SOLVED- Ignition issues! was: 1967 S800 4cylinder not running right- ideas?

Discussion in 'General IH Tech' started by Scoutcamper, Jul 28, 2019.


  1. Scoutcamper

    Scoutcamper Farmall Cub

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    I thought I used the correct choice for the Delco from the manual, but now you've got me second guessing. I certainly could have looked at the Holley number, since I'd just been working Holley carb stuff. Probably gonna have to wait until the weekend to find out, work has been bonkers lately.

    -Josh
     
  2. Scoutcamper

    Scoutcamper Farmall Cub

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    It's been a pain to find time to work on Wilma, but I'm getting back on it. Points look good and gap is right- I did use the Delco numbers but they are very close / overlap the Holley numbers- but I have not had it running well enough to play with dwell. I used a point file to set gap, so shouldn't be any issues with oxidation or pitting. Correct me if I'm wrong, but if I set the gap correctly I should be pretty darn close on dwell anyway.Well enough to get it running / idling, anyway.

    Timing and vac advance checked out good, looks like the spark is dropping out randomly.
    I didn't measure dizzy end play but it felt nice and tight. Advance weights don't seem to be binding, and the vac advance moves the plate.
    I'm putting my money on bad new condenser and / or bad brand new bad coil.
    I'm basing this on the observation that when I was checking timing the light failed to flash consistently in conjunction with when it seemed to be cutting out. Coil was also getting pretty hot.

    Got a new coil and the condenser is on the way. I'm planning on replacing both at once.

    Anybody know if a bad coil will burn out the condenser?

    Pretty sure a bad condenser will fry a coil if I remember ... Wonder if I had a self-perpetuating problem going? Replace condenser but bad coil takes it out, replace coil but bad condenser takes it out, and repeat...

    -Josh
     
  3. walkersscout

    walkersscout High Wheeler

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    Not to discourage you, but I had the same issue with my 67. Not sure how I arrived at the decision, as its been many years, but I pulled tge head off. It is a contour piston motor. I had 4 cracks in the head. One in each cylinder from one valve through the sparkplug hole and to the other valve. Huge cracks, no need to mag it to find them. A compression test and a leak down test would likely confirm this.
     
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  4. Scoutcamper

    Scoutcamper Farmall Cub

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    Already ran compression, everything looked good. 115 - 125psi in all 4 cylinders. It doesn't seem to be burning oil and the coolant looks good. I might run a leakdown test if the new coil and condenser don't fix things, but if it's getting compression it seems like there shouldn't be any internal engine problems that would keep it from running. I don't feel like I'm quite to the stage of pulling the motor apart yet. There's also a borescope at work I could possibly borrow to inspect the cylinders, or I could pick one up at Harbor Freight.

    -Josh
     
  5. Don B

    Don B Farmall Cub

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    Hmmm, this is curious. So you have spark, new coil, new wires, new correctly gaped plugs, condenser. The plugs put out a good spark. The timing has been checked (you can check the static timing well with a light bulb circuit at the distributor at the no 1 position and checking the timing marks.) So the ignition system appears to be good. You don't have any vacuum leaks and the carburator settings are good and you have good fuel flow. The fuel lines are not plugged. The gas you have is, I would guess not suspect (does happen!) Compression is good. I would do this...check the ignition parts installed-cap..I've seen ones that were NG from the get go even missing contact points. Points should be checked for continuity when closed recheck gap. Plug wires..had a lot of problems with these. RechecK that they are all making sold contact...I have seen them "light up" in the dark when they are NG! Make sure the fuel is being pumped to the carb and that your getting gas flowing out the carb to the intake manifold. For sure recheck all hoses, pvc etc to look for a massive vacuum leak.

    Thats about all I can suggest off the top of my head. I have had all of the above go wrong in past cars.
     
  6. Scoutcamper

    Scoutcamper Farmall Cub

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    Almost. I previously THOUGHT that I had good spark.

    When I pulled the coil wire or spark plug wire and cranked it under the hood to check, I got a nice fat spark.
    What I've seen the past couple of tries at it is that it will initially start up and try to idle for a bit, then die. As I continue to try to get it to start it will seem to taper down until it will turn over with the starter but hardly fire at all.
    What I observed when I tried to check timing is that the timing light would start to miss or just flicker, corresponding to when the motor stumbled and / or died.
    Also observed was that the coil was getting hot to the touch very quickly.

    My suspicion is that either my brand new coil was bad right out of the box, or that the condenser is bad and fried it pretty quick.
    I'm going to replace the condenser and the coil together and see if my problems magically go away.
    I don't want to test the "bad condenser is frying coils" theory since a coil is $23 and a condenser is like $4.

    I'll let you guys know how it works out.

    -Josh
     
  7. Don B

    Don B Farmall Cub

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    I have had a lot of crap coils in the last 10 years or so. Even expensive new ones can be junk. One thing I like is to shake them before you buy to see how much coolant oil they put in. The more oil the better! You can hear it when you shake it. The oil cools the coil. No magic for the condenser though!
     
  8. Don B

    Don B Farmall Cub

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    Something else which just popped into the old head is feed wires to your ignition parts. Wires which have a hard end that is put on a post can break inside the insulation so they look ok but have frayed to breaking or almost breaking. This is a tough one to see but wriggling the wire with both hands to see the movement can sometimes show this fault. Using a multimeter may not work as the wire frayed section makes intermittent contact as you move it. Jumping the wire with a good one is one way to test this. Not real common problem but it’s a possibility.
     
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  9. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    Let's talk about your resistive feed to the coil positive terminal. Is it still intact? Has the length been modified? It should be much longer than necessary to span the run distance. That excess length, along with the coil's primary resistance is what combines to protect the points and keep the coil from overheating. If you can get your coil to a room temperature state, you should measure the primary resistance across the polar terminals with no wires connected and also the secondary resistance between a pole and the center terminal. The first number will be quite small, while the second will be quite large, so set scale accordingly. Post your results here.
     
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  10. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    You say you went with a UC12 coil. That coil has a primary resistance of 1.5 ohms, which is great for a V8 engine with points and proper ballast to get the total resistance up to roughly 3.3 ohms. Your I-4 with breaker points needs more resistance than that. Your coil should have a primary resistance of 3 ohms. Then the resistive feed should add another 1.8 ohms, for a total of roughly 4.8 ohms. So if your second new coil also has a 1.5 ohm primary resistance, then I expect you will have the same issues. Rock Auto isn't always up on these nuances. They list a coil for your engine that actually isn't correct. Not enough primary or internal resistance.
     
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  11. Scoutcamper

    Scoutcamper Farmall Cub

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    My understanding was that the resistive portion was under the dash, and that the wire on the engine side of the bulkhead connector is just standard 18(?) awg wire-harness wire.
    I was seeing around 6.5 - 7V to the positive lug of the coil, so I was making the leap that the resistive wire was working correctly.

    I have no problem setting up a 12v feed right off the battery and testing with an old super-coil or such, if it would be of value in troubleshooting.

    -Josh
     
  12. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    Yeah, on the early Scouts I believe that wire is under the dash. I think my follow up post regarding the coil primary resistance may be the more pertinent issue to resolve anyway.
     
  13. Scoutcamper

    Scoutcamper Farmall Cub

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    It will probably be a while before I can find time to do it, but I'll definitely check these numbers when I have a chance to wrench on it.

    I'm guessing I'll want to baseline the measures before starting, then check again when the idle quality is shot after a few attempts at getting it running?

    Do you happen to have a P/N for a "more correct" coil?

    -Josh
     
  14. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    Try a UC 15T. The room temp baseline is generally good enough. The reason it's acting up is the coil is overheating. That doesn't mean it was a bad coil to begin with, although it might be getting there now. It just wasn't the right coil for your engine.
     
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  15. Scoutcamper

    Scoutcamper Farmall Cub

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    OK, measuring with my trusty Harbor Freight multimeter I got:

    New Coil, UC12T, the one I have been trying to run on:
    5.4 Ohm primary resistance, 8.74 K Ohm secondary

    Old Coil, possibly original? The one I replaced when I put on my tune-up parts after the issue started:
    2.2 Ohm primary resistance, 9.17 K Ohm secondary

    These numbers were taken at about 90 degrees ambient temp, and were repeatable.

    -Josh
     
  16. Scoutcamper

    Scoutcamper Farmall Cub

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    Another "Interesting" observation:

    One of the issues I've had was bad "PO Special" wiring, including the feed to the positive terminal at the coil. I built a new harness for the Coolant Temp / Coil + / Oil Pressure wires to replace the one I thought was problematic.

    The reason I came to this conclusion was that I could jiggle the harness and it seemed to have a direct effect on the rough running. After replacing the harness it did not seem to effect performance by moving the new wires around.

    I validated this on the old harness, or thought I did, by measuring a continuity between all 3 wires if I moved them around.

    It occurred to me that I did not check the "PO Special" bus bar these wires were installed to. I unhooked my new harness and tested between the terminals on the bus bar.

    I am seeing a very consistent 134 - 137 Ohm resistance between any 2 of the terminals- Coil, Coolant, and Oil Pressure.

    This test was done with the battery unhooked.

    Am I just reading the resistance from the ammeter / ignition switch feed? Can somebody repeat this check on a properly wired 800 and let me know what you find?

    Here's the PO special wiring for reference. The green wire with a fork terminal in the foreground feeds a relay for the electric fuel pump from the same terminal that feeds the coil positive. I have not moved it, since it was running in this setup. You can see why I suspected this might be an issue.

    -Josh

    Harness Problems.jpg
    20181101_075927.jpg
     
  17. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    That's not good out of the UC12T. It should be 1.5 ohm at 70F. I'd expect a little higher at 90F, maybe as much as 1.8. The older one at 2.2 ohm is closer to what a UC12T or equivalent should be. Still not right for your engine.
     
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  18. scoutboy74

    scoutboy74 Lives in an IH Dealership

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    My recommendation is to get your feed to the coil as isolated and direct as possible between the IGN switch and the coil. Get it off that buss bar. Make a direct connection with the resistor wire under the dash and then straight out to the coil terminal. Don't pass go, Don't collect $200. Also, the wires terminating at the coolant temp and oil pressure senders shouldn't be in contact with B+ voltage. Those wires should also be a direct run between the respective senders and their respective gauges. The other side of the gauges get the switched voltage, which is all behind the dash. No reason whatsoever for it to come out into the engine bay at all.
     
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  19. Scoutcamper

    Scoutcamper Farmall Cub

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    I'm guessing it's going to be time for a full replacement harness if I start tearing into it. I've got a few more tricks I want to try to get it back on the road before I go that far, but this mess certainly is pushing me in that general direction.

    Agreed on the direct wire for the coil to isolate things. I was just curious if there was a functional reason I should be seeing that continuity / resistance across the coil +, coolant sensor, and oil pressure sensor.

    -Josh
     
  20. Don B

    Don B Farmall Cub

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    Nice melted bulkhead connector. I think when I redo my harness I'll forgo these and just leave enough wire so the dash can come forward a bit.
     

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