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Cold Start Valve (CSV)

Discussion in 'Mondial' started by dfranzen, Oct 22, 2014.

  1. dfranzen

    dfranzen Formula 3
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    Aug 31, 2013
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    Chasing down starting issue

    Up until month ago car started first turn cold or hot performed this way for past year of ownership

    then last month sometimes cold but hot took a few turns and hold pedal halfway-had a bad accumulator

    replaced accumulator

    Now
    sometimes cold start on first try

    hot still requires holding pedal down

    had mech check it out :
    pressure stays in manifold by checking/pushing the "intake plenum"
    was told 02 sensor is no good, does not change idle if disconnected while running
    placing a test lamp in CSV harness does not register voltage
    was told maybe thermatine switch
    checked resistance thermatine valve and it reads 0 cold and about 120ohms hot

    read something about a resistor or diode in the therrmatine harness

    where is this resistor or diode?


    also had weird thing happen last week car just died while running at speed and wouldnt turn over until 15 minutes or so no matter how much gas pedal then finally started

    after got home checked fuse box big connector looks ok , fuel pump relays relays felt little loose so pulled out cleaned and put back in

    back to sometime start cold and push pedal when hot start

    any ideas where to look next?

    replace relays?
     
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  3. srephwed

    srephwed F1 Rookie
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    for such a simple system they sure can drive you crazy sometimes.this may not be any help but here goes. in stumbling through my starting issues I learned a couple of things.the cold start system which can flood the system can be easily disabled by disconnecting the connector at the plenum. The accumulator is a very important part of the system. Also you have two fuel pump relays, a start and run. My particular trouble wound up being the run relay because it would start,then stop and after a couple of tries would stay running. What seems to be the hardest to determine is if you are flooded or have lost fuel. you must crank and crank for both problems. Also there is a check valve at the fuel pump to keep fuel primed. Hope this helps you. have fun and good luck
     
  4. mulo rampante

    mulo rampante Formula Junior
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    As Fred mentioned, there's an anti-drainback valve located in, or just after, the fuel pump (depending on year). This valve, along with the accumulator serves to keep the system pressurized for some time after the fuel pump is shut off. Together these parts guarantee fast delivery of fuel, and more importantly perhaps, prevent a vapour lock condition.

    If this valve fails 'open' or partially closed (e.g. due to debris) the symptoms are exactly like an accumulator with a perforated diaphragm.

    There's a spec for pressure vs. time after fuel pump shutoff either in the service manual or one of the various Bosch manuals.

    I would look at this next. I think it is a more common problem than people seem to realize.
     
  5. Rifledriver

    Rifledriver Two Time F1 World Champ

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    That will not cause it to just die at speed.

    I would test the 3 crank sensors. They are a winding so with vibration or changes in temp they can go to an open circuit then close again.

    I am afraid a proper test requires removing them, attaching a VOM and gently banging them on something that is not steel.
     
  6. mulo rampante

    mulo rampante Formula Junior
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    Sorry, I was speaking specifically to the hot start issue.
     
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  8. srephwed

    srephwed F1 Rookie
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    As rifledriver said there are three sensors on the flywheel. Right bank,left bank and tach. I also had trouble with this. My tach sensor went bad and while driving it seemed as if a monkey was turning my ignition off and on. I noticed the tach would zero then bounce back up when this occurred. I replaced all three while doing the job. Started it up after repair and I had a four cylinder. Found one of the pins had pushed back in the connector.Point is if tach sensor is bad engine will not run,if other sensor is bad you have half an engine. hope this helps
     
  9. Rifledriver

    Rifledriver Two Time F1 World Champ

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    It is a "Tachometric" sensor. It means RPM. It is not for the "tach".
     
  10. dfranzen

    dfranzen Formula 3
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    hummm that makes sense road was a little bumpy when it went died and when it cooled off it worked again (had similar crank sensor issue with my benz)

    VOM = voltmeter? and what voltage would I expect?

    Does this require removal of tranny?
     
  11. dfranzen

    dfranzen Formula 3
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    think I located two of them seems there are 3 on a 3.2
    is this the test to perform?
    found this link :
    "The crank sensors are notorious. You can check them and know within 99% certainty if they are toast without removing them. Pull the connector (which is readily reachable because its a foot or so from the sensor itself on the wire) and simpy check the DC resistance with a multi-tester. Each one should be in the neighborhood of 600 ohms. (anywhere from 400 to 1,000 ohm is close enough). When they die, typically they go open circuit (or close), so you would get a resistance reading between 10,000 ohms and infinity."
     
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  13. srephwed

    srephwed F1 Rookie
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    I just assumed that when the engine quit and the tachometer went to zero the two were connected. Sometimes I wish I could speak Italian.
     
  14. afterburner

    afterburner Formula 3
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    On the QV, a single rpm sensor feeds both ECUs with the same rpm information.
    The rev counter is then driven by a separate signal off the front bank (cylinders 5-8) ECU via pin #10 of the multiplug (brown-black wire). The other ECU plug doesn't have that wire.
    Therefore rev counter issue COULD also indicate a front bank ECU problem.
     
  15. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    There are only two flywheel sensors on a 3.2 (which has only one MicroPlex ignition ECU). That (the unplugged resistance test) is the easy first diagnostic test. The next level of functional testing is measuring the AC voltage of each sensor (while still plugged in) during starter motor cranking -- the TDC sensor should be something like 0.2 VAC and the Tachometric sensor something like 2.0 VAC.
     
  16. Rifledriver

    Rifledriver Two Time F1 World Champ

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    #13 Rifledriver, Oct 24, 2014
    Last edited: Oct 24, 2014
    Steve, my thought was if it is intermittent an in car test will probably show the correct resistance. In cases of suspected intermittent opening of the winding we have usually taken them out and read resistance while tapping the sensor on a hard surface. It's a pretty foolproof test provided the hard surface is not steel.
     
  17. Rifledriver

    Rifledriver Two Time F1 World Champ

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    Well they are but I was just pointing out the sensors purpose is not just to drive the tach. It feeds the entire system that info.
     
  18. dfranzen

    dfranzen Formula 3
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    Steve/ Brian,

    Thanks !
    Thats my Saturday project is to remove and tap while watching the ohmmeter

    I read read greg328 post about hardstart and it sounds similar to mine.

    On the mondial is there better access to the front bank position sensor through the access panel inside the car?

    Is there a particular sensor reccomended ?
     
  19. Rifledriver

    Rifledriver Two Time F1 World Champ

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    The tachometric sensor is the only one on a QV that will kill the whole motor. A bad position sensor will only turn off one bank.
     
  20. dfranzen

    dfranzen Formula 3
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    #17 dfranzen, Oct 24, 2014
    Last edited by a moderator: Sep 7, 2017
    I think this is the tachometric sensor that could be the culprit

    doesnt seem to be enough space to pull it out with the braided oil line in the way

    does the oil line have to be removed?
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  21. dfranzen

    dfranzen Formula 3
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    #18 dfranzen, Oct 29, 2014
    Last edited by a moderator: Sep 7, 2017
  22. dfranzen

    dfranzen Formula 3
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    IT WAS THE REAR BANK FLYWHEEL SENSOR!!!

    Put another one in and cranks first turn!

    lessons learned:
    go at it from the wheel well
    loosen (take off)the stainless oil hose brackets
    DONT TRUST THE RESISTANCE READING!

    I bought another sensor before I had even checked the resistance based on comments above in this thread. Basically I just started removing the old sensor without ever taking measurements.... I became frustrated in removing the sensor from the plastic bracket on top and decided to just take a measure and tap it while it was hanging in place ..resistance seemed normal and did not change with tapping...I measure the one I just bought (it was used but told it worked) and it measured the same...now I started BUMMING thinking that I just spent money for nothing or worse bought one with the same problem

    So I went ahead and installed the purchased one without dressing it through the engine and plastic holder turned the key over and BAM started on first turn!!! did this several times start and stop with instant first start!!
     
  23. dfranzen

    dfranzen Formula 3
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    #20 dfranzen, Oct 30, 2014
    Last edited by a moderator: Sep 7, 2017
    First pic is the view from the side notice the oil bracket nut 17 mm that had to be taken off also there is a 14mm nut to take off for better accessibility to rear sensor and the connectors

    the second picture shows how my oil hose is tilted across the sensor..I tried to loosen and straighten but the oil hose nut wouldnt budge and taking off the brackets gave me enough wiggle room
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  24. dfranzen

    dfranzen Formula 3
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    #21 dfranzen, Oct 30, 2014
    Last edited by a moderator: Sep 7, 2017
  25. dfranzen

    dfranzen Formula 3
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    figured out the wire holder had to really push at the base and flip it up at same time

    rerouted new sensor harness

    installed new red connector housing

    EVERYTHING BACK TO NORMAL!


    few things I learned about the flywheel sensor - the true characteristic is how strong the magnetic field (gauss level)
    it can still read the correct resistance around 750 ohms but over time the gauss level of the magnetic material drops and this is what causes the eddy current not to be read correctly, a square wave will still be produced but not at a high enough level that the ignition circuit reads correctly hopes this helps
     
  26. dfranzen

    dfranzen Formula 3
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    so after replacing the rear sensor unit car ran ok for couple days then the hard to start came back

    So checked fuel pump connections,
    seemed ok although I tighten it a little more

    Then I changed the relays labeled Fuel Pump relay and the Fuel Pump Starter relay

    with NAPA PN AR272 $10 each

    gotta say after 2 weeks of test driving on a daily basis my starting issues have gone away

    starts after a few seconds of turning key both cold and hot (no holding down the gas pedal)
     
  27. F-car

    F-car Karting

    Feb 25, 2009
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    Hi. I'm having hard start issue with my '87 3.2. Both cold or hot start needs to crank for a few seconds with gas pedal at halfway position. But if I restart the engine within a few seconds after turning off the engine, it fires up immediately. Battery & accumulator are new. CSV was disconnected. Any idea what's the problem? Thanks.
     
  28. dfranzen

    dfranzen Formula 3
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    have you replaced the relays that I mentioned?

    fyi I was having to hold pedal down to get started but after replacing these relays all I do is turn the key
     

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