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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Issue is not resistor plugs, I've run them for years on L78 would suspect coil is issue. Just another thought - what condition is distributor shaft and bushings in ? a small amount of wobble or up and down play can cause issues (even a new one). Be sure mechanical advance is not sticking or springs have popped off/to strong/too weak. Last of all timing chain slop ? Sounds like coil IMOComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Y'all are going to think I'm crazy but here goes. I had a great conversation with Dave Fiedler. However, Dave said his expertise is with the original TI systems, not reproductions. In any case he did not have an original GM coil for sale. So I called Holley and asked if they had an MSD substitute coil for the TI system. They referred me to MSD model 8222. They said this coil delivers about 35 Kv (Dave said the Delco coil should deliver about 32 Kv) and the pole to pole resistance was 0.7 ohms (very close to the Delco coil).
Four times I swapped the repro coil and the MSD coil. Each time the MSD coil would not give a hint of starting the car. The repro coil started the car nearly immediately. Here's the bizarre part. I removed the #3 spark plug and connected it to a lawn mower plug with a 0.035 in gap. Both the repro and MSD coils delivered a spark when cranking the engine and the plug grounded to the exhaust manifold. This seems to confirm Rich's experience with the aftermarket (MSD and UC12) coils.
As to Carl's questions, the engine only has 700 miles so the timing chain should be tight. There is up/down play in the distributor shaft but one of the coils works, at least until it gets warm. The advance springs are in place and the weights move freely.
I have the white wire connected to the + pole for all (repro, MSD and UC12) coils. Is this right? I'm grasping. Thanks for hanging with me.Comment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Scott,
Very strange.
Yes, white to Coil+. Coil- is hard ground from the TI Module case/radiator support.
I'm wondering if your K&B circuit board has some odd fault behavior going on. Very rarely have I seen faults with them, but it did happen to me on a few occasions. One was a subtle unexplainable ignition miss issue on a '65 fuelie at a particular RPM. We verified by swapping in a Delco module. K&B did a warranty swap of the suspect, and the replacement was perfect and corrected the miss.
Another odd issue, no start condition on another K&B board. A '67 L71. This however turned out to be a bad ground on the module circuit board to the case, caused by the 3 mount screws inside the case being too long. The K&B is a bit thinner, and the original screws holding the Delco board bottomed out in the case leaving the K&B board loose.... intermittent ground. Shorter screws solved that.
In your situation, you may have some unusual combination of electronic incompatibility going on that is hiding the true fault. One thing I've learned over the years is that often, a no start is sometimes caused by low cranking input voltage to the system. TI is very sensitive. Solenoid "R" provides full battery voltage to the PU coil and TI module circuit board. A dirty Solenoid contactor or a marginal battery can be a problem on no start. This is often recognized by getting a single spark when cranking and it'll yield a singleone spark going to RUN from CRANK.
All this info doesn't really help the cause in your case, so.....
I have a proposition. I think I can get my hands on a used 207 a friend nearby owes me. I also have, in my possession, a loose M&H circuit board, along with a original Delco module assembly, both functional as I've used them over the years as spares and bench testing experiments.
I will send you all of this hardware this week to help diagnose your problem. The 207 should be all you need, but I'll send it all just in case we need it to diagnose a subtle issue with your existing hardware.
Today I'll check with my friend and try to get the 207 in my hands. If I do I'll box it all up and send it to you tomorrow or asap. Not sure where you are, so PM me your info. Lets see if we can get you going on a normal ride soon.
If any one of these items solves your problem, lets say you'll be on a loaner program until you find a replacement for your original fault item. Then you can send me my stuff back. Don't worry about USPS reimbursements or anything yet, we can settle up on that later.
RichComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Scott, Richard
Regarding the wires to the coil for a TI system, my 1965 AIM references that the white wire goes to coil ( - ) and the black wire goes coil ( + ). This is found on pages E299, E317, and E376 which all show good illustrations of the black and white wire termination. There is also a Restorer article from summer 2008 prepared by Randy Merzdorf about troubleshooting TI systems in which he states that the amplifier switches the positive terminal whereas a point ignition switches the negative terminal. His primary source of reference for his article was Dave Fielder. Not sure if all this applies as well to repro or aftermarket coils currently available.
RayComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Ray, 66,67 is reversed from 64,65. White to Coil+ on Scott's 66.
RichComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Rich,
I was not aware of that change in wire configuration for '66 & 67. Thanks for the update.
RayComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Thank you Ray. If the AIM says flipping the polarity then at least I shouldn't destroy anything in the attempt. Unfortunately flipping the polarity today didn't help. Interesting article from Mr. Merzdorf. He lists some amp issues such voltage sensitivity that I will discuss with K&B. Surprisingly he didn't mention the ignition coil.Comment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Scott, been following along.
If Richard has trouble locating a coil or TI module, your welcome to try mine out of my 66- L36. Worked fine when I tore down the engine and I probably will not be needing them for another 6 months as the car is just coming together. Let me know.
Still haven't seen if you have confirmed the no spark situation when the engine dies. Maybe I missed it.--Joe SComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Ray, Here are the 2 diagrams showing the differences.
As you see on the earlier 64-65 configuration,, the ground path from the core support/module case passes through the white resistor wire to Coil-. Coil+sourced from the Amp output, Black wire.
For 66+, the resistor wire path goes to Coil+. Coil- is hard grounded. In fact, for 66+, a diagnostic is to jumper a wire from Coil- to engine hard ground to eliminate a defective TI harness ground path.
Rich
64-65
64-65diagram.gif
66-67+
66-71diagram.gifComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Joe, I got so engrossed in the coil swap that I forgot to confirm 'no spark' last time the car would not start with the repro coil. Rich is sending me a coil to try so I'm going to wait for that to arrive. Last time (last week) it took over an hour to get the car up the driveway.Comment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Scott , while your waiting for the coil to come in , I would pull all the sparks plugs out and clean them before trying the new coil to restart , also confirm your choke settingComment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
I got a loaner genuine GM 231 coil and enjoyed a 10 mile trouble free drive!!! The first in several months.
For the record I talked to K&B before the GM coil arrived. The person I spoke to said an aftermarket coil was not the same as a repro TI coil. However, when I said my aftermarket coil had 0.7 ohms resistance he proceeded to question other parts of the system. Long story short, he tried his best to help but didn't have any revelations.
In any case the issue appears to be solved. Anybody know of a genuine GM TI coil for sale? I saw some at Heartbeat City. They were very proud of their coils. Perhaps $500+ is fair market value but I would like to get away with less. Anyway I thank everyone again for contributing, especially lending the coil. I've been told that only a small percentage of the NCRS members use the Discussion Board. That baffles me. Hopefully, I can pay this forward to someone else.Comment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Glad you got it figured out Scott , the coil does amazing crazy things 👍Comment
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Re: L72 Dies at Idle - Magnetic Pickup Coil Resistance
Scott, Very glad the test coil proved the repro coil was the actual fault. Tearing into the distributor to swap the PU Coil as a
Diagnostic exercise is not easy.
I'll be on the lookout for a Delco 207 for you too.
You probably spoke to fellow member Ken Anderson who owns K&B. I still have 2 repro 263's that failed identically to your scenario. Unfortunately, it was on the same K66 car, '67 L71. This added a negative level of diagnostic troubleshooting I'd never want to experience ever again.
RichComment
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