GT4 + Pertronix= acceleration stops at 3500 -- issue | FerrariChat

GT4 + Pertronix= acceleration stops at 3500 -- issue

Discussion in '308/328' started by sammyb, Mar 11, 2018.

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  1. sammyb

    sammyb Formula 3

    Jun 23, 2006
    1,857
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    Sam
    Almost two years ago I put a Pertronix Ignitor II on the 308 GT4, and I've driven it about two miles total since. I've yet to solve an issue: the car starts and idles and will rev in neutral just fine. Once under load in any gear, when it hits about 3500 rpms, the engine totally breaks apart (rapid stumble) like a machine gun and won't accelerate further. It's fine under 3500 rpms. Choke doesn't affect it. Seems ignition not fuel related. Always the same RPMS.

    - I have checked timing.
    - The coils are new (Pertronix coils)
    - The module with the two triggers is on the rear bank and wired for the front bank.

    I'd love to finally get back to driving this at some point. I've been so busy with importing JDM cars and buying/selling collector cars with the business I started last year, that I haven't even touched the GT4 in so long. (Did drive the 328 GTS last week though!)

    Anyone have this issue in the past with the Pertronix?

    Any ideas?

    Thanks,
    Sam
     
  2. absostone

    absostone F1 Veteran
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    Jul 28, 2008
    9,182
    Hi Sammy. Sorry I cant offer advice on this and I remember from a while back you have been dealing with this. But just wanted to say hi to a fellow Avorio fellow. mike 09966
     
  3. kiwiokie

    kiwiokie Formula 3

    Aug 19, 2013
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    John McDermott
    Have you checked the mechanical advance in the distributors? Have you put the distributor with the Pertronix on a distributor machine to check its output? Might also check your 12v supply to the coils. Previous mechanic ran new 12v supply to coils because the factory wiring was only delivering 8v which was insufficient for the Pertronix to function.
     
  4. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    Sam
    The advance seems to be working. Unfortunately, it is REALLY HARD to find someone with a dizzy machine these days, especially one that actually works! That's a good idea to recheck the power supply with a meter. While I'm pretty sure I did check it for 12V, I can't honestly remember well enough to be sure.
     
  5. kiwiokie

    kiwiokie Formula 3

    Aug 19, 2013
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    John McDermott
    Not sure where you are located but if you Google “distributor recurve service” you should find a list of businesses that should have a distributor machine.
     
  6. scowman

    scowman Formula 3

    Mar 25, 2014
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    Stu Boogie
    I ran into a similar issue. Move the pertronix to the other dizzy. It will have different advance curve. If same problem then it's not mechanical advance. It's not that hard the second time

    I would suspect bad electronics. Did you replace the coils? Marellis are not in spec for pertronix. Get their flame thrower epoxy units made for lying down.

    Pertronix itself could be bad. Replace that with a spare if you can.

    It could also be fuel starvation.
     
  7. derekw

    derekw Formula 3
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    Sep 7, 2010
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    Hi Sam, Are you sure the rotor is pointing at the plug wire metal lug in the distributor cap when advance has kicked in? It might be that once advance kicks in fully the rotor is too far from the metal lug. You may need to move the pertronix sensor so that the rotor is a little before the lug at low rpms so that it is still close enough to the lug once advanced.
     
  8. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    Sam
    The rotor phasing idea is a good thought, Derek, but why the difference under load vs. revving in neutral?
     
  9. GavC

    GavC Formula Junior

    May 9, 2004
    492
    Lincolnshire, Englan
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    Gavin Culshaw
    I had a similar issue that it would rev ok when static but under load would miss. I traced it to my voltage regulator. Which was kicking out 18+v under load and finally blew the Pertronix unit. Worth putting a meter on the coil feed to see if you are getting 12v and rev engine and note any difference or check to see if your lights are glowing v bright or pulsing.
    Though as the other posts have mentioned check mech advance in dizzy.
     
  10. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    Sam
    Thanks GavC. Will do!
     
  11. scowman

    scowman Formula 3

    Mar 25, 2014
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    Again I emphasize the stock coil setup is OUTSIDE the specs for the pertronix units. Just sayin....
     
  12. scowman

    scowman Formula 3

    Mar 25, 2014
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    #12 scowman, Mar 15, 2018
    Last edited: Mar 15, 2018
    +1. You may have replaced the dizzy unit one tooth off. Could that cause the rotor to move past the cap pole during mechanical advance? Then the static one tooth advance/retard would be partially compensated by rotating the dizzy back to max adjustment when timed after assembly? Would the timing still line up at lower rpm? Maybe. Then at higher rpm it moves past the cap pole and cuts out. Maybe.
     
  13. GavC

    GavC Formula Junior

    May 9, 2004
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    Gavin Culshaw
    Agree. I have flamethrower coils also!
     
  14. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    This was the first thing we checked. The way my car is, if I'm one tooth off, the correct timing can't be hit, as it is right towards the edge of the adjustment.
     
  15. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    What's killing me is that as soon as I started thinking about getting on this again this week, I had to pick up two more cars at the Port of Tacoma for my collector vehicle dealership that I started last year. (Class Winners Collector Vehicles / classwinners.com and on Facebook. Y'all will love the banner on the company web site.) Now I'm on prepping these vehicles --a 1991 Nissan Figaro and 1992 Mitsubishi Delica Star Wagon Chamonix Edition. I keep looking over at the GT4 and saying "I promise I'll get back to you!"
     
  16. scowman

    scowman Formula 3

    Mar 25, 2014
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    Unless it's the other way?
     
  17. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    Going by the marks and trying to hit it towards the center of the sweep, the tooth it naturally falls into puts it too far advanced...and going full retard on the adjustment puts it right near the correct timing, but is still too far advanced of spec. Dropping to the next tooth and going far to the rotation adjustment for advance puts it spot on.
     
  18. derekw

    derekw Formula 3
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    The sensor should be moved on the distributor base plate so that it initiates a spark when the rotor is pointing directly at the pole on the cap. Engine load affects the ignition circuit so it could be that at higher loads the spark is finding an easier path than jumping the gap from the rotor to the pole, through the leads, across the plug etc.
     
  19. derekw

    derekw Formula 3
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    ...easy way to check is mark on the distributor where the poles are and then, with the cap off, connect the coil lead to a plug lead, put a timing light on that lead and turn over the engine while pointing the timing light at the distributor.
     
  20. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    Yup -- we did that, but it was about 16 months ago. We were spot on at the time.
     
  21. scowman

    scowman Formula 3

    Mar 25, 2014
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    Did this ever get sorted?
     
  22. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    Once again, my other obligations have gotten in the way. A little over a year ago I started a collector vehicle dealership (boutique) focusing on rare and foreign market cars. Let's just say that I'm looking at first-year 928 5-speed wiring diagram on another screen and spent today a) restoring seats on a Nissan Figaro b) cleaning the headliner on a Mitsubishi Delica Star Wagon 4X4 and c) tweaking the carb on a Suzuki Mighty Boy while the GT4 sat there with a '65 Mustang hood resting on its top.

    So I'll try to get at it next week!
     
  23. scowman

    scowman Formula 3

    Mar 25, 2014
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    Living the dream. I always wanted a Nissan patrol.
     
  24. sammyb

    sammyb Formula 3

    Jun 23, 2006
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    I finally got a 15 minute stretch in my shop where I had nothing to do, so I decided to check the GT4 for voltage at the coils. 12V key on and 13.1 with the car at fast idle (choke on.) Yes, I actually started the car up for the first time in months and it fired pretty quickly.

    I decided to advance the timing a little to see what would happen. Smoothed out the idle. There's always the possibility my old borrowed Craftsman timing light was a little off. I am at the very end of the dizzy adjustment right now, so I might take the car out and see if that moved the stumble up the rev range the next time I have a break in the weather (and have no car blocking it preventing it from getting out...it is between garage doors right now.) If it did, I can move a tooth and see if I can still start it.

    A little adjustment here, a check there. All I need is enough time to dedicate to tinkering on this specific car.
     

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