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  1. #1
    Join Date
    Apr 2021
    Posts
    13

    Default Timing or Carb Issue

    1989 Supra Mariah with the Ford pcm 351. Electronic ignition (installed by others). Rebuilt motor with about 360 hours on it.

    I've figured out my no spark issue during ignition. However, I still have somewhat of a problem. The motor is very hard to start from cold. Itll fire the first time after pumping the throttle twice, but it runs really rough and sputters. Once the motor is warm though, it'll purr like a kitten and have no problems starting.

    My question is, where should I start on getting this "last" issue figured out? I know the previous owner messed with the timing, but that is about it. I should note that it will idle around 1200 rpm while in neutral, and around 600 rpm while in gear. I have yet to diagnose any choke related issues, but I know the plate is open more than the "just a hair" that is usually recommended when cold.

  2. #2

    Default

    Did they upgrade the coil to go with the electronic ignition. I did the same thing in mine and from what I understand the stock coil can not handle the hotter spark from the electronic ignition. Also the spark plug gap will change with the new ignition.

    Not sure if either of these things will fix the issue but I know when I did my new ignition these factors came into play and resulted in a much better running boat. Timing was all a huge factor to get dialed in if they where not careful installing the ignition and getting it dialed in it could be off.

  3. #3
    Join Date
    Apr 2021
    Posts
    13

    Default

    I actually just replaced the coil, but it was more or less a stock replacement coil for the 351 Ford. What gap did you set the plugs to? I set all of them to 0.035" I believe. Most of the gaps were a lot smaller.

  4. #4

    Default

    I don't recall what the gap was...I think it was like .4 it was listed in the distributor install directions. I used a pertronix flame thrower coil, the reason I have found for an upgraded coil was because the liquid in the stock coil can not handle the heat and will get to hot and potentially fail. So the more performance coils are able to withstand that.

  5. #5
    Join Date
    Apr 2021
    Posts
    13

    Default

    Yea I just found the gap spec. Mine is close enough that I doubt it is really the issue - especially with a brand new coil installed.

    I'm wondering if I am simply not starting the engine correctly. I pump the throttle twice and leave it in neutral / closed when starting the motor. Engine will fire the first try, but will sputter and eventually die.

  6. #6
    Join Date
    Aug 2019
    Location
    St. Louis , MO
    Posts
    100

    Default Carb issue

    Quote Originally Posted by asmithcveg View Post
    Yea I just found the gap spec. Mine is close enough that I doubt it is really the issue - especially with a brand new coil installed.

    I'm wondering if I am simply not starting the engine correctly. I pump the throttle twice and leave it in neutral / closed when starting the motor. Engine will fire the first try, but will sputter and eventually die.
    In my opinion, it something with the choke settings. If it runs smooth once its warmed up, I wouldn't be looking at timing or ignition. With the engine cold, start it and observe the position of the choke plate and see if its closing or slowly opening like it should. My 89' had a decent amount of tension on the choke spring when cold, and slowly opened in about a minute I believe. Still had the original choke spring when I sold it. I rebuilt the carb twice in the 24 years I owned it. Very simple if you are mechanically inclined and take your time.

  7. #7
    Join Date
    Jul 2007
    Location
    Flowery Branch Georgia
    Posts
    2,639

    Default

    I agree it sounds like a Choke issue. Where are you located?

  8. #8
    Join Date
    Apr 2021
    Posts
    13

    Default

    I'm located in northwest arkansas. Now that I'm thinking about it, the choke plate never opens or closes - it more or less just stays in the same position. Now this is worrying me a bit because the motor runs beautifully once warm with the choke plate semi closed.

    I'm going to head out there today and see if I can confirm or deny the electric choke functions. Hopefully a local auto parts store will have a replacement in stock.

    Edit: After watching Skidim's video regarding adjusting the holley carb, there is definitely something up with my choke. I didn't realize you should be able to easily actuate that flap with light finger-applied pressure. That is definitely not the case with mine.
    Last edited by asmithcveg; 05-27-2021 at 10:42 AM.

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