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Fouling out #7 repeatedly...

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by PhoenixZorn, Jun 4, 2006.

  1. PhoenixZorn

    PhoenixZorn 1/2 ton status

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    A bit of history first... My 1970 K5 has an original sbc350, th350 and 3.08 gearing with 33" BFG M/Ts. Since I bought it it has run somewhat rough, occasionally running like it should, but most of the time, misfiring on #7...

    So I just completed a seudo-tune up on the k5 on Friday. The tune up consited of plugs and wires, and air filter and fuel filter a couple months ago. It drove like a brand new truck for about 3 hours... Engine was peppy, it spun the tires on takeoff, and it got fair to middlin mileage on the freeway compare to other times I've driven it. I got to my parent's house, dropped off the kid and headed over to a buddy's house because he'd never seen it with the top off. It drives fine all the way there, and I go inside.

    A few hours later, we decide to go cruisin', cus it's Friday, and we ain't got **** to do... The truck starts rough again, and I think "eh, it's chilly, it'll warm up and clear out.." but no dice... I pull over on the side of the road, lift the hood, and start feeling around on the distibutor... I go clockwise, starting at #1, and feel to make sure all the wires are tight... It's all good until I get to #7, and get wholloped by the distibutor... The plug wire was off the post. I replace it, and it drives fine for another 5 minutes, then it starts coughing and sputtering again when I "give her the berries..."

    I pull over again and check everything out... nothing detached, all the plugs are tight, etc... I drive my buddy home, and head over to another friend's house to visit, as he's never even seen my truck and I've had it for 8 months... and the top is off, so it looks cherry. It dogs all the way to his house, and I take him for a drive. He agrees that there is something wrong, and I park the truck for a little while.

    ***Intermission - Enter Playstation 2 and Guitar Hero***

    I drive home to my parent's house, and it still does the same damn thing, dogging all the way home... I juice it, and the engine cuts out until I let the pedal go... I go to sleep.

    Now to Saturday... I get up at noon, go wash the truck and drive over to my buddy's car show. The truck continues to dog me all the way there, and isn't all that impressive as a classic truck because it's not running right. I jump up in the engine bay, check all the plug wires again, and everyhting is fine... Then I realize that #7 (because it's light out now) is the wire that I didn't replace because the one in the new package was broken in the box. So I go to 3 parts stores looking for a single plug wire, and no one has them...

    Today arrives without a hitch, other than me worrying about why my truck isn't working right... then it dawns on me that the #7 wire was disconnected for at least 5 minutes, and it would only take a few seconds of being soaked with gas to foul out the plug... I'm on the freeway, and forget to stop at the parts store when I get home because I was carrying stuff for my wife from Home Depot... Anyway, long story short, I think the wire is the cause of #7 fouling out, and I can't think of anything else that would cause it... so if you guys have any other ideas, they'd be appreciated.
     
  2. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Hard to say I have had cars do that and it ruined the terminal where the plug came off of. It is fuel fouling and not oil fouling right. If so I say replace the cap and rotor again. If only one cylinder is doing this its gotta be either the cap rotor plug or wire. Or about a thousand other things but that is my vote and I have no idea how to test the cap
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    I've had similar problems with crappy performance.

    Ultimately I traced it back to a skanky cap/rotor on my MSD billet dizzy....keep in mind, they were NOT that old either.

    The first time I solved it, the cap had burned through the center electrode due to excessive resistance on one plug wire (have you ohm'ed your wires yet) the MSD box was cranking up the voltage to overcome the bad wire and ended up burning up the cap conductors. I ended up building all new MSD wires (and checked EVERY one for resistance, none were more than ~130ohms)

    The second time, I found another skanky cap and rotor and replaced them both. The truck immediately ran perfectly again. MSD caps don't seem to last that long (like maybe 1 year?)


    As a side note: I've noticed that the MSD caps I've gotten most recently now include a small "breather" with vent cap....presumably to allow moisture and ozone to escape from the cap as the engine runs and warms up???? Perhaps MSD got a lot of complaints about their cap/rotor longevity??
     
  4. PhoenixZorn

    PhoenixZorn 1/2 ton status

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    Well... I still ahve Points Ignition, so I'm looking for a good HEI conversion or full setup... I'm going to take the truck to the shop when the weather clears (its raining again) and have one of my advanced techs do compression checks, voltage checks, etc... I could do most of it myself, but I don't trust myself with diagnosis, only with the actual repair...
     
  5. Hossbaby50

    Hossbaby50 3/4 ton status

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    In my experience with my truck (several motors) they all have been prone to fouling the back plugs (closest to the firewall) first. That is where my SBC's have started to leak oil into the cylinders and foul out the plugs. Check your timing. Open the gap on the spark plugs a little. Change the cap, rotor, points, condensor. Make sure to use good plugs like AC Delco or something like that. Don't use cheap crappy autolites or champions.

    Harley
     
  6. mouse

    mouse 1/2 ton status

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    Use a good quality set of points as well, and use a dwell meter to adjust.
     
  7. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    For some strange reason I kept my points on for a while, :doah:Get a HEI off of E bay I think mine was 50 bucks. Really didn't make a huge difference in the performance of my truck cause I kept up on the points but now I don't have to check my points and adjust them. It is way nicer
     
  8. Hossbaby50

    Hossbaby50 3/4 ton status

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    I have points in my Jeep CJ5. I personally will never switch it to HEI. Points are way to easy to deal with and way to cheap to deal with.

    Get the best points you can find like mentioned. My Jeep had problems with cheap points. It would burn them out in nothing flat. The best points that Napa carried were only like $12. I love that Jeep and how simple it is to keep running. I do love the TPI I put on my K5 too but that can give you fits. I have spent more then a few nights up late pissed off trying to figure out WTF is wrong with the HEI and TPI in my K5.

    The Jeep just made life easy. If it wouldn't start I popped the cap and used the remote starter to spin the motor over and see if the points are opening. If they weren't I adjusted them till they opened and bang it started. If it ran rough I pulled the passengers front plug and cleaned the oil fouling and bang it ran great.

    Life with points is way to easy for me to pass up. If I didn't offroad my K5 at some heavy angles I would honestly think about giving up my HEI for points.

    Harley
     
  9. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Exactly why I got HEI. Although I kept the points disty as a spare
     
  10. Hossbaby50

    Hossbaby50 3/4 ton status

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    I have had alot more problems with my HEI on my K5 then I have had with the points on my Jeep. And when the problem arrises with the points it is alot easier to fix quick and diagnose.

    I had a bad pickup coil in my K5 that would kill the motor every 40 miles while I was on a 200 mile roadtrip. The pickup coil would get hot and the motor would die. I would have to sit there and wait for the pickup to cool down enough to have it fire up again and drive till it quite again. Let me tell you how much fun it is trying to diagnose and fix that problem on I-10 with vehicles doing 80mph past you as you are working on a hot motor when it is 100* outside. I changed the ignition coil and module out on the side of the road. Once those things didn't fix the problem I knew it was the pickup coil. There was no way I was going to pull the whole disty out on the side of the road so I just would keep driving till it would die and sit there till it started.

    I had a ignition coil that did the same thing. It would get hot and die. Then once the coil cooled down it would start again like nothing ever happened.

    I have had repeated problems with modules in the TPI.

    It may just be me but I was way happier with the points on my Jeep then the HEI in my K5. If the above problems would have happened in my Jeep I could have fixed the problem in 10 minutes with a screwdriver and been on my way and never looked back.

    Harley
     
  11. 3 on the tree

    3 on the tree 1/2 ton status

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    I put a HEI dist in my 70, and immediately could feel the improvement. Course, I replace everything inside the HEI before I installed it. Also did a curve kit and adj vac advance. If I ever move to a lower elevation, I will have to re-tune everything, but getting a vehicle to run right at 8000 ft is not an easy task.
     

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