69 Riviera cuts out unexpectedly

Discussion in 'Wet behind the ears??' started by Woodsy, Sep 13, 2020.

  1. Woodsy

    Woodsy Member

    Hi all, this is my 1st post so hopefully there will be an answer out there. My 69 Riviera runs lovely but in recent weeks the engine cuts out and I’ve been finding out how hard these things are to stop and steer when you have no power.

    It starts perfectly well, drives superb then nothing. There is quite a strong smell of fuel but no fuel leaks. I changed the filter last week which made a difference (or so I thought) until today when I drove it and then - nothing, the engine died again. Left it sitting for a few minutes, turned it over, nothing. Left it a few minutes more and it sparked back into life. Definitely sounds like a fuel problem but that’s where my knowledge ends. Any help/suggestions will be greatly received.

  2. Michael_G

    Michael_G Living the Dream... Fast with Class...

    WELCOME! ...and someone much smarter than I will be along. That said, it could be a number of things. Does the car backfire when she tries to start? When she does run, does she idle? How long does she run before she cuts out? Have you looked at the plugs? When she won't start, will she try and start with starter fluid? I'll assume she's still using points? An intermittent spark would give a strong smell of fuel; but if she starts back up after sitting it does sound like a fuel flow issue from either an internal carb problem; partially clogged fuel line from the tank or a failing fuel pump.
    Woodsy likes this.
  3. Woodsy

    Woodsy Member

    Hi, thanks for the reply. No backfire on start up or when running. The car idles beautifully, no misfire. The car has run perfectly the last few weeks but cuts out at anytime. I haven’t tried starter fluid as it starts again quite soon after cutting out. I will check the plugs but haven’t done so yet and yes, still uses points. Now, a few weeks back I used carb cleaner and loads of black smoke/stuff came out the exhaust but when running normally, there is no smoke at all. The car has never cut out before I used carb cleaner and was wondering if it was linked to that. When it stopped today and restarted, there was loads of black smoke coming out the exhaust on Initial restart then no exhaust smoke at all after that, just back to normal running. Hope this is clear :)
  4. Briz

    Briz Platinum Level Contributor

    Black smoke is a sign of running rich. probably loaded up from trying to restart Check all connections to the dist and coil. Replace points and condenser if its not been done in recent memory. Pull the plugs and clean / replace if really fouled. Next time it quits check for spark at the coil wire asap. That will narrow it down.
    Woodsy likes this.
  5. Woodsy

    Woodsy Member

    Thanks for the advice, I’ll give it a go and report back.
  6. Michael_G

    Michael_G Living the Dream... Fast with Class...

    I had a 77 Pontiac Bonneville that ran great until the plugs started foul. Then I had issues similar to yours until I replaced the plugs. One easy to way to ensure your getting correct spark is to attach a timing light to each wire while cranking. As @Woodsy stated, I'd initially focus on the distributor components. Something may be failing once hot.
    Woodsy likes this.
  7. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Check the power supply (12 v) to the coil. Make sure it's not loose.
    Last edited: Sep 13, 2020
    Woodsy likes this.
  8. Woodsy

    Woodsy Member

    Thanks a lot of comments are pointing towards electrical components. Might be a good place to start.
  9. Woodsy

    Woodsy Member

    Thanks I’ll give it a try
  10. Nailhead in a 1967

    Nailhead in a 1967 Well-Known Member


    you know that the 1969/1970 rivieras have an electric fuel pump in the tank?
    there is an access hatch in the trunk floor

    if i remember well, the fuel pump stops working when the oil pressure is too low
  11. Woodsy

    Woodsy Member

    Thanks for the reply and you do remember well. I imported the car 2 years ago into the uk and had a new tank/pump etc then. I also had a oil pressure gauge fitted and pressure is good at speed and quite low at idle. It only cuts out at speed, well, over 20mph really.
  12. Nailhead in a 1967

    Nailhead in a 1967 Well-Known Member

    now i remember: you were introduced by adam, showing a video of your car and that knocking noise.
  13. FLGS400

    FLGS400 Well-Known Member

    If it's not the low oil pressure/fuel pump thing or condenser, see if you can borrow a known good coil from someone, and try swapping it for yours the next time it cuts out. I had a similar problem with a Nova and a Camaro, back in the day. As soon as the coil got hot enough, it would fail. Once it cooled down the cars would start right up. Replaced them with a quality new one and the problem went away.

    Welcome, by the way!
    Woodsy likes this.
  14. Woodsy

    Woodsy Member

    I was and I’m still waiting for the centre bearing to be repaired/replaced
  15. Woodsy

    Woodsy Member

    Thanks for the advice and welcome. Most comments are pointing towards electrics so I’m ordering a new coil and associated parts from Rock this weekend to see how that goes. Thanks
  16. riv2x4

    riv2x4 Well-Known Member

    Had similar situation on my 64, turned out to be a broken wire on my condenser. Replaced and no issues since.
    Woodsy likes this.
  17. black70buick

    black70buick Well-Known Member

    Do not trust the oil pressure switch to make good contact allowing the fuel pump to run reliably. I've shared this before, even a new old stock oil pressure switch will not provide sufficient current through the contacts to allow the electric fuel pump to run well. I've had no luck with the original setup and chased fueling issue for years until I discovered this, I had even run a mechanical fuel pump and simply faced severe vapor lock issues. My electric fuel pump is now connected through an ignition controlled relay - all problems solved and car runs great. Create a direct power connection to the fuel pump and test. This may not completely solve your issue but it is something I recommend. Next I would simply dis-assemble and clean the carb.
  18. black70buick

    black70buick Well-Known Member

    I guess I should explain the "why." After running an external electric fuel pump and mechanical fuel pump I finally returned to the in-tank set-up with original wiring because I felt I had tried everything else. Finally, I had a new in-tank electric pump and everything was fine for a while until the car started running hot (lean) and then I finally had a symptom similar to yours. I could drive the car at low speeds because the pump could sufficiently supply fuel under idle and light load. At high speeds the car would stall. The solution was a described in my prior post. A new oil pressure switch wasn't the solution - it is a practical safe design but unreliable. If you insist on using the oil switch allow it to trigger the relay instead of directly powering the fuel pump.
    Last edited: Sep 19, 2020
    Woodsy likes this.
  19. Woodsy

    Woodsy Member

    So it turns out my 69 had a 455 instead of the 430. Fuel pump on the side of the block which I haven’t taken off yet but repaired the fuel delivery pipe as it was split. Going with the electrics comments this car has a different distributor set-up which I’ve not come across before and seem to be struggling to find parts for. The internal coil has a stamp on it which I assume is the date (85). Has anyone come across this type of distributor before and know of any issues with them. I cleaned up the contacts and associated wiring and the car started on the button and ticked over beautifully. Took it for a drive at low speed and was perfect, clean exhaust gasses. Don’t think the problem is solved and will have to take it on a long drive but discovering new things all the time.

    Attached Files:

  20. Nailhead in a 1967

    Nailhead in a 1967 Well-Known Member

    that's a HEI distributor, did the previous owner replace the resistor wire?
    HEI needs the full volts

    the wire runs from the fire wall to the BAT terminal on the HEI distributor

    i had a '68 riviera with HEI conversion and the same problem, turned out to be the resistor wire that was still in place

    first time for the HEI in a riviera was 1974, other buicks switched one year later from points to HEI
    Last edited: Sep 20, 2020
    FLGS400, Woodsy and docgsx like this.

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