The Stovebolt Site Forums The Shop Area The Electrical Bay Continuity test?

I am tracking down a miss on my 216 with 12V conversion and used my induction timing light to check for power to each of my plugs, figuring if it lights, I have juice to the plug. I get no light on number four and no engine difference when I pull the plug wire. So I got out my multi meter to check the wire and got nothing. Then I checked a wire that did fire and again got nothing. My question is why is there no Ohm reading from a wire that functions? These are the carbon type plug wires and the meter works fine when I put the leads together, giving 0 resistance.

Hi Mike,
If one plug is not firing at all, you'll know that by the idle (assuming your idle speed is set correctly) and you'll know by driving it. You'll lack power and you'll feel a roughness while driving. Idling will be a jittery affair and at times your engine might seem like it is going to die (especially if your idle speed is around 525~550 rpm).

As for the multi-tester, if you're getting 0 ohms when you test each wire from end to end, that's what you want. Some meters will make a noise when the wire successfully conducts electricity. When you say you got nothing, I'm confused. Do you mean you got an open wire?

Try switching ohm scales on the multimeter. A good resistance wire will measure up to 1 K ohm per inch, so a 12" long wire can measure up to 12K ohms and still carry a good spark. Forget the "bright blue spark" advice when jumping to ground - - - -that's at least 50 years out of date- - - - -even a good resistance wire will produce a yellow/orange spark.
Jerry

I just found my inline spark tester and It lite up fine at the end of the plug wire, so it appears I have juice to there. I pulled off the plug connector and no change to the engine . So then I did a dry compression check to eliminate the mechanical possibilities and had 105 lbs there. Then I switched the plug to another cylinder and the miss magically appeared on that cylinder.

So what plug should I use on a 216 with a 12 Volt conversion???

Spark plugs don't care if the truck is 6v or 12v. The coil is sending 20,000+ volts to the dizzy and then to each plug.

I assume this is for the '46?

Autolite 3136 or AC Delco M8

A bad spark plug is not at all uncommon these days. I’m guessing yours doesn’t look fouled.

Isn't that crazy how you can't rely on ANY new parts to function as new? It used to be that if you put in a new part you could cross it off the list as a possible suspect. Nowadays you have to test all the crap you didn't replace along with all the stuff you just installed!

Check the gap on the "bad" plug. If it's correct, I guess it's bad then. Buy another plug that is the same number as the good ones....or a crossover equivalent.

Regarding continuity tests: Most meters have a section on the dial for "continuity" and they buzz. If not, then you set it to ohms. As JonG is saying: If you see any value on the display, you have continuity. 0 is a reading, or 0.0 is a reading. There is continuity. The instructions will state how your meter displays continuity.

As said, the range is important. Set it to the lowest range. Probably 200. )))) is the symbol for continuity buzz test.

If you see OL "open loop", no continuity. If you see ---- no continuity.

All this is provided you have the leads plugged into the correct meter jacks. Ignition key off may be necessary. You never check continuity with power on a circuit.

Very smart using the timing light. I learned that trick long ago when working on outboard motors.

So let me answer all this. This engine is on my 52 one ton. The 46 is in pieces and I have a good 235 for it sitting in my garage. The plug was black but not fouled for some reason and properly gapped. The meter did say OL. I started on the 200 scale but dropped it down to the 20 scale. I have a Klein multi meter, it has a position for Ohms and only requires changing the leads when reading Amps. This about the second time I have used it and really like it. My Snap on test light finally bit the dust after about 50 some years and I got a new one one that reads volts in addition to lighting up. I don't know how valuable an option that is but it looks cool and can probably help find a voltage drop between two places. Otto, I have Champion UJ 12Y plugs now but will look for the Autolite or Delco ones.

Thanks All,

The '52 will use different plugs than the '46, I believe.

Anything is better than Champion. They're about the worst plugs you can buy.

Motorcraft SP476 or Autolite 303

I have AC43 in my truck but I generally prefer Motorcraft.

Went thru the same issue with the multimeter on spark plug wires last week, tone/continuity did not register, switched to resistance and got readings, tested a known good/used wire and used that as my reference, I always say you need to test the test eqpt (multimeter) before taking a reading so you know the settings are correct and what to look for…..

Are you running the plugs with the tiny 10MM thread, or the later 14MM ones? It doesn't take much of a carbon deposit on the small plugs to short them out so the voltage leaks away down the tip of the insulator instead of jumping the gap and lighting off the fuel in the cylinder.
Jerry

Mike what model Klein do you have ? MM300, MM400, MM700........

"If it works, it's a Fluke!"

OK, HRL, I don't have the fine threads, and am going to find some AC R45S plugs, to replace the champions. Based on a posts of yours and Wrenchbender from years ago. I hope they are still being made. Bartomos, my meter is a Klein MM300. I got it to have a ammeter option. I was checking for a draw on a dodge truck. Then I closed the door tight and solved the problem. I like the meter, does all I need.

Personally I wouldn't trade my old Simpson 260 for all of the digital meters in town. Of course I was in tech school from 66 thru 68, long before digital meters. But I find analog meters much more straight forward and logical. I do use both though.

Mike, the AC45 plug has been discontinued for a long time. It was the factory plug on my '50 Stovebolt, '66 Toronado, and '56 Cadillac.

The in-service replacement is the AC43. I use that plug in all three vehicles and have no problems whatsoever.

There are a lot of AC45s for sale on ebay at around $10 each

https://www.ebay.com/sch/i.html?_fr...13&_nkw=ac45+spark+plug&_sacat=0

The AC 45 is a "hot" plug that was intended for short trips at low speeds like in town or delivery vehicles that saw limited highway driving. 43 and 44 plugs dissipate heat from the tip to the thread area a little faster, which makes the tip less likely to erode from overheating on a long haul. It's a compromise between running a plug tip hot enough to keep deposits burned off, and cool enough not to erode the electrodes or blister the porcelain insulator.
Jerry

I found some R45S plugs at a FLAPS I only use once in a while. $3.10 a piece. I should go there more often good place. I will get them in as soon as I can and see what happens. Thanks everyone

The extended tip plugs (S type) work great in o-head valve engines. I used them for 50 years. So have practically all original equipment manufactures. In my opinion you have made the right choice.

George

Thanks George!

So I replaced my plugs and it was like a miracle happened. The engine ran great until it flooded out. Now I am back to the carb. This carter YF story will belong in the engine section.

I too still have my Simpson 260 from the 60's. Wish it wasn't so big though.