OHMs at the coil pickup in the distributor

[old yellow 78]

Can someone please tell me what the OHM reading should be at the coil pickup in the distributor on the Super Slant Six with two barrel carb and four speed? I get a reading of only 285 and I was told it should be between 1000 - 1200. Amazingly, the factory manuals don't list it! 285 seems way too low. Thoughts?

 

[Aspen500]

I don't think there really is a spec for resistance on those. Went out and measured a couple known good ones I have and they were both 285 ohms. Since you also got 285, it must be the normal resistance.

I run into this all the time at work and finding a resistance value for things like hall effect sensors is all but impossible. Should it be 300 ohms, 11K ohms, 3-4 Mega ohms, what? Pretty much have to measure known good ones and compare. Would it be so hard for them to publish the normal resistance range in the service manual? I mean, seriously.

 

[volare 1977]

this guy says 350 to 550 Dave's Place - Chrysler Electronic Ignition System Test

 

[old yellow 78]

Thanks to both of you! The one that came out was only about 100. Put the new one in, and it was only 285. I was thinking that something else was still messed up. OY just isn't running right. Doesn't seem to have the power it should, and it bucks at times under normal driving/cruising load, and was stalling backing up and pulling forward. The new coil pick up seems to have stopped the stalling, but the occasional bucking under light load while cruising and only "meh" power tells me something else is still not right. Just rebuilt the carb, checked the fuel pump, drained the gas tank and that seemed fine. Not sure what else might be going on if the coil pickup is good. Hummm.

 

[Aspen500]

Might want to substitute a different coil (ignition coil, not pick-up coil). A weak coil can cause bucking, loss of power, etc. Might not be the problem but it's one thing to eliminate as a problem. I had problems similar on my old '81 D150 and also Dakota shortly after buying each of them. Slight miss on light loads, light accel and slight hesitation on throttle tip-in. On both of them, it turned out to be the almost brand new Champion plugs.

You've probably done this already but, make sure the air gap between the reluctor and pick up is .006". You need a brass (non magnetic) feeler gauge to be accurate. Too wide a gap will give a weak signal to the ignition module.

 

[Oldiron440]

This thing has been sitting how long, so the fuel is fresh right?

 

[old yellow 78]

Might want to substitute a different coil (ignition coil, not pick-up coil).

Ah! That's a good idea. I don't think I've ever replaced that.

turned out to be the almost brand new Champion plugs

I'm pretty sure I changed out the plugs last year, but don't remember what brand they were. Worth a try.

make sure the air gap between the reluctor and pick up is .006

Yep, did it. Factory manual says to set them for .006, tighten it up, and then the gap will be set at .008. I guess tightening the screw makes the .002 difference.

fuel is fresh right?

Yep! Drained the tank, cleared out the lines, fresh gas.

 

[Aspen500]

Don't mean to sound like I'm ragging on Champion plugs but, every car I've owned with Champions never ran quite right until swapping them for a different brand like Motorcraft or AC Delco. Maybe I'm just unlucky and got the bad ones At work, I've fixed a lot of vehicles for a driveabilty concern by taking out almost brand new Champion's and installing a different brand.

I had another thought (yeah I know, look out!). The ignition module itself can cause all sorts of driveabilty problems similar to what you describe, misfiring, stalling, bucking, etc. Another part there's really no way to test other than, as the service manuals frequently say, "substitute known good part and retest".

 

[old yellow 78]

I was wrong. The OHM reading on the NEW pickup coil is 385, not 285, and it does run much better now, but OY still has that intermittent, annoying "bucking" when just crusing along in either 3rd or 4th gear. My friend says the Chrysler factory manual lists OHMs should be "between 100 to 900". Well, if that's the case, then even the old pickup coil in the distributor should have been fine - BUT replacing it, did seem to make a significant difference.
I'm going to replace the ignition coil next as that seems to be a likely culprit - thank you Aspen 500 for that suggestion!
The plugs are Champions which were new last year. I never had a problem with them before, but who knows.
As for the ignition module, I see that it was replaced at some point in the past with a "Big A" brand. Not sure why someone would have had to replace that with only 27,000 miles on it when I bought it. I wonder if that could be messed up?
I'm doing a lot of work to OY right now, and will update when I get a chance, but this problem with what seems to be ignition is mystifying. The wonderful Super Six is such a simple engine, that I am frustrated that I can't seem to solve this problem, even with my limited mechanical skills. Any help or insights would be greatly appreciated!

 

[volare 1977]

Maybe not your problem but the new ignition modules sold now I heard are junk compared to the OE ones.

 

[Oldiron440]

Maybe not your problem but the new ignition modules sold now I heard are junk compared to the OE ones.

I agree with this.

 

[Aspen500]

If at all humanly possible, try to find an Mopar ECU, either new or used. As mentioned, the made in China one's sold at the parts stores are complete crap.

I feel your frustration. More than once, I've had to fight and fight to find the problem on something simple. You keep telling yourself, "it can't be that difficult". Then when you do find the cure, it turns out to be so simple you don't know how you could have possibly missed it because then, it seems so obvious.

We'll all get through this!

 

[Darth-Car]

I had a similar problem years ago with a blue oval mobile that I owned. The car had always run well, and then the occasional bucking started, and the lack luster performance. The short version of the story was after hitting all of the previously mentioned items I put on a new distributor cap, and the problem was solved! After a very close inspection with a magnifying lens I found a small, small crack around the #4 spark plug tower. After the change, all was right with the world again.

 

[old yellow 78]

If at all humanly possible, try to find an Mopar ECU, either new or used. As mentioned, the made in China one's sold at the parts stores are complete crap.

I feel your frustration. More than once, I've had to fight and fight to find the problem on something simple. You keep telling yourself, "it can't be that difficult". Then when you do find the cure, it turns out to be so simple you don't know how you could have possibly missed it because then, it seems so obvious.

We'll all get through this!

Thanks Aspen 500! I have no formal training in auto mechanics, just what my father taught me (he was a Chevy/Buick and VW mechanic) and that which I have learned on my own. I have owned many /6's, (mostly one barrels) and never encountered this particular problem before. The Super Six automatic that was in my '79 Volare wagon was as quick as a 318 and I never had any problems with it at all. I might have an old Mopar ECU sitting around in the garage somewhere, but... where? Used to be able to just go to the local yard and get something like that easily, but not anymore!

 

[old yellow 78]

I put on a new distributor cap, and the problem was solved! After a very close inspection with a magnifying lens I found a small, small crack around the #4 spark plug tower. After the change, all was right with the world again.

Another excellent idea Darth-Car! I am pretty sure that I replaced the distributor cap last year also, but I'm not certain. It's certainly worth a look/see. Might have cracked since then I suppose.

 

[Oldiron440]

One thing that needs to be remembered is that you replaced a part with a new one 500 miles ago doesn't mean the part is good. The quality of all aftermarket products is always in question. It's got so bad even the name brand parts are not the same quality of years gone by.
Don't assume that the parts you replaced last year are good just because you have replaced them.

 

[old yellow 78]

Any ideas BudW?

 

[Aspen500]

Won't help with your car, I was just reminded of something one of the auto instructors at the local tech college said to us in 1983 when I was a student, "new just means new, it doesn't necessarily mean good". After 35 years as an auto tech, I've discovered he was right.

 

[old yellow 78]

Ok, so now I have my neighbor working on OY.

He is an 84 year old life-long mechanic who seems more like 63 years old. He's a Buick man, and has restored several including a '63 Riviera which he just sold for $$$, but still keeps his favorite, a '63 LeSabre coupe that he has restored to PERFECT like new condition. He got my '50 Chief running smooth as silk, so maybe he can purge the gremlin(s) from OY.

I also decided to have him replace the rear springs and hardware along with all four shocks on OY as he is much more set up to do it with a lift and all his tools (and experience). I bought KYB Gas-Assist shocks all the way around, and NEW leaf springs and hardware from "Springs & Things" (thanks Duke5A for the recommendation):
Budget Suspension Rebuild
So, we will see.

 

[Aspen500]

Great people at Spring's and Things.

About the KYB's. Turns out they're stiffer than a 18 year old, well you know. Had them on my car until recently, and now switched to Monroe OESpectrum's. Much nicer ride.