78' Ranchero Dies upon Accel

Discussion in 'Ranchero Tech Help' started by smith15333, Feb 20, 2013.

  1. smith15333

    smith15333 In First Gear

    Hello all,

    My 78' 351 Windsor Ranchero, has been having problems for about 2 years now. In high school I drove it to and from school in South Texas with very few problems. However it began to have problems as most older vehicles do. It would have trouble starting, i.e. would not fire right up, I would have to crank it for 30 seconds or so will giving it the appropriate amount of gas. Then once it fired it would die as soon as I released the key from the start position to the run position unless I had the RPM up around 3-4 thousand. I changed the ignition switch and some seals on the carb that were bent over on themselves. This made a noticeable difference in the way the ran, (much smoother). The starting issues continued off and on. Upon graduating High School I joined the Air Force and didn't drive the car for about a year while in Basic Training and Tech School. Now that I have started driving it again I am having trouble when the engine is cold, more so when there is cold weather as the engine takes longer to warm up. What happens is, the car will die if I attempt to accelerate quickly, this problem doesn't occur if the car is hot. If I try to accelerate quickly from a complete stop it will just die and not move. If I am going over 20 Mph it will die if I accelerate and get the RPM up above about 2250, (the RPM goes to 0) and when I let off the gas the car fires back up by itself. As long as I don't attempt to quickly speed up there are no problems. This is problematic as I cannot quickly get out of the way of something that is going to hit me...or do any hot rodding:) Any help would be appreciated


    P.S. It has 180000 miles on it and the engine was rebuilt around 140000
  2. ribald1

    ribald1 Banned PLATINUM MEMBER

    Check the operation of your choke. Make sure it is closing when the engine is cold.
    The choke is the top plate on the carburetor.
    If it is not closing, check for any binding, then look into the bimetallic spring assembly that operates it.
  3. burninbush

    burninbush In Maximum Overdrive

    near SF
    Hi Smith ... sorry to hear about your problems.

    Taking a few guesses ... the problems are all in your carburetor, and probably also the filter [round can] that is screwed into the front of it.

    So, first move, change that filter. This is a common failure, they get plugged easily.

    The other problems with your carb can likely all be solved by putting in a carb 'kit' -- new gaskets, float needle, etc.

    Hopefully, after that your choke plate at the top of the carb will be lightly closed when the motor is cold, and fully open when it is warm. There are various adjustments to get it set right, will be detailed in the sheet that comes with the carb kit.

    While the carb is off, investigate the egr spacer that fits under it -- those sometimes get eroded so badly by exhaust gas that they seriously leak, which will prevent you from ever getting it right until fixed. A leaky EGR valve could also cause some of the problems you report.
  4. Rancherous

    Rancherous Administrator Staff Member

    Buffalo, NY
    Possibly the tank screen also
  5. Brian Loula

    Brian Loula In Fourth Gear

    Some other things come to mind, eg. vacuum leaks. Check the vac. advance diaphragm, & the advance plate inside the dist. that the diaphragm arm attaches to, for excessive slop or play. Definetly check the choke system too. The fast idle cam is plastic & breaks, I had that effect one of my Ranch's, and the choke would tend to close upon accel. causing the car to stumble, die & just run like s@#%$. Just a few other options.
  6. bscottie

    bscottie In Maximum Overdrive GOLD MEMBER

    if you didn't do any prep before it was left to sit a good carb rebuild would be a good start, I would also change the fuel pump and any filters
  7. CLessley

    CLessley In Third Gear

    Fresno, CA
  8. plumcolr

    plumcolr In Maximum Overdrive SILVER MEMBER

    Freehold NJ
    If the tach goes to 0 but engine restarts by itself when the car slows down, you are losing spark (no spark, no tach pulse). The engine is obviously still turning as it restarts by itself when you slow down.

    Now, that may not be your only problem but is definitely one of them. Check all the ignition leads and spark plug wires especially to the coil (if you can) for breaks and corrosion.
  9. Hawghead

    Hawghead In Second Gear

    I have to agree. If it just shuts down when you get above 2250 rpm it's electrical. If it was fuel it would lose power or stumble not just shut off.
    My vote is for a bad coil.

  10. smith15333

    smith15333 In First Gear

    Thanks for all the input, some updates based on the feedback. I had the choke adjusted all the way open for summertime use, as the car didn't need to warm up per se. I changed the ignition coil not too long ago. Spark plugs were the first thing I changed. In response to Hawghead, it immediately fires back up upon letting off the gas, no slowing down necessary. The choke/vacuum leak sound very suspicious, the choke was always my first thought as the dying was similar to driving an old tractor and leaving the choke out after it has warmed up...it dies. I'm really hoping its not a vacuum leak as that will be all kinds of fun to find. Rebuilding the Carb always sounds like a safe bet and wont hurt it any for sure. I will probably end up selling her, but I would be nice to get some of the power back for a few joyrides before I do that.

    Thanks for all your help/future help

  11. Union Laker

    Union Laker In Second Gear

    Detroit USA
    Get a new accelerator diaphram all you need: Easy to change out.
    Those carbs always work great. Then start replacing worn vacuum lines.

    They are a cheap fix.

  12. RICH

    RICH In First Gear

    Warm/up Stall problem

    I have a 78 with the same problems, My friend has been working on it and improving the problem, choke adjustment was re-worked slight improvement.
    I must hit the accelerator lightly to avoid the stalling. He will be working on it next week to check out the problem.
    It ran great for the last 14 years. RICH

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