blue coil, ballast resistor, and crane 700

[2002iii]

When the car dies on you try touching the coil and ignition box with one finger. The one that is to hot to touch is probably the culprit.

[Bad Dad]

Thanks again for all the great information. 
 

Both the Crane and the coil seemed warm, but the coil was scolding. I have an oil filled 3 ohm Pertronix coil arriving today and will report back once installed. 
 

It seems to me the resistor was bypassed to the coil, but not to the Crane (red wire)? With the new coil I will run green + red on positive and yellow on negative. (The two black cables are tach and electronic choke). 
 

I want to get rid of the Crane eventually as I don’t know its age, and I want to make the car reliable. The car is new to me, and PO claims to never had these issues so I’m puzzled. 
 

I will go with a Hot Spark module in the existing distributor if it seems viable, or a complete 123 unit. 

[John76]

6 hours ago, Bad Dad said:

It seems to me the resistor was bypassed to the coil, but not to the Crane (red wire)?

I looked closely at your pictures and the Crane wiring diagram. My eyes may be playing tricks on my old brain...

The way you have it, the signal from the Crane (red wire) is going through the resistor and the +12V from the "run position" on the ignition switch is indeed bypassing the resistor. The black wire should be plugged into the black/white wire on the starter.

I made a sketch comparing what you show and what the wiring should be. Perhaps the problem you are experiencing is due to the red wire being "resisted" and the coil receiving a full +12v (no resistance) when in the normal run mode.

What is the recommended coil resistance for use with the Crane 700?  Should be stated somewhere on the unit?  

 

John

 

  

 

[Bad Dad]

Indeed, this looks right to me. The only thing I wonder about is whether that resistor is needed on the green? Is the coil receiving too much current while running without it? As far as I know I have no black wire going to the starter. I have one on the + going to the electric choke. On the negative a black wire is feeding the tach (all I know since disconnecting it stops the tach from working)

 

From the Ignition Coil Guide:

Quote

Essentially, the "external resistor" coil is just a coil that is designed to work properly when supplied with about 9 volts. It is then used with the external ballast resistor so it can safely operate continuously when supplied with the usual 13-14V available when the engine is running. Since a coil's current draw is directly related to the amount of spark energy it might deliver, more current is naturally better except that a coil's current has to be limited to an amount that would not make it overheat in continuous use and/or burn out the points prematurely.

 

I received a new, oil filled, Pertronix 3 ohm coil today and took for a test ride. It is connected according to your bottom drawing, sans resistor. The car ran great, and didn't stall once. I do have to say, that when returning home, the new coil was very hot to the touch, but perhaps this is normal? I will take it for a longer drive tomorrow, but so far it seems very promising.

 

The crane calls for 3 ohm as far as I know. However, since I have no history on the unit, and these are getting rather old, it will be phased out of my system with the next service.

Edited August 13 by Bad Dad
Added quote

[Bad Dad]

This has made thinking, perhaps I should look to the voltage regulator?

 

edit: a drive this evening and symptoms persists. Left me stranded. New coil did not solve the issue. I will try John76’s wiring with the resistor on the green. I am also looking at the Optical Trigger, inside distributor. The car runs great until it stalls, so I assume the optical trigger works as it is supposed to. But could it be a culprit in making the coil work too hard?

Edited August 13 by Bad Dad

[Stevenc22]

14 hours ago, John76 said:

I looked closely at your pictures and the Crane wiring diagram. My eyes may be playing tricks on my old brain...

The way you have it, the signal from the Crane (red wire) is going through the resistor and the +12V from the "run position" on the ignition switch is indeed bypassing the resistor. The black wire should be plugged into the black/white wire on the starter.

I made a sketch comparing what you show and what the wiring should be. Perhaps the problem you are experiencing is due to the red wire being "resisted" and the coil receiving a full +12v (no resistance) when in the normal run mode.

What is the recommended coil resistance for use with the Crane 700?  Should be stated somewhere on the unit?  

 

John

 

  

 

 

John, you always have the best diagrams.

 

The original wiring might be correct. According the the diagram posted earlier, the XR700 requires a ballast resistor, but the blue coil does NOT require a ballast resistor. So the way it is currently wired kind of achieves that.

[Stevenc22]

12 hours ago, Bad Dad said:

This has made thinking, perhaps I should look to the voltage regulator?

 

edit: a drive this evening and symptoms persists. Left me stranded. New coil did not solve the issue. I will try John76’s wiring with the resistor on the green. I am also looking at the Optical Trigger, inside distributor. The car runs great until it stalls, so I assume the optical trigger works as it is supposed to. But could it be a culprit in making the coil work too hard?

 

It may be the crane box which is dying. Your next move is likely to install a Hot spark and bypass the crane all together. Then you have eliminated the crane and coil. 

[2002iii]

You can buy a newer version of the crane 700 box, it's sold by FAST as an xr700. It's basically the same thing but better, FAST bought the design from Crane.

[Bad Dad]

Indeed, thanks everyone. I have a Hot Spark on order. Seems like a nice and simple solution.

[John76]

4 hours ago, Stevenc22 said:

So the way it is currently wired kind of achieves that.

Thanks Steven.

I just don't understand why the Blue coil would get so hot and why the red wire to the XR needs a resistor.

@Bad Dad has the black wire from the coil + connected to the electric choke, so you want the full +12 volts (not through a resistor). No need for a Black/white wire to bypass the resistor during starting.

Is this a square light car?? Could be the Blue coil is getting < +12v through a "hidden" resistor wire?

[Bad Dad]

Yes, '74 square.

 

I did the mistake of trying three solutions this morning, so not sure which might have been the correct one. I connected the resistor on the green, pre coil, as per your initial drawing @John76 I replaced the voltage regulator (external type) and I sprayed contact cleaner on the optics inside the distributor to see if I could clean the led's.

 

I have yet to be sure of anything, but I drove to work on a 40 min commute in city traffic mid 80s outdoor temp, and the engine did not stall once. I did observe a constant 13v on my digital voltmeter. Perhaps the regulator was a culprit? I want to try the same on my drive home, but disconnecting the resistor.

 

Either way, I want to try and install the Hot Spark module to have something fresh. The Crane seems old, and one box less in the bay can't hurt imho.

[Bad Dad]

Yes, '74 square.

 

I did the mistake of trying three solutions this morning, so not sure which might have been the correct one. I connected the resistor on the green, pre coil, as per your initial drawing @John76 I replaced the voltage regulator (external type) and I sprayed contact cleaner on the optics inside the distributor to see if I could clean the led's.

 

I have yet to be sure of anything, but I drove to work on a 40 min commute in city traffic mid 80s outdoor temp, and the engine did not stall once. I did observe a constant 13v on my digital voltmeter. Perhaps the regulator was a culprit? I want to try the same on my drive home, but disconnecting the resistor.

 

Either way, I want to try and install the Hot Spark module to have something fresh. The Crane seems old, and one box less in the bay can't hurt imho.

[Bad Dad]

Yes, '74 square.

 

I did the mistake of trying three solutions this morning, so not sure which might have been the correct one. I connected the resistor on the green, pre coil, as per your initial drawing @John76 I replaced the voltage regulator (external type) and I sprayed contact cleaner on the optics inside the distributor to see if I could clean the led's.

 

I have yet to be sure of anything, but I drove to work on a 40 min commute in city traffic mid 80s outdoor temp, and the engine did not stall once. I did observe a constant 13v on my digital voltmeter. Perhaps the regulator was a culprit? I want to try the same on my drive home, but disconnecting the resistor.

 

Either way, I want to try and install the Hot Spark module to have something fresh. The Crane seems old, and one box less in the bay can't hurt imho.

[HBChris]

Your 74 has a resistor wire and a bypassed ballast both of which are incompatible with a blue coil.  If all were connected you would have 1.1 plus 1.1 plus 3.0 ohms of resistance, not good.  Without the ballast you still had 4.1 ohms, again not good.

[Bad Dad]

Thanks @HBChris

I traced the green wire to below the fuse box last night, and it was one solid wire with no disruption for hidden resistor that I could see.