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Technical Motor hesitating on acceleration

Discussion in 'The Hokey Ass Message Board' started by MoparJoel, Jun 28, 2014.

  1. MoparJoel
    Joined: May 21, 2012
    Posts: 860


    Hi, I usually can solve most mechanical problems but have reached a point where I'm just getting tired and am needing some suggestions to make some light bulbs go off in my head. So here goes….

    I have a 1957 D100 with a 1978 360 four barrel that was my daily driver. Over a year ago i was deployed to South Korea, and the plan was for the wife to start the truck up very couple weeks or so until i got back, well that didn't work out to well, since she ran it out of fuel after about a month. so for about a year the truck sat in the driveway until my return. I tried getting it started but it was not getting spark. So I traced it down to a bad coil (don't know why it failed from sitting, but it did) after replacing the coil it fired right up with some new gas.

    Now after about a 15 minute drive the truck starts acting like its going to stall on acceleration up to about flooring the pedal then it acts fine, it even back fires. when under 15 minute drive when shut off and started back up it does it worse. so my conclusion is heat is the issue along with a restriction. The truck acts normal at idle and full throttle but not in-between.

    So I rebuilt the 600 cfm Edelbrock a week ago thinking it would fix the issue along with changing out the fuel filter also moved the fuel line further from the block/headers but it did nothing. The whole system tank, lines, pump, carb are all under 5 years old. starting to maybe think its electrical. But i can't see it being affected by heat. The truck had no previous issues with vapor locking or anything close to this problem.
    Could the new coil be affected by heat and cause an intermittent problem? I dont think so but right now I'm really scratching my head.

    Heres the specs:
    360 engine with electronic mopar ignition/ distributor. metal lines running from the tank to the filter then rubber fuel hose to the mechanical fuel pump. and then from there rubber fuel hose up to the 1406 Edelbrock 600 4 barrel. 223390_221428354534545_3535786_n.jpg
    Last edited: Jun 28, 2014
  2. missysdad1
    Joined: Dec 9, 2008
    Posts: 3,022


    If nothing else has changed I'd go back through the carburetor in search of the little bit of crud that I missed the first time. It doesn't take much. Good luck.
  3. What about your mechanical and vacuum advances? weights sticking, vacuum advance diaphram not holding. Old gasoline can cause all sorts of problems, you may have to flush out the tank.
  4. Sounds like a lean condition to me. I'm not a fan of edel carbs. Do you have a holley you could try.

  5. MoparJoel
    Joined: May 21, 2012
    Posts: 860


    I dont really know too much about the advances. but I'm curious how the heat would affect the vacuum advance?

    sorry nope no other 4 barrel carb available.
  6. stimpy
    Joined: Apr 16, 2006
    Posts: 3,547


    check your coil to see if its hooked to the right sides , sounds like your wife left the key on without the motor running for a while that kills coils ( cooks them ) also check the ballast resistor ( change it out with a known good one ) as I have had problems with them if they got too hot .
  7. goldenidolcustoms
    Joined: Jun 13, 2010
    Posts: 252

    from Pa.

    Did you check and make sure you had a good spray in the carb when you depress the throttle?

    If all is fine try changing the coil wire.I had a similer problem and it turned out to be my new coil wirw was bad.
  8. MoparJoel
    Joined: May 21, 2012
    Posts: 860


    its hooked up right. the Ballast is something I have thought about, but I've never seen and on and off problem, they seam to work or they just dont. thanks for the advice!

    i took my multimeter to the coil wire and it checks good and the spray seams fine but you know its hard to tell could be off by a little and look fine.

    SO…. for the last hour I decided to really get some hard evidence on the issue by driving the pisss out of it and get it nice and hot, mess with the set screws and see where and when exactly it happens.

    so It starts the issue at almost exactly 200 degrees. Which the truck under normal driving conditions in the summer here in the desert runs around 210. So as soon as the problem started i pulled over and started adjusting my idle mixture screw on the front, and that didn't seam to make any difference at all. then returning them to where they were. I adjusted the fast idle screw up. and the problem completely disappeared. So now I'm really scratching my head because I was sure that wouldn't change anything especially at higher RPMS. does anyone know why this might have been the problem. Im going to do some more testing now (cooling it down and drive the piss out of her again) thanks for all your guys advice.

    I just hope the problem stays gone, might try to go to a car show tonight about a half hour away so that should be a good test.
  9. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    from Wisconsin

    When adjusting the idle mixture screws doesn't change anything, you have a carburetor problem. Idle mixture probably won't help throttle response but it indicates that there is a problem somewhere in the carb or possibly a vacuum leak elsewhere.
  10. MoparJoel
    Joined: May 21, 2012
    Posts: 860


    The problem still exist and I believe the fuel addition just masked the problem…...So after being really busy lately i tore into my truck today some more. I got one of those bulbs that plugs inline with your plug wires. so i started up the truck and it was hesitating right off the bat, at about 50% throttle. so I pugged my little spark indicator light in line. and clear as day the spark stopped when the motor hesitated. So now I think its time to look at the electrical system. Im going to try and zero out my timing first, which i haven't looked at in while. but i doubt that will be a fix for the issue. So I'm thinking its the distributor or ignition box. because i dont think the voltage regulator or ballast would create a intermittent problem……. any thoughts?
    Last edited: Jul 19, 2014
  11. MoparJoel
    Joined: May 21, 2012
    Posts: 860


    So I set the timing 2 degrees advanced, and problem continues…

    So heres the facts:
    1. spark cuts out at 50% acceleration
    2. I can drive normal (with minor hesitation) until engine warms up to 200 degrees (normal op-temp 210 here in the desert) then will not accelerate unless floored.
  12. enjenjo
    Joined: Mar 2, 2001
    Posts: 2,543

    from swanton oh

    Check the wires coming out of the distributor from the trigger. I have had them with internal breaks that would only show up when the advance was in the right position. Tug on the wires and see if there is any stretch in them, a sure sign.
  13. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 27,221

    Jalopy Joker

    enjenjo may be onto something. also, I have read here about the mounting of coils. this may not be accurate - with it being horizontal the oil cooling the coil does not cover all of the internal windings. So, it gets hot and malfunctions or even fails. the coil should be mounted upright. but, might need to be replaced already.
  14. Joel, the voltage regulator just controls charging and I've never seen a ballast resistor cause problems like that, in my experience they either work or they don't. If it's losing spark when it's hot I would start with another coil or another ecu if you have one, I've never had a distributer on a mopar do anything like that either but that doesn't mean it's not possible!

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  15. I've heard this as well, however the coils on mopars are mounted horizontal from the factory, maybe the replace ones don't like this though?

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  16. Im more than reasonably certain that the fast idle screw adjustment has nothing to do with your troubles. More than likely you caught the intemitrent problem . However you may have bumped or touched something else while fiddling and that was the cause of the correction. Re trace that and see if you bumped a harness or something.

    I'm curious to see how the spark tester shows spark dropping out at 50% throttle. Video maybe?

    If you believe this is a temp over time issue, look a things that may be heating up. Resistance from corrosion causes heat and at a predictable time span, grounds are quite troublesome and could have grown corrosion while it was sitting. Along with that is your ignition switch and don't forget the NSS. Check those for corrosion. Also plug wires do get hot and plug wires do wear out from the inside out.

    With heat, things move and anything critical can get off. Check your cap and coil for tracks or odd paterns and the pick up while you are in there. Give a check to the dizzy bushings too. The ECM might be screwing up too.

    Check your timing at 50% throttle (where it messes up) , see if that's steady. Try both vacuum connected and plugged.
  17. loudbang
    Joined: Jul 23, 2013
    Posts: 37,716


    Since it sat for so long have you checked for rodents chewing on your wires? Little buggers just love to eat the insulation and have caused problems like this.

    The other question is does it now have FRESH fuel?
  18. MoparJoel
    Joined: May 21, 2012
    Posts: 860


    I have gone through 3 full tanks since it sat and used fuel cleaner. I'm pretty sure now its not a fuel issue I replaced / rebuilt almost the whole system now. and after seeing the spark issue today I'm pretty sure I've got it down to electrical problem. I think i had a old mopar ignition box sitting in a crate somewhere in my garage now i just need to find it plug it in and see if that narrows down the problem. thats my plan of attack now. all the wires look great. and I put rat poison out before I left and my wife said that a cat living on top of the air filter housing so i think any vermin would be scared to go in there…lol… sucked cleaning all the hair off my engine too.
  19. porky55
    Joined: Aug 23, 2013
    Posts: 269


    Recently my buddys diplomat had the same problem. He docked around with the carb for a month thinking it had to be fuel. Then it died on the road and he got under the hood shaking everything and it started. Come to find out the wiring going to the ECU box was getting old and it wasn't working right. Went down to the dealer and bought a new harness for $20 and rewired it. No hard either. Works great for about a year now. He drives it 100 miles a day.

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