SV: Bosch LH-Jet 2 /'84 Volvo troubles

[Stefan Olsson]

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> Från: Michael Skolones <michaels at telerobot.com>
> Till: diy_efi at coulomb.eng.ohio-state.edu
> Ämne: Bosch LH-Jet 2 /'84 Volvo troubles
> Datum:  den 2 september 1997 19:25
> 
>      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


Dear Mr Skolones


The problem You have described is common for the modell i will sugest You
to clean the injectors and check the temperatursensor in the cylinderhead
because this sensor is controling the "warm up" (out of closedloop).


Best Regards
Stefan
18 Years tuning Volvos


www.bsrab.se
stefan.olsson at bsrab.se