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Hot (No Start) Issue - Need A New Direction

Discussion in '308/328' started by BrockBenson, Jun 29, 2019.

  1. BrockBenson

    BrockBenson Karting

    Oct 18, 2018
    72
    Australia
    #76 BrockBenson, Aug 8, 2019
    Last edited: Aug 8, 2019
    Hi Ferrari Chatters,

    Finally made some progress today. I think we now know the “what” and all that remains is the “why”?

    Based on all your latest feedback I did the following. Started the car cold this morning (started instantly like usual). Let it get to operating temperature. Switched it off and let it sit for 5-10 minutes. Tried starting it three times, no good!

    I removed the cold start valve to use the port in the manifold for some testing. Put my thumb over the open port and had a friend try start the car three times – no good! I took my finger off the port and my friend tried starting the car and it fired to life (whoo-hoo!). We tried this three more times during the following hour, just to make sure it wasn’t a freak occurrence. It started every time with the extra air coming in through the cold start valve port. If I kept my finger off the port after starting the car would idle pretty high, if I blocked it after starting it would drop and stabilise around 950 rpm.

    So I believe we now know what the problem is: too much fuel when warm (but maybe too much fuel when cold though doesn’t have as much effect?)

    So this got me thinking about why this is happening. I hooked up my old Edelbrock air/fuel meter (used to be fitted to my drag car) using the Ferrari oxygen sensor that’s part of the lambda system. See first screen shot below, it was running so rich it’s off the scale (meter reads right to left – leaner to richer) with the car idling, cold start valve re-installed it was <12:1 ratio (or .94v using the multi meter)

    So as a test I unplugged the frequency valve with the engine running, the engine changed note a little and smoothed out. The air/fuel meter then stabilised at 14.5:1 – pretty much perfect stoichiometric mixture at idle. See second screen shot below.

    So all that remains is “why”. Why am I running rich? Could it be just an adjustment? Maybe the mixture adjuster (in the fuel distribution unit) has been messed with by the previous owner? I was going to adjust it leaner enough to allow the frequency valve to be plugged in and get a reading around 14:1 on the air/fuel meter? Or is something just faulty that is causing this? The frequency valve? The thermo-time switch? Something else?

    Happy to take some advise on this.

    Cheers, BB
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  2. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Morning,
    I use an Innovate air/fuel gauge (I'll post pictures). Very easy to use and very accurate, gauge comes with a wide band oxygen sensor.
    Procedure: remove your sensor, power the gauge( comes with many wires, but all you use are the red and black ones, red to positive and black to negative...This is you're choice, alligator clips to battery, plug to cigarette lighter...etc. Calibrate the wide band sensor as recommended by manufacturer (Instructions come in the kit). Install the sensor in the bung as the original, start the car and let it get to operating temperature( you can use the throttle to hurry this up, it wont bother the sensor). let it idle and look at the gauge. If it's not between 14.5 and 14.7 it's off. When adjusting don't go lean in between 14,5 and 14,7 is perfect.

    Hope this helps,

    John.
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  3. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    By the way, forgot to mention, between adjustments you need to remove the hex wrench and plug the adjustment hole( I plug it with my finger), blimp the throttle a couple of times and let it settle back to idle. If you don't plug the hole, you create an air leak( false reading and engine runs bad or stalls).
    Once achieved, stop engine, remove sensor and reinstall original sensor, plug the adjustment hole and reconnect the black wire.
    Also to mention, when you remove the original sensor at the beginning of the process, disconnect the black wire that comes from the sensor.
    Sorry I skipped all this before.
    All this can be done in about an hour.

    John.
     
  4. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Wow! that's very old, although looks like new.
     
  5. BrockBenson

    BrockBenson Karting

    Oct 18, 2018
    72
    Australia
    Hi John, thanks very much for your help and information. As you can see by my last post, we are both on the same track. The Edelbrock unit I have would be from the early 90's. It used to be installed in my drag car for a bit of last minute track tuning. I think it is narrow band though. The oxygen sensor died years ago, and I had forgotten I had it until this problem came up. From memory it was pretty accurate as I used to do major tuning on my friends dyno, and his dyno oxygen sensor pretty much matched my little Edelbrock unit. So I just used the signal wire from the Ferrari OEM oxygen sensor. I also measured the signal from the oxygen sensor using my multi meter, which gave me a .94V reading. Which as Steve mentioned about, means it rich. A couple of questions:
    • I'm curious, do you have lambda system of your Ferrari? If yes, do you unplug the frequency valve before adjusting the mixture?
    • Also, how coarse is the adjustment? Do you give it full turns, half turns or less between checking mixture?
    Thanks, BB
     
  6. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    18,330
    Texas
    Full Name:
    Steve Magnusson
    No (although unplugging the frequency valve will lean things out a bunch as this drops the duty cycle to 0%). You unplug the O2 sensor during warm idle which causes the injection ECU to set the frequency valve duty to 50% and run open loop when you make the mixture adjustment.

    It's a very sensitive adjustment. 1/8~1/4 turn is a huge adjustment. The usual challenge when making a final fine adjustment is to move it so little but still actually move it.
     
  7. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Morning guys,
    If the air fuel mixture is adjusted correctly, when you unplug the oxygen sensor while the engine is idling and fully worm you will notice no change on rpm or engine sound. If there is a change, it's out of adjustment. Adjustment is slightly above 14.7 to 1... the narrow band sensor cannot read if adjustment is "way out" of that range.
    Ferrari recommends adjusting the mixture to 0.7 +/- 0.2...14.7 to 1 would be 0 (perfect combustion), so adjustment using the Innovate gauge would be slightly richer than 14.7...SLIGHTLY"

    Hope this helps.

    John.
     
  8. BrockBenson

    BrockBenson Karting

    Oct 18, 2018
    72
    Australia
    Well, after much frustration it appears the issue is now solved. Thanks for all your input and in particular steve magnusson, hinecker, yelcab, kiwiokie and kcabpilot. It’s a bit embarrassing after all that work to find out that the primary cause for the no hot start was fuel mixture. After hooking up the AFR meter and seeing it pegged at 12:1 (could have been even richer as the meter doesn’t show lower) I decided to make the adjustment. With the oxygen sensor unplugged and therefore in open loop, I ended up needing to give the mixture screw ¾ turn out (in steps) to get the AFR to the 14:1 – 14.7:1 range. Also adjusted the idle down from the 1300 rpm to 1000 rpm. Did several hours of driving over the weekend, lots of hot starts….. and it started every time :):):)

    Lessons learnt. Don’t be intimated by the make of car. Its still a combustion engine that needs fuel and spark. Before replacing any parts check to see if it’s getting fuel, and if it is, is it getting the right amount. The suggestion of pulling an air hose off the manifold was brilliant. It allowed the engine to start while hot and pointed me directly to the issue. Too rich! I was surprised the Ferrari engine is so sensitive to rich mixtures (but I've come from American and Australia V8 engines which I think are much more forgiving) Silver lining, at least I won’t need to replace the injectors, accumulator and check valve for a few years. And I learnt a lot more about my car and the KJet system.

    Cheers all, BB
     
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  9. kiwiokie

    kiwiokie Formula Junior

    Aug 19, 2013
    667
    Tulsa, OK
    Woohoo! Enjoy!
     
  10. BillyD

    BillyD Formula 3
    Silver Subscribed

    Feb 28, 2004
    1,333
    Pacific Northwest
    Full Name:
    Bill
    How did you set the AFR at idle? under load?
     
  11. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Morning Bill,
    I'll answer this, the manual says that it has to be at idle with engine fully worm, if the fans kick on, you have to wait until they stop in order to get a proper reading.
    So no, the adjustment is done with no load.

    Sorry I jumped in!

    John.
     
  12. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Cheers!!! great news

    John.
     
  13. BillyD

    BillyD Formula 3
    Silver Subscribed

    Feb 28, 2004
    1,333
    Pacific Northwest
    Full Name:
    Bill
    Thanks for the info, I guess I need to read that manual more. I don't know if its me or the way the manual is written but I don't enjoy reading it. I'm use to GM manuals that are written for idiots. ;-)
    My hot start problem is not as severe BBs and I set my fuel mixture under load as I recall so now I'm going to do it again but correctly.
     
  14. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Morning Bill,
    I don't like the manual either, it's contradictive and you have to read the whole manual to find what you're looking for.

    Well... it is what it is, at least we have a manual.

    John
     
  15. Bobbytinvab

    Bobbytinvab Karting
    Silver Subscribed

    Jan 22, 2010
    236
    Virginia Beach, VA
    Full Name:
    Bob T
    Wow ... I've been away from the forum for a while and really was happy to see this thread. I've been experiencing a hot start problem for sometime, and my 85 US QV smells rich as well. I'm convinced that a previous owner has "tweaked" something incorrectly. Lots of things were not not properly connected and or bypassed ... Sigh!!

    Thx to everyone who contributed here and especially BB for telling us what fixed his problem. So many times the threads just stop without resolution, and you don't know what it took to fix it. I'm re-engergized to play with my car again to see if I can fix it.
     
  16. Hinecker

    Hinecker Formula Junior

    Mar 14, 2011
    290
    Morning Bob,
    Happy this helps, Good luck!

    John.
     

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