740 Air Mass Meter problems

Discussion in 'Volvo 740' started by Ron, Jul 15, 2003.

  1. Ron

    Ron Guest

    I recently had my 89 740 8V non turbo serviced, i.e. (tune up) at that

    time my mechanic informed me that the AMM was bad in my car because i
    was having a hard time getting the thing to start and when it would
    start it would die so the starting process could take 2-4 minutes for it

    finally to start and stay running ( hot or cold weather usually first
    start of day or after sitting for 3 or 4 hr.). He checked the fuel
    check valve it was fine, but he found that if you disconnected the AMM
    it would fire right up then let it idle for around 30 seconds and replug

    in the AMM it would continue to idle and warm to running temp then it
    was fine to drive. It does however tend to hesitate from a stop when
    taking off (almost like bogging down like a old carburetor. car with a
    large fuel dump). then accelerate fine.

    I bought this car 5 months and has always started hard it is the same as

    when I bought it. A couple of days ago my son tried to start the car
    without doing the AMM trick it started and died a couple times then
    nothing for days would only crank not start AMM plugged in or not. I
    checked and replaced the fuel relay, replaced a bad fuel pump fuse.
    Confirmed that the tank pump worked and the main fuel pump worked.
    Confirmed fuel to the fuel injector bar, took spare plug using #1 wire
    confirmed by holding threads next to the block I had spark (spark seemed

    small to me I no sure how intense it is to be but it did spark across
    the plug gap). Still no start. Then I pulled the radio suppresser
    relay on the water res. tank and reseated the connector I also unplugged

    and reseated the RPM sensor a couple times, and tightened up the power
    booster thing on the driver side inner fender wall ( it only has one
    screw in it attaching it to the wall I need to find another) Unplugged
    the AMM Bingo it started. Still hesitates slightly when
    accelerating from a standing stop even when warm. I hesitant to drive
    it because I not confident in its ability to routinely restart.

    New Parts:
    Alternator, timing belt, Fuel pump relay, engine block heat sensor,
    plugs, RPM sensor papers to be replaced clean cable white band I did
    not replace it in must have been replaced by privies owner. Idle control

    value works and has been cleaned, throttle body cleaned, flame trap new.

    Question :
    Is the AMM bad? And if the AMM was bad wouldn't run like crap with the
    thing plugged in not just have a starting problem?
    If the AMM is not bad what's going on?


    Ron, Jul 15, 2003
  2. Ron

    Tom Corelis Guest

    If the AMM is bad you should be able to unplug it and it will start up
    and run although it will be in "limp home" mode. It will be difficult
    to accelerate without killing the engine.

    Other possibilities - fuse #11 15 amp pre-pump
    You can test the AMM with a digital volt ohmmeter; not sure of values
    since my book only goes up to 88.
    When was fuel filter last changed? There may an additional fuel filter
    (screen) in the gas tank - not sure on your year and model.
    What is the state of vacuum lines? Leaks can contribute to
    driveability problems. Old fuel injector seals can aggravate vacuum
    leaks and make them difficult to diagnose.

    You said the car had a 'tune up'. Was this done by a Volvo shop or
    some other shop such as a tune and lube? Did they change the air
    filter and fuel filter also? If you don't have one already find a good
    Volvo repair shop. I have found that many non Volvo shops are
    befuddled by Volvo FI and what it needs to run right. Even though I
    like to work on my Volvo, I have two or three Volvo shops nearby that
    I can turn to if I'm stuck or if I don't have the time or desire to
    tackle a difficult job.

    I also keep a 'spare' AMM around. I was able to pick one up at a
    local Pic-A-Part wrecking yard for $28. Make sure it has the same
    Bosch number as yours. Later B230 turbos and non turbos use the same
    AMM (007 -last three numbers).

    Also, for more help try the Swedish Bricks message board. There are a
    lot of good folks on that board with a lot more experience than me.
    Good luck.

    Tom Corelis
    88 760T
    87 240DL
    71 142S
    Tom Corelis, Jul 19, 2003
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