1976 Jeep CJ5 voltage drop at coil

Tiny
ROCKSCARBRO
  • MEMBER
  • 1976 JEEP CJ5
Electrical problem
1976 Jeep CJ5 6 cyl Four Wheel Drive Manual 100K+ miles

I just did an engine swap. Removed '76 258 cid and replaced with '78 258 cid. Now, voltage drops from 12v to 6.8v when the wire is hooked to positive side of coil.
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have the same problem?
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No
Friday, August 27th, 2010 AT 11:09 AM

6 Replies

Tiny
CJ MEDEVAC
  • EXPERT
See my profile and other CJ 5 and CJ 7 answers I have given. The CJ 5 and CJ 7 Forums may provide you with additional info about your Jeep!

YES---You should have a reduced voltage there!

The only time you get FULL BATTERY VOLTAGE to the coil is during "CRANKING"

During cranking...Full 12V + ......will override the RESISTANCE WIRE (reduced voltage) Which begins, basically, at the "ON" position of your Key/ Ignition and travels to your coil. This Resistance Wire feeds your coil a reduced voltage all the time, after you start up.

This TEMPORARY OVERRIDE occurs because "I" terminal on your SOLENOID is "HOT" only while cranking...it dies off when you release the key.....this action gives a better "Jolt of Juice". to the coil..while the Starter is Robbing power

"I" terminal is a direct feed to the coil (full battery voltage).....only momentarily....only till you crank up.

Your Ignition system does not need "FULL JUICE" to run it....On older stuff, Such as My '46 Willys, this prolongs Points' Life.

After Mr. Jeep Starts and you release the key...He reverts back to the reduced voltage.

Your "Built In" resistance wire takes the place of a COMMON/ OLD STYLE Ceramic Resistor.

NOW, are we having issues or troubles because of this, or are you just concerned because it "Just did not make sense"?

Give me something Challanging!

I can help you with MOST ANY CJ ISSUE

Seriously, I am a member like you...I try to give answers a 1st grader can understand! I will work with you on a more personal level, and I try not to throw out Super-Technical Mumbo-Jumbo....I also can share pics and explanations of MOSTLY MECHANICAL MODIFICATIONS (I invented or made, to make my Jeeps "user friendly")

Follow POS BATT CABLE, It will end up here, at the SOLENOID, looks vary, function is the same.

If you are a CJ...Your stuff should be hooked up to the same terminals I show below....Pay attention to "S" and Battery Cable....They should be side by side


http://www.2carpros.com/forum/automotive_pictures/411289_A_B_C_D_EXPLANATION_2.jpg



http://www.2carpros.com/forum/automotive_pictures/411289_A_B_C_D_17_LOCATIONS_2.jpg


"FORD TYPE" SOLENOID SYSTEM, YOUR ACCES., MAY VARY

1) POSITIVE CABLE FROM BATTERY

2) OUT TO STARTER MOTOR

3) ON MY JEEP, THIS GOES TO THE ALTERNATOR

4) THIS FEEDS MY FUSEBOX (ALL OF MY ACCESSORIES)

5) "S" WIRE IS FROM KEY, 12V ONLY WHILE YOU ARE "CRANKING"

THIS WIRE ACTIVATES THE SOLENOID'S ELECTROMAGNET, WHICH IN TURN, CONNECTS---A & B INTERNALLY (ONLY THE 2 LARGE GAUGE CABLES CAN HANDLE THE AMPERAGE THE STARTER "PULLS").

WHEN THE SOLENOID IS ACTIVATED, IT THROWS 12V TO STARTER USING THE LARGE GAUGE CABLES (1) POS FROM BATT--THRU SOLENOID INTERNAL CONNECTION--(2) TO THE STARTER, WHILE KEY IS IN "CRANKING" MODE.

THIS IS THE TOTAL REASON FOR A SOLENOID, BECAUSE IT WOULD NOT BE PRACTICAL, TO RUN THE HEAVY CABLES TO AND FROM YOUR KEY SWITCH.

6) "I" WIRE (OPTIONAL), FEEDS COIL "FULL 12V", ONLY WHILE "CRANKING", AFTER YOU RELEASE THE KEY, THE COIL REVERTS BACK TO REDUCED VOLTAGE, SUPPLIED BY YOUR KEY IN THE "RUN" POSITION.

7) "MOUNT" GROUND, UNIT MUST HAVE A GOOD GROUND (BATT. TO ENGINE, ENGINE TO FRAME, FRAME TO BODY [ALL MUST CONNECT, SOMEHOW] )

(3 & 4, ON MY JEEP) ARE FUSABLE LINKS, ALL ARE NOT MARKED, MY #3 IS, #4 IS NOT....ITS SORT OF A "WIRE" FUSE.

IF THEY ARE GOOD, TUGGING ON THEM WILL BE JUST LIKE A WIRE, WHEN THEY ARE "BURNED UP", THEY WILL STRETCH OUT LKE A RUBBER BAND

Please respond...Read my profile...Did I misunderstand your question?

The Medic
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Friday, August 27th, 2010 AT 5:23 PM
Tiny
ROCKSCARBRO
  • MEMBER
Thanks for the info. That's helpful. My main problem is that I'm getting little to no fire from my coil. So, I'm not getting it to start.
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Saturday, August 28th, 2010 AT 8:36 AM
Tiny
CJ MEDEVAC
  • EXPERT
Roger. Several possible reasons, The worst is probably wires tampered with!

Need some info here,

On my '77 I had a Prestolite Ignition system. The Ign. Module would go bad often and disributor had several issues A) The teeny little entrance wires would break B) The diaphrams contained in the circle looking dealees where the vacuum line entered would tear/rip/leak. No advance and vacuum leak was the result.

So I'ze decided to install a '79 Ford Type (what AMC finally used----SO MUCH BETTER SYSTEM!) The Dist. Remanf. At Advance Auto was about $50. Salvage yard provided 2 BLUE Modules and several sets of connectors (Ford Rigs of the '80s are the same, except for there are several different modules---you need the BLUE. Or you can get it new at the parts store).$10 at the yard I frequent.

I drew up a Diagram of what I had to do (15 or so years ago). Had it in my hand yesterday. It's tucked in one of my manuals.

THAT WAS ONE OF MY BEST MOVES TO CHANGE-OVER!

OTHER THAN DOING THAT--CAUSE YOU HAVE NOT TOLD ME WHAT SYSTEM YOU HAVE----OR MAYBE YOU TRIED TO CHANGE-OVER between the 2 engines. And "Botched It"

Not making fun of you.I've had those experiences too!

I can maybe get you a copy of my "Nelsomatic Diagram" If you need it.

It could be that your Ignition Module is bad (either system). Test old one at Autozone or Advance Auto for FREE, Test 5-7 times in a row and quickly, this heat up its guts! If it fails once (That is after the Tech figures out the correct plugs and settings) REPLACE ITTEST THE NEW ONE THE SAME WAY BEFORE YOU LEAVE! TRUST ME. No matter what "THEY" say!

It might be your pick-up in the DIST. ----I've seen that once (and it may have been tampered with). Usually its the Dist. Entrance wires. Worse on the Prestolite.

Mr. Coil could be bad----I can help you tru various tests. More info from you, and your abilities, and Electrical Diagnostic Equiptment?

Gotta sorta have a direction to go. What you have done. What your buddies have torn up!

Do you have a manual. Which one?

If I have lost you.I will stop and explain more.I am here to help you. This is my Hobby. And recently I have achieved a small compensation at this Site----I did not ask for it, or sign up as a Certified Mechanic (which I am not) and make the "Bigger Bucks"

They have reviewed my "Answering" and decided to Up me to "HELPER STATUS". What a Deal. All I wanted to do was help people--Mainly Jeep People (CJs are my cup of tea)

Really the only thing I crave is a Response, or many.I LIKE TALKING CJ!

We can continue right here with as many problems as you can muster. If you want ME to continue to help.

I am "Alerted" any time one of the posts I have answered has "Activity"

So bring me up to date on the situation w/ some detail.I have little else to do on my end!

I usually try to write you a Novel. Personal to your situation. It's not fair, you writing 2 lines. With little for me to go on!

Hope I make another Jeep Friend

The Medic

PS. Remember the RESISTANCE WIRE. YOU MUST RUN A COIL THAT SAYS, "FOR USE WITH AN EXTERNAL RESISTOR" (cause you have an external resistor [wire]) The other type coil will have a resistor INSIDE----NOT GOOD.2 resistors in a row, cuts down on voltage even more!
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Saturday, August 28th, 2010 AT 9:49 AM
Tiny
ROCKSCARBRO
  • MEMBER
Hey Medevac, Here's the deal. The jeep was starting to run rougher and rougher. I tuned it up a bit, sealed up some oil leaks, then took it for a drive. It didn't run much better and the pcv valve was clogged, so the pressure from the worn out rings caused the valve pan cover gasket to blow out. I did a compression check to find 85 lbs of compression on all 6 cylinders. I decided to swap the engine out for anther one I took from my previous cj-5 (1978). This one had a different style ignition module, distributer and solenoid.
WhenI finished the installation with all of the electrical components that I had been using, it would not fire. I checked it at the coil and found a weak spark on rare occasions while cranking. I decided to try all the of the electrical components that came with that engine originaly (coil, distributor, ignition module, solenoid and engine wiring harness). Still nothing. I tried 3 different used coils (all for use with external resistor), still nothing. What I don't understand is how I lost fire by changing the engine and not anything else. I suppose all of my coils could be weak. I thought I'd go get new plugs, wires and coil when I get back in town.
I'm really a chevy man and have the new rebuilt 350 in the garage waiting to go in as soon as I get the bell housing to bolt it to my t-18b, but I just lost the contract on my job. This swap was the affordable option. Thanks for all the helpful info thus far.
-Rock-
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Saturday, August 28th, 2010 AT 8:13 PM
Tiny
CJ MEDEVAC
  • EXPERT
OK Buddy---you can no longer be a "Bowtie Guy" You must convert.I can Help!

I am having "EPSON" printer issues----I am still trying to scan my Diagram. To send you

Verify you had a Prestolite System and Now you will have a Motorcraft Type.

I feel sure my diagram will help you!

Seems that when this Darn Printer is out of ink. None of its Unrelated Functions. Function without it. Or I ain't figured it out yet.

If I cannot get it thru tonight.I will get ink and do it tomorrow. BEAR WITH ME!

I saw you were in the Site while ago, been waiting for your response

The Medic
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Saturday, August 28th, 2010 AT 8:33 PM
Tiny
CJ MEDEVAC
  • EXPERT
OK here it is---I thought I had Prestolite on here too.

This should be the finished product

I took it to paint and tried to connect the colors (where they paused at text) I just went under the text w/ color at "Paint"

The colors should be correct '76-'79

I can explain further where these wires continue to

Most of the rest is Connectors

Waiting on you

The Medic

I just preveiwed this, it is Unreadable

I will now send you a "PM" private message....NOW!...Gimme your Email there... I will send it direct and it will probably readable


http://www.2carpros.com/forum/automotive_pictures/411289_DISTIGN_MODULE_colored_in_1.jpg

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Saturday, August 28th, 2010 AT 9:07 PM

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