereafter.  
     I'm attempting to diagnose the problem using the LH-Jet 2 test port 
     (located near the ignition coil and air mass meter on my 240 Volvo).  
     
     When the car is warm and closed-loop mode is functioning properly, the 
     signal at the test port is a time-varying voltage related to the 
     signal produced by the O2 sensor.  The air-mass-meter mixture screw 
     can be set so that the test point voltage bounces back and forth 
     regularly between approx 0 volts and approx 4 volts.  
     
     When the car is cold, the test port signal behaves differently.  When 
     the car is first cranked, the signal pops up to the "high" value ( 
     approx 4 volts as in closed loop mode) and remains there until the car 
     starts.  After 15-30 seconds the signal falls back to zero; within 
     five seconds the car will stall.  The car seems to restart only when 
     the signal pops back up to "high", which for some reason does not 
     happen every time the motor is cranked.  
     
     I just installed new plugs, plug wires, cap, rotor, air filter 
     thermostat, timing belt, etc.  I'm about to change the fuel pump 
     relays.  The air mass meter isn't very old, though this doesn't 
     necessarily mean anything.  Since the car runs great once it starts, I 
     don't think the air mass meter is at fault.
     
     
     As a second question, does anyone know how to test the air mass meter, 
     other than the classic "unplug it" strategy?  
     
     Third, would a faulty block temperature sensor prevent the car from 
     running?  
     
     Thanks
     
     Mike Skolones