85 Mondial QV appears to be running rich | Page 2 | FerrariChat
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85 Mondial QV appears to be running rich

Discussion in 'Technical Q&A' started by Threeofnine, Mar 11, 2024.

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  1. Threeofnine

    Threeofnine Formula Junior

    Dec 11, 2020
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    Jarrod Heath
    #26 Threeofnine, Mar 13, 2024
    I saw a thread regarding the crank position sensors. Are they fairly easy to get to? i’m going to pull the plugs again tomorrow when there’s better light and compare the difference between the two banks. I will also do a spark test. The darker plug is from the rear bank and the lighter plug is from the front bank. it almost looks to me like the front bank may be out. I saw in a different thread that a QV motor will not rev past 4k if a bank is out. Is that accurate? I believe my motor would likely go past 4K.


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  2. moysiuan

    moysiuan F1 Rookie
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    #27 moysiuan, Mar 13, 2024
    The car would not likely run well enough at all if the crank sensors were failing, so I suspect that's not your issue. They can demonstrate intermittent failure though, which makes definitive diagnosis tricky. I have the 3.2 not the QV, I think the senors are different (and 3 rather than 2 on the QV).

    But it does appear you may have one bank out. As I mentioned these are two 4 cylinder engines strapped together. The car can run quite well on 4, but you would feel lethargic acceleration, slower to rev, etc.

    One easy way to check the coil is to swap the coils on each bank and see if the problem switches sides. (New coils are available but not quite identical to the originals, and some replace the top portion of the coil only, essentially rebuilding the coil.)

    If the coil is ok, I would take that dist cap off and recheck the continuity of the wires from the cap to the plug end, make sure the resistance readings are in normal ranges for the length of each wire, and inspect the dist cap to make sure the centre graphite contact is not worn, and the spring underneath is not stuck. A rarer problem is the dist oil seal leaks, and you would see oil in the cap when you remove it. The oil messes up the electrical action.

    Your spark test would perhaps give further clues as to what might be happening.
     
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  3. Ferrari Tech

    Ferrari Tech Formula 3

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    #28 Ferrari Tech, Mar 14, 2024
    The spark plugs don't look too bad. With a lot of idling, all spark plugs are black. You don't want them to be wet and your plugs are not wet. You can pull the plug wire while the car is running and it will be heard as it starts to miss fire. You will also hear the plug wire fire jumping to a nearby ground. This can tell you a lot. If you hear a drop from all 8, move on, it is not ignition.
     
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  4. theunissenguido

    theunissenguido F1 Rookie
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    #29 theunissenguido, Mar 14, 2024
    I learned something new today ! I did not know QV having crank position sensors...or maybe it has on other name. ;)
     
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  5. moysiuan

    moysiuan F1 Rookie
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    #30 moysiuan, Mar 14, 2024
    You can measure the ohms with a multimeter with the engine off, at the sensor disconnect connectors, I think the QV has three sensors. 0 or infinite ohms means they are bad. Something like 700 ohms means they might be ok (but not necessarily).
     
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  6. Threeofnine

    Threeofnine Formula Junior

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    #31 Threeofnine, Mar 14, 2024
    I ran a spark test on all cylinders and they were all firing so it appears my bank isn’t out after all. First thing this morning, after the car sat all night and was cold, I also pulled all spark plugs to compare and they all basically looked similar in the light of day. They are all coated in junk and did appear to be at least damp with fuel. Upon startup this morning it was the usual fuel smoke and rough idle for a minute or so. The idle is staying rough and choppy pretty much all the time and an unusual amount of gas pedal is required to start moving without the engine stalling. Starting on any incline is quite challenging and the car bucks until the rpm’s cross 2k, after which it runs quite well (but maybe not optimal). I made a short video of the idle, you can see how the RPMs drop down to the 500 and 600 range, to the point where the engine is on the verge of stalling. Occasionally it will stall. The part where it crosses 1k is because I pressed the accelerator pedal.

    https://youtube.com/shorts/XMsJTtABbkE?feature=shared
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  7. Threeofnine

    Threeofnine Formula Junior

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    #32 Threeofnine, Mar 14, 2024
    Thanks Wade. I will try this later today.
     
  8. moysiuan

    moysiuan F1 Rookie
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    #33 moysiuan, Mar 14, 2024
    Great to have a better sense that the ignition is ok.

    Back to fueling problem!
     
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  9. Threeofnine

    Threeofnine Formula Junior

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    #34 Threeofnine, Mar 16, 2024
    Last edited: Mar 16, 2024
    It does appear to be a fuel issue. It is also possible I missed something ignition related. The car is going to Wade on Monday. I’m confident he will get it sorted out. I just hope he doesn’t laugh too much at the cosmetic condition haha.
     
  10. moysiuan

    moysiuan F1 Rookie
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    #35 moysiuan, Mar 16, 2024
    Good luck. I will stick with my idea of the fuel distributor plunger, and am curious what the outcome is, there is always plenty to learn with these cars. I am sure your car will run beautifully once this is sorted.
     
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  11. Threeofnine

    Threeofnine Formula Junior

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    #36 Threeofnine, May 3, 2024
    Last edited: May 3, 2024
    Update. The car still is not running right. Now it’s barely running at all. The car was sent to Wade and the fuel distributor was rebuilt again, along with the warm up regulator and the front four injectors were discovered to be leaking so they were also replaced. The fuel system was reported to be functioning optimally but the car still was not running right.

    The next suggestion was to replace the plug wires. I opted to do this myself. When I received the car back it was running exactly the same as it was prior but bad plug wires made perfect sense. When I remove the distributor cap, I found the one on the front bank was cracked.

    I was sure this was likely the cause of my issue. I replaced both distributor caps, the plug wires and went ahead and installed a new set of spark plugs. Unfortunately, there is zero change. The car is flooding so bad the only way to start it is to pull the fuel pump fuse and turn it over to clear the fuel. However, even then it will not run long before stalling, will barely idle and won’t take throttle, and there is a very strong smell of raw gas from the exhaust. What could possibly be causing it to flood so badly and any suggestions on where do I go from here?


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  12. moysiuan

    moysiuan F1 Rookie
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    #37 moysiuan, May 3, 2024
    Since some injectors were leaking, I wonder if the cold start injector is leaking as well. Even if disconnected, fuel could be leaking through it.

    That was quite the cracked distributor! Did you replace the rotor as well?

    Do recall my test in this thread for whether the fuel distributor is set up correctly. If fuel is flowing through with the engine off and pump on by bypassing the fuel pump relay, you have a plunger set up problem, or if not you can rule that problem out. There are not so many ways to have too much fuel going into the engine at idle.

    I recall there can be an issue with a clogged return line from the fuel distributor to the gas tank, I can't recall the specific thread on this, I recall it was easy to check as well.
     
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  13. Threeofnine

    Threeofnine Formula Junior

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    #38 Threeofnine, May 3, 2024
    I didn’t replace the rotors because the ones I received did not fit so I reused the old ones for now. I am going to check the CS injector tomorrow and I will also check the fuel return line. I will post back tomorrow.
     
  14. Threeofnine

    Threeofnine Formula Junior

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    #39 Threeofnine, May 4, 2024
    Another update. I don’t want to say too soon but I may have found the issue and it’s because I’m stupid. I checked all the connections again in the light of day and discovered one plug wire was not actually seated to the spark plug…

    I seated the plug wire and disconnected the CS injector. The car started right up, idled and drove beautifully. No flooding issues upon restart and no strong/unusual exhaust smell.

    I’m going to order a CS injector and go ahead and replace it.
     
  15. Threeofnine

    Threeofnine Formula Junior

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    #40 Threeofnine, May 8, 2024
    Additional update. The car ran beautifully for the first two days. On the 3rd day I felt it was running slightly worse but still not bad. On the 4th day it started up just fine but started stumbling as soon as I put load on it to back it out of the garage. It required an unusual high amount of throttle not to stall out. When it did stall, it flooded again and couldn’t be immediately restarted without pulling the fuel pump fuse to clear the excess fuel. I did also notice a return of a slight gasoline smell from the exhaust, although not near as bad as previously.

    It appears the car is becoming progressively richer. Is this possible with the mechanical injection system? I did check the CS injector and confirmed it is not leaking. I do still need to check the fuel return line.

    The spark plugs were not sooty/black and appeared to show optimal coloration upon visual inspection. My guess is the car is still slightly out of tune so my plan is to send it back toward the end of the month to complete that. Before doing that, are there any other simple things I should try?
     
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