FAQs about Fuel Injector Air Mass Meter.

  • Various ways to obtain an air meter.
  • Simplified desciption and ascii art of an air meter.
  • Fuel Injector summary.
  • How does an air mass meter operate?

  • Various ways to obtain an air meter.

    Date: Tue, 16 Feb 1993 16:01 EST
    From: Jim Greenberg <JAG2@vms.cis.pitt.edu>
    Subject: Re: help! mass sensor
    To: J019800@lmsc5.is.lmsc.lockheed.com

    Cc: swedishbricks@me.rochester.edu

    DLowe_ I had to replace the air mass meter twice in two years. The car is an '83245A which now has about 86,000 mi. The dealer charged me $550 the first time; the second time I ordered one from RPR in Berkeley for $389 and changed it myself. The second time I also changed the thermostat that controls the door from the warm air return tube to the air intake/filter housing. I doubt that there is any way to circumvent this expensive but necessary repair. - Jim

    From: alfred@nyquist.bellcore.com (Alfred Kwan 21342)
    Subject: Re: help! mass sensor
    To: fsf@wv.mentorg.com (Rick Farnbach)
    Date: Tue, 16 Feb 1993 16:35:31 -0500 (EST)
    Cc: swedishbricks@me.rochester.edu

    I bought an air mass meter from a local junk yard for $100 for my 745T. I think there are two different types; the early 240 has an aluminum body and the later one has the black plastic body. The black plastic one on my 745T is the same AMM as the one on the non-turbo 740s and I think the later 240s use the same AMM. You might want to call a few junk yards and check for 240s and 740s AMM. Do copy down the Bosch number so you can verify the correct number over the phone.

    Good Luck


    From: Mark Nathanson <nathanso@umdnj.edu>
    Subject: Re: help! mass sensor
    To: J019800@lmsc5.is.lmsc.lockheed.com
    Date: Tue, 16 Feb 93 16:34:09 EST
    Cc: swedishbricks@me.rochester.edu

    > PROFS Nickname: DLOWE
    > i own a 1985 245dl. the engine will start, but will only run for 3 to 4
    > secondsbefore dieing. if i unplug the mass sensor the engine will
    > continue to run. however you cannot drive the car due to lack of power.
    > the cost of a new mass sensor is $300. any help would be appreciated.
    > CDL

    I recently purchased an air mass meter for $95.00 used. The yard was: Webers at 215-267-4400. They said that they took it from a car that was running and guaranteed it for 30 days. It has been running fine for many months.

    There are two tests of the air mass meter that you can do with a VOM. I can't recall them offhand but will check on them tonight. I checked my old AMM with the VOM and these tests were OK!!! Does anyone know if the AMM is really bad or was the agency that diagnosed the problem REALLY BAD?

    Date: 17 Feb 1993 09:48:56 -0500 (EST)
    From: V093P9MD@ubvmsb.cc.buffalo.edu
    Subject: Re: air mass meter
    To: swedishbricks@me.rochester.edu

    Check around for prices. I paid about $240 (returned core) new. It's extreamlty easy to replace. If you can handle a screw driver and a socket wrench you can do it in not much more than 15 minutes. BTW the reason for the terrible power when you disconnect the air mass meter is hat it goes into an emergency get home more. It injects the fuel at a steady rate, since it isn't able to compensate an changing parameters. It's default it to make shure the car doesn't stall out the whole time, resulting in an OK idle, but lousy acceleration.


    Date: Thu, 26 Mar 1992 09:19:51 -0800
    From: "Y. Alan Wang" <wyl@nsd.3com.com>
    To: senator@cco.caltech.edu, volvo-net@me.rochester.edu
    Subject: Re: Air Mass Meter

    My 84 shared the same failure at 73k miles. I could start the car but it would not be idle but quit. It was an expensive job, the Air Mass Meter is the brain of the fuel injection, parts, one hour installation and one hour diagnostics. I really think Volvo's parts quality is not up to par.


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    Simplified desciption and ascii art of an air meter.

    From: martenbf@mentor.cc.purdue.edu (Brian F. Marten)
    Subject: Re: Air Mass Meters
    To: volvo-net@me.rochester.edu (Volvo Net)
    Date: Fri, 27 Mar 92 9:03:20 EST

    There is a trap door in that mass above your air-filter. The more air that is sucked past the door the more the door is opened. This is measured in some manner and used to control the Fuel metering system.

                       _______________________  mmmmmmmmmmmm
                      /     ------>           booo
                     /     ^ ------>
                     |      |^ ------>                hose
                     |      ||^ ----->_________pooo
                     |\  air|||flow /|       |   wwwwwwwwwwww
                     | \___________/ |___ ___|
                     |       I       |__|^|__|
                     |    ^  I_______o___|   |Air/Fuel Meter Housing
                     |    |          |       |_______________________
                     |    |      ^       ^   |Air Filter Housing    |
                          |      |   ^   |                          |
                          |      |   |   |__  Fuel Flow Needle & Orifice
                          |      |   |______  Pivot Point
                          |      |__________  Swing arm
                          |_________________  Trap Door

    At least this is how it works on my GLT.

    This is over simplified. There are more needle valves, most of them are regulator valves of some sort or another. Mine has like 7 or 8 and they are all rather expensive. So I hope that by putting Techron in the tank every now and then I can keep them from gundging up for a while longer.

    The SAAB's use a Pt air mass meter. Which actually detects the air mass, not just the volume. Based on Heat Loss Coefficients I think. Any one care to correct me on this one?

    Wow! What a Concept! -- Wembley Fraggle.

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    Fuel Injector Summary.

    Date: Fri, 27 Mar 92 10:38:30 EST
    From: wiegman (Herman L. N. Wiegman)
    To: E_POZZI@acc.haverford.edu, martenbf@mentor.cc.purdue.edu,

    Subject: Fuel Inj Summary

    hey netters,

    the volume has been out of this world, but most of it is lagit! Must be a bad month for volvo's out there...

    Back to business....

    Bosch has offered many FI systems. The systems operate off one of three measurments, manifold pressure, manifold air flow, or manifold air mass. Other methods exist, but they are not as well used.

    1971-73 D-jetronic Manifold pressure also temp comp.
    1974-79 K-jetronic Air flow sensor damper plate arm
    1979-85 K-jet w/ Lambda Air flow sensor used on 760's too
    1983- LH-jetronic Air Mass meter B23/B230/new Turbos

    There is also LH-2 which is still based on an Air Mass Meter..

    How 'bout that ASCII drawing by Brian! wow.. major Air Flow Sensor!

    all the best,


    Herman L.N. Wiegman -> wiegman@orion.crd.ge.com
    General Electric - Corporate Research & Development
    - the Flying Dutchman in the DSP swedish brick -

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    How does an air mass meter operate?

    Date: Tue, 29 Jun 93 09:49:01 EDT
    From: wiegman@orion (Herman L. N. Wiegman)
    To: swedishbricks@me.rochester.edu, ron@drd.com
    Subject: Re: Air-Mass Meter question?

    Ron & Netters, [ LH-jetronic car owners.. '83+, 240/700/900/800?]

    The Air Mass Meter (AMM) is a sometimes troublesome, and exspensive, device on newer Volvos. It is the essential measuring device for the LH fuel injected cars. It is a squarish box in line w/ the air filter assembly and the intake manifold.

    The principle of operation is based on heat transfer from two "hot-wires" to one sensor wire. There is an internal electrical circuit, a Wheatstone Bridge, which helps to accurately measure the resistance of the sense wire. (It is a Neg. Temp. Coefficient pick-up wire.)

    These "hot-wires" are sometimes fail due to impurities in the air and shock (road traps). To keep them clean, the hot-wires are "burned" after turn-off of the car. 12 volts are applied for 2~3 seconds. The two wires should glow and then cool off. If this does not happen, either the electronics are bad (doubtful) or the hot wires are faulty (more probable).

    >My mechanic has informed me that my Air-Mass Meter needs to be replaced.

    Warning: I personally think that 1/2 of the "repairs" done to Volvos with "bad" AMM are not warrented. If you Volvo is running like dog-poo and you have no power past 2000 rpm, then consider the advise worthy. If not, walk away with your wallet.. quickly. Mechanics earn a small profit on parts that they install.. an AMM is worth ~$120 in instant profit.

    To test the AMM yourself... [ from Jawa ~jtembulk@spica.cv.com]

    >* Air Mass Meter checks out at OK
    > Based on multitester reading of 3.5 ohms [ valid range 3.5 to 4 ohms ]

    I am not sure which leads this measurement is taken, but I think that it tests the ambient resistance of the sense wire. The hot wires can be checked with the above mentioned "burn-off" test at turn-off of the Volvo.

    Check and clean all connections as well..

    best of luck,


    Herman L.N. Wiegman -> wiegman@orion.crd.ge.com
    General Electric - Corporate R&D, Schenectady NY
    - the Flying Dutchman in the DSP Swedish Brick -

    Date: Wed, 30 Jun 1993 17:42 EST
    From: Jim Greenberg <JAG2@vms.cis.pitt.edu>
    Subject: Re: Air-Mass Meter question?
    To: ron@drd.com
    Cc: swedishbricks@me.rochester.edu

    R - My '83 245 has needed 2 air mass meters replaced! I think the 2nd one was needed (2 yrs after the 1st, and only about 5,000 mi later) because the thermo-stat that control the warm air return to the air filter/air intake was not replaced the first time. So replace this at the same time (I think too much hot air killed the air mass meter). I don't usually work on my cars but when I heard that the air mass meter needed to be replaced again (Volvo dealer parts and labor was almost $600), I ordered one for $385 from RPR in Berkeley and put it in without any trouble. The thermostat was harder to change. The guy at RPR told me that the air mass meter was built by Bosch and that these units were often rebuilt ones (you send them the old one when you take it out); same price,however.

    -- Jim

    From: Dave Munroe <dmunroe@hpvclmun.vcd.hp.com>
    Subject: Re: Air-Mass Meter question?
    To: swedishbricks@me.rochester.edu
    Date: Wed, 30 Jun 93 15:52:22 PDT

    Jim writes:

    > R - My '83 245 has needed 2 air mass meters replaced!

    They are expensive. Shortly after I had mine replaced, the mechanics at the dealership discovered that the aftermarket ARA A/C compressor (put on by the original owner) was whacking the air mass meter whenever the engine was revved, because of the tight fit.

    '85 244 DL 122k

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