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back to my 242 again... 200 1980

posted by  someone claiming to be Anthony on  Sat Nov 25 12:02 CST 2000 [RELATED]

I posted a message before, but have done some more troubledhooting. Get ready this is a long one.

One 1980 242 w/b-21 and k-jetronic. Before replacing head gasket and reconstructing wiring harness, the car would start immediately every time regardless of outside temp. After doing head work and harness, car is difficult to start without messing with things. Here is what I found since the last time.

With the rubber intake bellows off, If I lifted the sensor flap just a hair while my brother cranked, it would start immediately. With the bellows on and not touching the flap, it wont start at all. This is with the cold start injector disconnected, but every one I have seen would start a little hard or at least sputter even without it hooked up. Next, I stood ready with a small battery and alligator clips ready to hook to the cold start injector. With my brother cranking the engine, as soon as I powered the injector the engine would fire. However, even after 20 seconds or more, it would stall as soon as I disconnected the injector. Was the engine running on just the cold start injector? I have checked the fuel control unit and I get a lot of fuel from the injectors by manually lifting the plate and the spray pattern is pretty decent. I only have to lift the plate a little bit and I get fuel. the level varies smoothly as the plate is lifted higher.

Why does the car take so long to activate the airflow sensor? It will run without the cold start injector, but it takes a long time to start. I sure cant jump the injector for half a minute and keep my foot on the pedal.

thanks...







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    Re: back to my 242 again... 200 1980

    posted by  someone claiming to be Don Foster on  Sat Nov 25 14:00 CST 2000 [RELATED]

    "Was the engine running on just the cold start injector?"

    Probably.

    It sounds like a control pressure problem. This could result from something wrong with the control pressure regulator (which DOES have an electrical connection, and thus an opportunity for error). It could also be a misbehaving fuel pressure regulator, which is an integral part of the fuel distributor.

    I'm fighting a similar problem on my '82 (K-jet), and measured the fuel pressure as outlined in the manual. The Volvo manual specifies around 3.3-3.5 bar control pressure, but my car was over 4.2 bar. (Higher control pressure results in a lean mixture.) My engine starts easily when I manually lift the sensor plate, but the engine vacuum is unable to lift it 'cause of the high control pressure.

    The Volvo manual said only two things cause this: A plugged return line (mine is free 'n clear), or a defective pressure regulator. The regulator is only accessible with the fuel distributor out of the car.



    Don Foster (near Cape Cod, MA)







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      Re: back to my 242 again... 200 1980

      posted by  someone claiming to be Anthony on  Sun Nov 26 00:57 CST 2000 [RELATED]

      well, I have verified that the sensor plate is not binding. It moves freely, but I can feel the pressure differential when I try to lift it. I bet I do have a control pressure problem or a plugged return line. Hopefully it is the latter, since I swapped cpr's with no results. I have verified voltage to the cpr, but I do not notice a difference in the way the car runs whether it is connected or not.

      When I lift the plate I feel resistance from the control pressure, but it does require some force to move.

      I have also verified that I have no vacuum leaks.

      Thanks,

      Anthony







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    Re: back to my 242 again... 200 1980

    posted by  someone claiming to be Charlie on  Sat Nov 25 13:19 CST 2000 [RELATED]

    One thing could be that air flow sensor plate is hanging up and that by removing the head and replacing it you some how dislodged the plate on its mount so it is no longer centered. There is a pivot arm and a disc that is held to the arm by a nut. These are really hard to see on B21s. (On a 75 the whole air system is easily accessible being located behind the passenger headlight).

    If the plate gets knocked off center it will hang up on the venturi wall. to fix it you have to loosen the center nut and center the plate. easy to see and fix on a 75 --but not on the B21.

    When you push it by hand is there an resistance????

    The other thing could be that the rubber connector above the sensor plate- between it and the throttle body is not air tight---isn't there an O ring there around the top of air sensor throat sealing the bottom part of that rubber connector to the upper air sensor throat - where that big hose clamp is. If there is not a good seal the vacuum from the intake manifold would be "diluted" and not strong enough to pull up the plate.

    (I know on the '75 set up--the snout bellows ( the one that runs from the air box on the B21)- this had to be solidly connected with no cracks and if it came off or loose the car wouldn't run -because on the 75 set up it was between the manifold - the vacuum source- and the air flow sensor plate.)

    From your last description I'd look for a mechanical reason why the plate is not being raised by the airflow. Either a break in the vaccumm from the manifold to the air sensor plate, Or the plate itself being hung up. Start with verifying a tight seal.






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