Finally got my car! Now to work...resting fuel pressure? | FerrariChat
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Finally got my car! Now to work...resting fuel pressure?

Discussion in 'Boxers/TR/M' started by mtooze, Jul 16, 2012.

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  1. mtooze

    mtooze Karting

    Jan 30, 2009
    70
    lincoln, ne
    Full Name:
    marcus tooze
    #1 mtooze, Jul 16, 2012
    Last edited by a moderator: Sep 7, 2017
    At last, retrieved my new 512TR. Made the 2500 mile trek to PA and picked it up from Jim and its major.

    Lots of fun, love the torque, mashing it in second or third up to reline is a panic.

    I already have a list of items to fix, starting with hard hot starts. Now this is a 92 512TR, not an earlier car (so no, its not the solenoid issue, starter is cranking)...also, it has sat for quite a while, with only 10k miles on it (doesnt help).

    On hot start, after the engine has had plenty of time to heat soak, it takes 2 or 3 tries to start. The starter cranks perfectly, just for a loooong time. My backyard diagnosis is that the resting fuel pressure is not being held up. Is there is a separate check valve, or are the fuel pumps meant to hold the fuel pressure up? It does start fine cold (couple of turns of the starter).

    Next bit of info that may or may not be connected. I have a slightly hunting idle, on the tach (i havent hooked my own tack up to check accuracy), its sitting at 500 rpm or so and it hunts up at least a 100 rpm quite rhythmically). Id suspect either a small vacuum leak (perished hoses) OR maybe a sticky idle air control valve? I dont know how much the idle air control valve is used in the starting procedure yet either, so either these are linked or I have a couple of different issues going on.

    Thoughts anyone? I might start with cleaning the idle air control valve, only because its easier than pulling fuel pumps!

    Marcus

    PS here she is, fresh in on the trailer
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  2. KENCO

    KENCO Formula 3

    Nov 1, 2006
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    #2 KENCO, Jul 16, 2012
    Last edited: Jul 16, 2012
    500 RPM is way to low, that's like half of what it should be.

    "removed below by me, because of mis-information"
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    #3 Steve Magnusson, Jul 16, 2012
    Agree (especially after just being serviced), but his car is a 512TR (Motronic, not Jetronic).
     
  4. mtooze

    mtooze Karting

    Jan 30, 2009
    70
    lincoln, ne
    Full Name:
    marcus tooze
    #4 mtooze, Jul 16, 2012
    Yep...its a 92 (motronic), completely different fuel system than 91 and before (CIS right?).

    Ill do some more reading, but I think I have two seperate issues...after thinking about it, the idle air valve is (I assume) wide open on start and has nothing to do with starting, but it, or a vac leak is the idle issue (especially with the hunting).

    The hot start is most likely a "holding" fuel pressure problem...as the other OP said, on cold start, the ECU/injectors are adding extra gass anyways for starting, but once its hot, it wont do that, and relies upon the fuel pressure to stay up and stop vapor lock...

    Can anyone confirm hot idle is meant to be 800 to 900 please?

    Marcus
     
  5. KENCO

    KENCO Formula 3

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    #5 KENCO, Jul 16, 2012
    Never-mind :)

    I removed above misleading info.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #6 Steve Magnusson, Jul 16, 2012
    Last edited: Jul 16, 2012
    On page C60 in the 512TR WSM, it seems to state that the (cold start) idle RPM should be 850 +/- 50 RPM when the idle speed regulators are disconnected, and, then on page C61, that idle should increase to 960 RPM when the idle speed regulators are connected. But I didn't give a through reading to this seemingly complicated and lengthy procedure that needs a specialized tester.

    On page C21, the WSM indicates you have check valves, similar to the CIS system, on the output fitting of your Motronic fuel pumps that should hold the pressure at 1.5 bar after shutoff, but, unlike the CIS systems your fuel pumps aren't so easy to reach ;)

    You can download a copy of the 512TR WSM from www.ferraridatabase.com under "Downloads" then "Workshop Manuals".
     
  7. mtooze

    mtooze Karting

    Jan 30, 2009
    70
    lincoln, ne
    Full Name:
    marcus tooze
    #7 mtooze, Jul 16, 2012
    OK, sweet. Manuals downloaded.

    I will read and see what they have to say. Im guessing my only way to test the IAVC is to replace with new and see if anything changes. Ill disconnect andf see what happens to idle.

    The 1.5bar is easy, just hook in my gauge while its hot, run, and see where the pressure goes on shut off.

    Thanks for the directions. Marcus
     
  8. Melvok

    Melvok F1 World Champ
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    #8 Melvok, Jul 16, 2012
    My 512TR starts alway in one go ... revs up to 1100 and goes back to +- 1000 revs then.
     
  9. AlexN

    AlexN Rookie

    Jan 14, 2009
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    #9 AlexN, Jul 16, 2012
    Mel,

    Mine is exactly the same.
     
  10. mtooze

    mtooze Karting

    Jan 30, 2009
    70
    lincoln, ne
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    marcus tooze
    #10 mtooze, Jul 16, 2012
    Last edited by a moderator: Sep 7, 2017
    Mmmm. OK, is this a problem?

    Reading on page C25 it states that if the battery is disconnected, the ECU must go thru a self learning prrocedure...this is right under the description of proper operation of the idle air control valve. See attached pic of text scabbed from the manual! It specifically says that the idle air will forget its stuff if the battery is disconnected!

    I wonder if this is my problem on the idle issue!! I will try the "reset" procedure and report what happens.

    Anyone else using their battery disconnect switches?

    Marcus

    PS doesnt fix my hot start problems tho :(
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  11. mtooze

    mtooze Karting

    Jan 30, 2009
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    lincoln, ne
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    marcus tooze
    #11 mtooze, Jul 16, 2012
    Oh well, the reset procedure didnt work. Back to looking for vac leaks and the maybe testing whether then IACVs are not working right...
     
  12. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #12 Steve Magnusson, Jul 16, 2012
    Need to correct myself. The 1.5 bar was/is the opening pressure of the fuel pump check valves; the fuel pressure after shutoff should be something like ~3.8 bar (and there's another check valve built into the pressure regulators).
     
  13. mtooze

    mtooze Karting

    Jan 30, 2009
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    lincoln, ne
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    #13 mtooze, Jul 16, 2012
    great, thx...thats pretty high...60psi or so. I bet thats the primary problem as it has no problem under load, the the pumps are doing the pumping, just not the checkin'.

    I see from another thread the tanks come out thru the bottom of the car...phew...i was wondering if they might come out behind the engine which would suck balls.

    Marcus
     
  14. Melvok

    Melvok F1 World Champ
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    #14 Melvok, Jul 17, 2012
    " picked it up from Jim and its major. "

    Did you phone him already ? This should not happen after a major imo.

    Believe me, this beauty should start immediately, and always ! ;)
     
  15. mtooze

    mtooze Karting

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    #15 mtooze, Jul 17, 2012
    Yes, but I don't want to be unfair to Jim, I had not seen/driven the car before (gambled on sight unseen, with Jim doing a PPI) and he had never worked on it or seen the car before. It went into him for a major, not for hot starting/idling issues. In addition the car had sat for quite a while.

    Marcus
     
  16. Melvok

    Melvok F1 World Champ
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    #16 Melvok, Jul 17, 2012
    Last edited by a moderator: Sep 7, 2017
    Did you do some checks yourself ?

    Example: there is a "warm" water/coolant in each plenium, coloured bleu (in my car) with one connector; cost $20. (in this case 2 times sensor # 26)

    In my car, one was faulty and influenced the running; changed both and engine running was better .... for just $ 40 + some work ... ;)
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  17. mtooze

    mtooze Karting

    Jan 30, 2009
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    #17 mtooze, Jul 17, 2012
    Thx Mel. Duly noted. Do you happen to have a (non ferrari) part number? I already found the IACV bosch numbers.

    For the idle issue, I will start tonight if I have time by unplugging the O2 sensors and see if that changes the idle to see if its mixture related as a rough start. Im assuming it will go into some kind of limp mode and use a basic strategy that ignore various sensors inputs (like the O2 sensors). If that changes things, I will then go to my friends shop and hook it to a scope and see if the 02 sensors are responding properly.

    I also havent tried having the OBD to tell me if it has anything stored which might provide further clues. I may try that tonight too.

    Marcus

    PS I also read your fuel pump RR write up...superb. I will be using that to fix my probably leaky check valves when I put the car up for the winter.
     
  18. Melvok

    Melvok F1 World Champ
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    #18 Melvok, Jul 17, 2012
    Last edited: Jul 17, 2012
    Hi Marcus,

    I don't think it has anything to do with OBD or O2 sensors ....; looks to me a Motronic problem.

    Dit you perform the ECU check ?

    It will give all faults by blinks in the dashboard .... just note them and look them up ... ;)

    Look and read very thoroughly here: http://www.ferrarichat.com/forum/showthread.php?t=331907
     
  19. mtooze

    mtooze Karting

    Jan 30, 2009
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    #19 mtooze, Jul 17, 2012
    Mmm, I'll disagree with you a little bit, only because I can't discount anything until I have tested...whacky idle on motronic can be a host of things...easy to do a rough test by unplugging o2 sensors, then move onto other things.

    I will run the OBD (blinky dashboard) though...I have a US car so I should be able to just press the button :)

    Marcus
     
  20. Dr_ferrari

    Dr_ferrari Formula 3
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    #20 Dr_ferrari, Jul 17, 2012
    If it was motronic system error, you would for sure have a code and the lamp would be lit.

    there are no error lights, so I would say no error.

    problem either lies with rest fuel pressure or O2 sensors. possibly both.

    could also be leaking injectors.

    Best regards, Jim
     
  21. mtooze

    mtooze Karting

    Jan 30, 2009
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    #21 mtooze, Jul 17, 2012
    Hey jim,

    I unplugged the o2 sensors, only difference was the slight rhythm disappeared...idle level still at 500 rpm and of course, i got CEL came on for left bank...i didnt bother waiting to get to full temp as it seemed to make no difference and i assume right CEL would have come on too becuase of the missing o2.

    One other thing for the list...and im home and dont have the manual in front of me, should the AC kick up the idle RPM? If any of you have working AC, let me know. I ask as i i switched on mine to see if idle rpm would change and it did not, which makes me wonder about the IACVs again...

    Marcus
     
  22. 302Tim

    302Tim Formula 3

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    #22 302Tim, Jul 17, 2012
    I think most of us have working AC, it's a pretty reliable system (aside from fan speed control). On my 88 TR no idle RPM change when running AC though I do notice a (very) minor dip in rpm then immediate return to prior RPM when it first kicks on (maybe a needle-width).
     
  23. Melvok

    Melvok F1 World Champ
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    #23 Melvok, Jul 18, 2012
    Last edited by a moderator: Sep 7, 2017
  24. Dr_ferrari

    Dr_ferrari Formula 3
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    #24 Dr_ferrari, Jul 18, 2012
    Marcus,

    you are right, the cel will come on with the o2 unplugged.

    as for the idle, it will adjust but only mildly as the engine has so much torque it will appear to stay about the same.

    The idle should be at about 950. the gauges are notoriously inacurate if you are going by the dash gauge so I would not really trust that reading. at 500 rpm, I think the car would stall.

    I am sending you a pair of o2 sensors this week. when you get them installed, shut battery off for 5 minutes, turn back on and restart and let idle for 5 minutes for the system to reset. we will see if that helps.

    Best regards, Jim
     
  25. mtooze

    mtooze Karting

    Jan 30, 2009
    70
    lincoln, ne
    Full Name:
    marcus tooze
    #25 mtooze, Jul 18, 2012
    Jim: Oh Jim, you really dont need to do that. Really unnecessary. I was going to go to my friends shop and we were going to have a poke around next week, he has a scope, etc to look at stepper motor signals etc...again I fully expect this w a 20 yr old car that has sat and its not your responsibility at all. You have already been more than helpful. Im not so convinced of it being o2 at all yet.

    Mel: No, you are confusinf the slow down lamp with the CEL lamp...the slow down lamp is simply triggered by the EGT probe, I think that sucker has to hit 850F and it will alluminate to stop people burning up their cats....and I dont have any :)

    M
     
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