function of ignition output transistors

Discussion in 'Electronics' started by mike1875, Apr 11, 2011.

  1. mike1875

    mike1875 Member

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    can anyone pls lemme knw the function of output transistors and secondly what are the signs of a bad fuel actuator in a merc e220 1996??What does an ICV do?whr is it located???Is there any relationship between Coolant temp sensor and bad mileage??The OVP relay...pls mention what happens if it goes wrong??My car shuts up the engine even at 60 mph if the clutch pedal is pressed.....it usually happens on long drives but sometimes in city too....
     
    Last edited: Apr 11, 2011
  2. Ted

    Ted MB Club Veteran

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    An output transistor is basically the last stage of any amplification circuit.
    It is this that connects to the driven device - e.g. loudspeaker, line output transformer (in a crt) or in a car, things like the coils, injectors, pumps, etc. In fact ANYTHING which has electronic control in a car will likely have an output transistor.
    These can operate in a number of modes - current amplification, voltage amplification and iirc, impedence matching.
    The output transistor is 'at the sharp end'. If you have a short circuit, and no form of current limit, it will be the output transistor whice fails.
    Similarly if you have a failure in the control circuitry, - e.g. keeping an output transistor turned on for longer than it should, it will also cause it to fail.
    Output transistors also work harder than any other part of a circuit, this can cause them to be the first part of a circuit that goes intermittent, and eventually fail.

    One thing to note, is that many output transistors which drive inductive circuits (coil/motor/injector etc) are protected by a diode across them. This prevents voltage spikes damaging them. If this diode goes leaky, it will cause the transistor to fail.

    Last of all, if the transistor is wited for current amplification, it is often a 'darlington' transistor. This is effectively two transistors in one, connected as a 'darlington pair' - it's not a special transistor in any way.

    hth.
     
  3. grober

    grober MB Club Veteran

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    There is no fuel accumulator in the E220 setup. It's normally found beside the fuel pump and filter at the rear of the car. Because the injection system operates on a different principle from the older JETRONIC K/KE system its not necessary. note its absence in this picture showing a fuel pump and filter assembly off a E220
     

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    mike1875

    mike1875 Member

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    am not talking abt the acumulator but am talkin about the fuel actuator...as the mechanic said..maybe he meant a faulty throttle body...what generally goes wrong in a throttle body that leads to stalls at high speeds and poor mileage and car not going beyond 4000revs till the second gear??pls help...and there was someone in some other thread who was talking abt some harness switch that tells the throttle plate to open accordingly..wat was he talking abt??pls send pics...and Grober you said....
    "My guess and its only a guess :dk: is your throttle plate position /idle or full load position switch is faulty causing the engine ECU to think the throttle is wide open when it is not or failing to adapt to full engine load. Its a black plastic unit bolted to the side of the throttle plate housing. As KTH286 says clear the fault codes and try again."....pls explain
     
    Last edited: Apr 11, 2011
  5. grober

    grober MB Club Veteran

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    OK here's a photo of the part in question from a cable throttle car. Usually people replace them as a complete unit, but as you can see there is a black plastic housing on the side which can be removed for inspection/repair- altho often this is not possible. The unit contains 2 parts a idle speed control motor and a trottle position sensor +idle/full power switches The replacement cost new from MB for part no A0011410225 is around £590 altho you can pick them up second hand for much less German SPOB: THROTTLE HOUSING MERCEDES BENZ / VDO A0011410225 0001419225 0011410225 A0001419225 A0011410225
     
    Last edited: Apr 25, 2011
  6. grober

    grober MB Club Veteran

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    As far as I am aware in these ECUs the true function of the "output transistors" which is unfortunately a misleading name :doh: is to act essentially as a switch to ground . The ignition coils are constantly fed with 12v via the ignition supply and are then " momentarily grounded " by the ECU when its digital circuitry has decided from all its input sensor data the appropriate moment to switch the transistor-- this stops flow in the coil primary [low voltage] causing its field to collapse inducing a current in the secondary coil [ HT CIRCUIT]which fires the 2 spark plugs in the "lost spark" system. :dk:
    Don't know if I have explained that very well so anyone wants to jump in and explain it more clearly be my guest.;)
     
    Last edited: Apr 11, 2011
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  7. Ted

    Ted MB Club Veteran

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    Yes, but the term output (or perhaps driver) transistor is still correct.
    It's operating in saturation, in sink rather than source mode.

    Basically, as you say, a very fast switch.
     
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  8. camerafodder

    camerafodder Hardcore MB Enthusiast

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    Ted does think make you our 'Tranny man'? :p
     
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    mike1875

    mike1875 Member

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    hey grober...wat can possibly b wrong wid my car's throttle assembly...mine one is a cable throttle system....the one u showed me in the pic...and how do we repair the respective faults??today,i cleaned the little electric contact underneath the housing..the little thing was being pressed by the throttle butterfly...i hope i name it correctly...i cleaned the contact..the other side too that..that was hanging out of the butterfly...but the car again stalls...but as usually quite less often...but the problem gets solved if i turn off the ignition and start up again,but for a while only....and further whats the sensor attached to the air filter housing right before being connected to the throttle body..its a little black thing with minute wires(2) and a little bubble kinda thing at the top?is it the oxygen sensor(am not talkin abt the MAF thing..m talking abt the sensor which comes rt b4 the connection of the air filter hose pipe to the throttle housing)....do u think the main culprit for a poor mileage,car stalling as well as not going beyond 4000revs till the second gear is one n the same??if not..what are the possibilities???car goes like a bullet upto 4000 revs...but the main issue rt nw is the thirsty car which is a serious drunkard....m outta of my senses..pls help...n can u pls send me some more pics of the throttle housing from all the angles as i cant see any wire attached to it except the one underneath it which goes into the backside of the black thing(there r two wires rt outta that switch pressed by the butterfly)..i've seen the pics on ebay..with a wire hanging out and a coupler thing at the other side..but i cudnt find any on mine..although i chkd the model no thoroughly...
     
    Last edited: Apr 12, 2011
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    mike1875

    mike1875 Member

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    theres a correction...i was wrng,theres a wire going out underneath the blk plastic thing which is further attached to a coupler located rt under the exhaust manifold...advancing to the ECU....
     
  11. grober

    grober MB Club Veteran

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    The small black sensor before the throttle body is the intake air temperature sensor [ thermistor bead type I think] which tells the engine ECU what the inlet air temp is. It does not have a major effect on fuelling and the car should run well without it in the absence of air leaks. If I recall correctly the idle speed control is " adaptive"-- that is---- over a series of short journeys the ECU should learn the limit and extent of the throttle travel. Now you have cleaned the contacts try driving the car for about 10 short journeys lasting long enough for the engine to get warmed up and then cooled down and see if the idle settles down.
     
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    mike1875

    mike1875 Member

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    wat do u mean by to see if the idle settles down??idling is usually ok wid my car...on a warm up drive like u said....the car runs alrt for a while but a pep or two the car sometimes starts stalling...pls elaborate...and further...i observed the butterfly thing on the throttle housing...it has a hook type springed thing in the middle of the main bracket,at a slight difference to the main bracket that is pulled by the cable,that hook type thing moves up n down automatically and a change in the idling can be observed...whats that hook type thing?what does it do exactly??it moves on its own...is it electrically controlled???the other day i got my ecu exchanged wid some other 220...but the prob persisted...theres only one fuse in the OVP..which means that the fuse was replaced...can it b a cause to stalls and poor fuel eco??the mechanic told my throttle housing is faulty but he said that without even looking thoroughly..dunno how he reached to that conclusion!!!The cable harness seemed to b ok..cause i opened up that black housing which contains the engine harness and all sounded quite well....i m asking once again,wats exactly wrong whn we say that the fuel actuator or throttle housing is at fault???my MAF too got broken..oops...but even after exchanging it with a healthy car for a while..the stalls and poor eco continued...so basically my main problems are stalls and poor eco...the misfire thing was due to a faulty fuel pump or pressure regulator which i've got changed and so was the fuel filter at the rear....but i think it has nothing to do wid my probs of stalls etc...the other day car was started up by the mechanic after removing the plugs cover...as the engine was still running..he pulled out the HT leads connected to the spark plugs...no.1 and 3 were sparking like hell..but no2 and 4 were sounding asleep..cud that too be a prob..but the mechanic didnt focus much on that..i mention once again that car goes like fire upto 4000revs...runs well but city drivin is **** like...
     
  13. grober

    grober MB Club Veteran

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    These cars are known for having problems with the ignition coils failing as they heat up. Maybe this is what's happening- one of the coils is failing after it heats up. The lever you refer to is probably the idle speed actuator moving [electrically]to control the throttle plate position. In the end its almost impossible to diagnose a multi faceted problem like this at a distance- get the car to a mercedes specialist who is experienced in the ignition and fuel systems of this model.
     
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    mike1875

    mike1875 Member

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    thanx for that grober...but will u b kind enough to lemme knw what are the things to be focused on generally...for such probs???i knw that can b annoying but me too am helpless cause all the workshops over here have monkeys and donkeys appointed..moreover the Merc dealership here in my city went bankrupt due to a fraud of abt 10 s500's bookin wid advance payment and not delivering the cars...i mean if u cud pls tell me abt the possibility of a bad eco and car not going beyond 4000 revs...stalls can b due to the coils and i'll get em checked...that day i got my car scanned with a Launch scanner...it nvr mentioned any coil prob..he connected the leads into the connector no1,8 and 16..hope it was rt...but whn he was clickin on the ecu etc option on the scanner,it couldnt be synced...all it told was...idle regulation at high,idle regulation at low,faulty TPM and EFS....
     
    Last edited: Apr 12, 2011
  15. grober

    grober MB Club Veteran

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    First are you testing the engine revs with the car stationary- There is safety feature which stops the engine over-revving when stationary.
    It might be worth trying to source a second hand throttle assembly since that seems to be what your mechanic is homing in on.

    What is causing your high fuel consumption? Could be many things. The engine fuelling is controlled by many sensor inputs to the engine ECU. It could be any of these really. Common failures are the MAF or the lambda sensor or possibly the engine coolant temperature sensor.
    An engine that is not generating its full power will use more fuel as you need to use more throttle to get the car moving. Power drop can be due to lack of fuel [ choked fuel filter] faulty ignition -usually the HIGH TENSION SIDE or ironically a weak mixture due to inlet air leaks. Other strange problem is a partly collapsed/blocked catalytic converter.
    Non engine faults means power is lost in the transmission which can be a slipping torque converter, autogearbox or binding brakes.

    You just have to work your way through the possibilities until you find the problem.
     
    Last edited: Apr 12, 2011
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    mike1875

    mike1875 Member

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    i'll do that...i'll get the engine coolant sensor also checked...whr is it located in my 220??and m testing the car on the go n not while stationary....m already arranging for the throttle assembly...got the fuel filter changed recently.may be 20 days ago..it wasnt choked but had too much of dirt n grime...pls explain how do i check the catalytic thing??
     
    Last edited: Apr 13, 2011
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    mike1875

    mike1875 Member

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    how do i chk the ctalytic convertor??what happens whn theres a faulty coolant temp sensor...
     
  18. grober

    grober MB Club Veteran

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    This details tests for a clogged catalytic converter. you could use the lambda port on the exhaust manifold as its easily accessible? All Catalytic Converters - How do I know if my catalytic converter is defective?
    The engine coolant temperature sensor is located on the front coolant manifold under the black front engine cover . Don't confuse the temperature gauge readout sensor with the temperature sensor for the injection system. sensor/switch 1 may well be missing
     

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    mike1875

    mike1875 Member

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    can u pls elaborate the location as well as the checkin methods...whn i took off the black engine cover at the front with the merc's star on it..to specify...i found a connection thing leading to the aux fan...just to mention...i hope m lookin at the rt place...can u put on a real pick n mark the locations...?I'll b vry thankful you....n pls define the MAF,lambda sensor as well as the oxygen sensors and their respective locations..they sound one and the same to me..
     
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    mike1875

    mike1875 Member

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    .i jus found on the net...does 220 have two lambda sensors??one before the CAT and the other one after that???
     

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