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308 Carb - Hard start after several days sitting

Discussion in '308/328' started by Nuvolari, Mar 25, 2021.

  1. Nuvolari

    Nuvolari F1 Veteran
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    Sep 3, 2002
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    I've been struggling with a small problem and thought I would turn to the F-Chat brain trust for help.

    A couple of years ago I did a full engine out service on my 1977 308 GTB which included re-built heads, re-built carbs, belts, hoses, etc. It was a very comprehensive service and an opportunity to verify the health of everything. Once the car was put back together I got the carbs nicely set up and used O2 sensors in the exhaust to get the carburetion perfect.

    Once started the car runs flawlessly. It idles perfect and has zero flat spots during acceleration right to redline. Temperatures and pressures are all good and the compression and leak down numbers are super strong. Ignition cap and rotor (single distributor) are in excellent shape and the spark plugs (NGK BPR7EIX) are new and have been again recently replaced. From a mechanical perspective I can't point to any system that is not operating correctly.

    Now for my problem, if the car sits for any more than a couple of days, it is difficult to start and floods easily. My starting procedure is as follows:

    1. Choke is never used and never has been
    2. Turn the key until the fuel pump runs
    3. Wait at least 10 seconds for the floats to fill and for the fuel pump sound to change (historically a sign the floats are full)
    4. Press the accelerator once to prime the engine via the accelerator pumps (I also tried no presses and 2 presses with no difference)
    5. Crank the engine until it catches (often requiring multiple long cranks)
    6. When it catches carefully feather the throttle for the initial ignition to take hold. This is a delicate balancing act but once the engine starts and is given a rev or two to 'clear its throat' then everything is fine. Often times the engine will die while trying to get it to stabilize so another crank of the starter is needed.

    The problem is that if you don't get this just right it goes down a path of the engine flooding which requires time to sort out. Engine temperature does not matter as the car will start perfectly after 1 day but not after 2 or more.

    The question is what is it about the car sitting for several days compared to 24 hours that would cause a major difference in how easily it starts? Any help or ideas would be appreciated.
     
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  3. pshoejberg

    pshoejberg Formula 3
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    Drive the car every day and the issue is solved:). Joke aside, Weak ignition could maybe be the culprit?

    best Peter
     
  4. Nuvolari

    Nuvolari F1 Veteran
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    I thought that weak ignition could be it because of course the car needs the strongest ignition the longer it sits. During the service I did clean the cap and rotor (nothing untoward found) and did replace the spark plug leads. The ignition coils are the same ones from when I got the car (almost 20 years ago so they are older than that) so I am not sure if they have weakened over time nor do I know how to test them. When it comes to electrics it is where my greatest weakness is with machines.
     
  5. pshoejberg

    pshoejberg Formula 3
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    I would try with a fresh coil and if that doesn’t help then trial fit a new modern ignition and conclude from that if your ignition box is weak. Sometimes it’s quicker just to through parts at it than starting extensive fault finding. I fixed my bbi starting issue that way. I know it’s Easy said by a one who were brought up with electronics for breakfast.

    best, Peter
     
  6. Nuvolari

    Nuvolari F1 Veteran
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    As it happens my car only has coils and no additional ignition box. It has always been like this and the carb 308's never got something resembling a Dinoplex from factory. I have no problems buying a couple of coils and trying them out. Now to embarrass myself. I'm not sure which coils to buy. They all look the same to me. The only thing different to stock is that I'm running a Pertronix ignition rather than points. Any recommendations?
     
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  8. theunissenguido

    theunissenguido Formula 3
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    Floats stuck in carburators ?
     
  9. jimangle

    jimangle Formula 3

    Nov 5, 2003
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    You stating that the fuel pump changing sounds leads me to believe this problem is fuel related. I had something similar until finally the car just wouldn't start and the pump motor didn't have it's usual audible tone. There was no fuel coming from the pump with it running, so I dissaembled the fuel pump and found that magnet for the motor was cracked in half and stuck in a position that it would not longer rotate. I gorilla glued the 2 halves back together reassembled the pump and the car started right up.
     
  10. Nuvolari

    Nuvolari F1 Veteran
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    The fuel pump was replaced about 2 years before the big rebuild and its sound has always been consistent. It works great and I have confirmed steady flow. The change of note is typical of carb cars when the system has air in it the pumps will sound different to when it is fully purged of air and ready to go. I think the pump is very unlikely the culprit especially as the car drives perfectly once started. Also the fuel filter was changed and the strainer in the tank was cleaned.
     
  11. JuLiTrO

    JuLiTrO Formula Junior

    Nov 2, 2017
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    Julio Saiz
    Hi!

    Honestly what you describe matches 100% the starting procedure of my 77 USA when seating for more than 1 week.

    I pump 3 times before each crank and I dont do long cranks, and it always start at the 3rd one.

    1st one there is no ignition and I dont push gas
    2nd one you can notice bit of start, it dies i dont insist nor push gas
    3rd one it ignites and help him this time with some gas

    One running I keep a bit of constant gas for 1 min max until he manages to keep the idle by himself

    5 minutes warm up and..... Go to go!

    So I think your 79 is perfectltly fine
     
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  13. Nuvolari

    Nuvolari F1 Veteran
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    On my Dino regardless of how long it sits, it fires on the first go almost as easily as any fuel injected Toyota. The only real difference is that the Dino has an MSD ignition so it delivers a significantly stronger spark. I just can't accept that the 308 would need some kind of special sequence to get it to start.
     
  14. JuLiTrO

    JuLiTrO Formula Junior

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    I actually love it. Gives caracter to the car

    Important is that he behaves always the same, if changes then something is wrong obviusly
     
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  15. pshoejberg

    pshoejberg Formula 3
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    I'm not really familiar with the early 308's points based ignition but I see that SF have a coil available for an acceptable price: Image Unavailable, Please Login

    Anyhow I most say the worse thing I know of is driving an attractive car that cannot start in a second....I simply hate it and feel a deep pain in my stomach if my cars doesn't start immediately when cranking with people around. Maybe you should consider converting to a more modern type high voltage / non points / Non mechanical advance application. I works miracles on our Dino's and you can hide the ignition box and make the rest look original. Most car manufactures turned towards electronic ignitions in the seventies for a reason so I'm a bit surprised that the early 308 missed out but not the very early Dino's from 1969. I have often heard the argument that a well adjusted and serviced points based traditional ignition works as good as a high voltage modern one but I'm not convinced.

    Best, Peter
     
  16. Nuvolari

    Nuvolari F1 Veteran
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    I saw that listing but was a little confused as I do not have points and the one below it lists 'for transistor ignition' and I'm not sure if with the Pertronix I qualify for that one. I'll pursue this ignition thing further and will look into an MSD option.
     
  17. smg2

    smg2 F1 World Champ
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    Honestly coils are coils, as long as it's producing the output voltage required for the system, good to go.

    I'm not sure it's coil related though. You mention once you've gotten running it starts fine the next day but after 48hrs or more... Not so. Electronics tend to not do that. Esp coils, those fail intermittently when hot, i.e. after running for a period of time. If I was looking at the electrics I'd look at the battery charge and the charging circuit, aka alternator output.
    What voltage does the battery drop to under starting? Does the problem go away if you put a charger on it to start? What's voltage when running?

    Then I'd look at the fuel. How old is the fuel? Condition of fuel filter? The time delay of ~48hrs could be due to something settling out of suspension in the fuel and causing issues, jets clean? Etc..

    Are you sure the pertronix is operating as it should? That's your new brain box for ignition timing. Is the carbon rod/button still making good contact under the cap? Rotor and cap condition? Plug wire resistance, plugs, extenders?

    Just the run down list I'd work thru.
     
  18. miked

    miked Formula Junior

    Feb 7, 2001
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    Mike Dawson
    Pertronix has been very popular for old British cars for a long time. I have a Triumph TR4a so I frequent Triumph forums, Pertronix has lost quite a bit of it's luster there with degraded performance and eventual failure. Pertronix was bought out by an after market parts conglomerate some time ago, you know what happens then. Not saying that Pertronix is the root of your problem, I have no experience with them (I have used Crane XR optical triggers on my GT4 for 20 years). I would look into how much spark your ignition is actually producing first before throwing parts at the car..
     
  19. Nuvolari

    Nuvolari F1 Veteran
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    Thank you for run down. I tend to agree that the coils are probably ok. All of the people I have spoken to told me that if the car runs well especially at high rpm then the coils are fine. Electrically the alternator was re-built and tested and the battery is new. The charging system is really strong and we tested the power to the coils when cranking and it was really strong.

    As for the fuel it has done it through many tanks of fuel. The fuel filter is new and the tank strainer is clean. All of the fuel lines are new too and the fuel pressure has been confirmed ok. Jets have been double checked and are perfectly clean.

    The question mark could be the Pertronix. The unit is over 20 years old and I do not know if it looses strength over time. Cap and rotor are in excellent condition and the plug wires and spark plugs are new.
     
  20. Nuvolari

    Nuvolari F1 Veteran
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    Unfortunately Crane has been out of business for several years now and I'm not sure if their system would even fit in a single distributor as I have. I'm going to have to do some more research and learn how to test my spark output. My gut is leaning to a weak spark.
     
  21. smg2

    smg2 F1 World Champ
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    There's a way to do that, but requires equipment most people don't have... Very large resistors, scope, spark gap, etc...
    There might be a machine that does it.
    Not sure what it would gain though, coil is probably just fine.

    Pertronix, testing... That's something else.
     
  22. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    On the ignition front -- what is the status of your fuseblocks? Do you have something, or made some modifications, that has a very good electrical connection between the top terminals of fuses #1, 2, and 3, or are you still relying on the stock riveted connections?
     
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  23. Nuvolari

    Nuvolari F1 Veteran
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    Fuse boxes are perfect. Many moons ago I invented the popular replacement fuse blocks which Birdman asked me if I minded if he made them to sell. The rest was history:)
     
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  24. mike996

    mike996 F1 Veteran

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    Have you examined the carb floats to ensure they are, indeed 'floating' and that the float level is correct/needle valves OK? It sounds to me like you are flooding the engine initially somehow. If a float is no longer sufficiently buoyant or the needle/seat is faulty, you could be pumping raw fuel directly into the manifold. Admittedly, if that was the case, I would expect very poor idle.

    You mentioned you don't use the choke. Is there any possibility that it is partially engaged even though it is "off?"

    If you haven't already tried this, next time, after it sits for a couple of days, get in and try to start it immediately, without waiting any time for the carbs to fill up. See if there is any improvement.
     
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  25. kiwiokie

    kiwiokie Formula 3

    Aug 19, 2013
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    Have you checked the voltage at the coils? Previous owner of my car had starting issues with Pertronix which turned out to be due to coils only seeing 8v. Solved with relays and a power feed direct from starter.


    Sent from my iPhone using FerrariChat
     
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  26. ProvaMo

    ProvaMo Karting
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    Consider removing the air cleaner cover before the car started and carefully look down the throat of each carburetor bore, have someone turn the ignition on to pressurize the fuel system, then watch to see if there is any rogue fuel dripping into one or more bores. Not to say somebody did a bad job previously, but many rebuilt carburetors may not have been set up properly. If a float is sticking, or if you have a bad needle/seat valve, you may see a drip or two happening in real time, but the car runs fine otherwise. For example, I recently discovered an accelerator pump nozzle crush washer was missing, because fuel was coming from the nozzle mounting base, and not the nozzle tip… but the car ran “fine.” Good luck and looking to hear resolution.
     
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  27. ProvaMo

    ProvaMo Karting
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    Of course, I should’ve indicated to do this procedure after the couple days of sitting where you anticipate having the starting issue....
     
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  28. Nuvolari

    Nuvolari F1 Veteran
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    Thank you all for the great suggestions. A few observations:

    - Power to the coils has been confirmed as ok including testing while cranking.

    - When the carbs were re-built the floats were checked to make sure that they were not leaking and new needles and seats were installed. Of course that is no guarantee of a proper seal so I will check these again.

    - I will try some different starting techniques that do not give the carbs time to potentially flood the engine and see if it helps. Great suggestion Mike.

    - The choke for sure is fully off.

    - I was the one the re-built the carbs and have done several but that is still no guarantee that I did not make a mistake this time around or got some faulty parts. I'm happy to second guess my work and do some more investigation. The idea of removing the air cleaner and looking down the bores is a simple test that I will do just as soon as I wait a few days. Thanks Paul.
     

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