Ignition wire question

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CherokeeJim
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Joined: Sun Sep 16, 2012 5:51 pm
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Ignition wire question

Post by CherokeeJim »

:fsj:

Installed a new Howell efi system on my 77 Cherokee with a Z&M engine harness which replaced my factory harness.
The blue wire going to my starter solenoid on “I” post, with key on and a circuit tester, my blue solenoid wire makes my circuit tester flash instead of showing a constant light.
All my exterior lights work. I have no lights on in my dash other than my clock, my interior lights do not work unless I rotate my headlight switch counter clockwise to turn on the interior lights.
My CD player works but no sound to my speakers and no power going to my amps.
My concern is not the interior stuff, I can tend to that stuff later.
My main concern is my ignition system.
Why does my blue wire make my circuit tester flash instead of a constant light?
I have no power to my fuel pump, no power going to my injector harness using a noid light.
I’ve worked on tons of FSJs and owned several but I have never encountered this problem before.

Mind you, my FSJ has been sitting stored for two years.

Thank you in advance for any and all help.

V/R,

Jim
'77 Cherokee 6" lift/6.6L/TH475/BW1339/D44s/4.56s/35x12.50x15s/ Detroit rear :fsj:
'82 J10 6.0L/6L80E/Atlas 3.8/SOA with 2" front springs/ 63" springs inboarded/D60F/Spartan Locker/14Bolt/Detroit 4.56s/42s
'71 J4000 on 81 J10 frame/6bt/4500/203-205/D80F D80R/ARB/Spool/5.13s/42s
'79 Cherokee 4dr 6.6L/TH400/BW1339/D44s/3.54s :fsj:
'08 Tundra 5.7L 3" lift/33s
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Stuka
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Re: Ignition wire question

Post by Stuka »

What key positions is it flashing in?
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

Topic author
CherokeeJim
Posts: 205
Joined: Sun Sep 16, 2012 5:51 pm
Location: Texas
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Re: Ignition wire question

Post by CherokeeJim »

:fsj:

I know I stated “I” post, let me make a correction. I really meant “S” post.

With the blue wire that goes to the “S” post, using a circuit tester, and that blue wire NOT connected to the starter solenoid, if I touch my circuit tester to that terminal on the end of that blue wire, my circuit tester light flashes instead of staying on as constant.

This happen with the key on the ON position, and not cranking the engine.
If I turn the key far enough to crank the engine, the engine will crank.
'77 Cherokee 6" lift/6.6L/TH475/BW1339/D44s/4.56s/35x12.50x15s/ Detroit rear :fsj:
'82 J10 6.0L/6L80E/Atlas 3.8/SOA with 2" front springs/ 63" springs inboarded/D60F/Spartan Locker/14Bolt/Detroit 4.56s/42s
'71 J4000 on 81 J10 frame/6bt/4500/203-205/D80F D80R/ARB/Spool/5.13s/42s
'79 Cherokee 4dr 6.6L/TH400/BW1339/D44s/3.54s :fsj:
'08 Tundra 5.7L 3" lift/33s
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Stuka
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Re: Ignition wire question

Post by Stuka »

Ok, so the 'S' position should only get full voltage when the key is in the 'Start' position. If its in the 'Run' position, you should not get constant voltage. This terminal will send a straight 12V to the coil, bypassing the ballast resistor that normally drops the coils voltage down to around 7-8V.

If you are touching the end of the blue wire, without being connected to the 'S' terminal, it sounds like you are probably picking up the coil signal from the ignition box or something. I have never hooked up a multimeter to that wire to see what it reads in that scenario.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

Topic author
CherokeeJim
Posts: 205
Joined: Sun Sep 16, 2012 5:51 pm
Location: Texas
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Re: Ignition wire question

Post by CherokeeJim »

Ok, I have an HEI dizzy, I used the coil signal wire to my HEI when I restored my Cherokee. Ran fine for many years with a TA670. Stored the Jeep for 2 years, pulled it out of storage, threw on an EFI. I did not change any wires to my HEI. Not sure what happened while in storage. No mice or anything got in the Jeep and chewed anything up. Secure storage. Its like my Jeep wire harness developed a mind of its own. I'm using a Z&M Harness from front to back as well as engine harness. All my exterior lights work great, my interior lights only work if I rotate my headlight switch counter clockwise to turn on the interior lights. My CD player comes on but no music through my speakers and no power to my amps. The engine does crank.
I'm not concerned with the interior stuff at the moment. I can address those issues easily enough. I'm wondering if I have a bad ignition switch (my ignition key switch is located in the dash now as I have a Flaming River Steering Column without key in the column.
'77 Cherokee 6" lift/6.6L/TH475/BW1339/D44s/4.56s/35x12.50x15s/ Detroit rear :fsj:
'82 J10 6.0L/6L80E/Atlas 3.8/SOA with 2" front springs/ 63" springs inboarded/D60F/Spartan Locker/14Bolt/Detroit 4.56s/42s
'71 J4000 on 81 J10 frame/6bt/4500/203-205/D80F D80R/ARB/Spool/5.13s/42s
'79 Cherokee 4dr 6.6L/TH400/BW1339/D44s/3.54s :fsj:
'08 Tundra 5.7L 3" lift/33s
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tgreese
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Re: Ignition wire question

Post by tgreese »

If you look at a wiring diagram from a later year, the light blue wire should connect to the Duraspark ignition module. It also bypasses the resistance wire for the ignition and sends full voltage to the coil for starting. Both of these functions are irrelevant for either the original Prestolite ignition of a '77 or when converted to the HEI distributor.

On a '77 harness, there is a single blue wire to the starter solenoid that energizes the solenoid. Nothing to do with ignition.

I would use a multimeter and trace it back to its origin, and see what it's now connected to.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

Topic author
CherokeeJim
Posts: 205
Joined: Sun Sep 16, 2012 5:51 pm
Location: Texas
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Re: Ignition wire question

Post by CherokeeJim »

Using a multimeter, what amount of voltage should I be looking for? Also, why would that wire cause my circuit tester to flash? Shouldn't I have a constant signal with the key on/run position or not?
'77 Cherokee 6" lift/6.6L/TH475/BW1339/D44s/4.56s/35x12.50x15s/ Detroit rear :fsj:
'82 J10 6.0L/6L80E/Atlas 3.8/SOA with 2" front springs/ 63" springs inboarded/D60F/Spartan Locker/14Bolt/Detroit 4.56s/42s
'71 J4000 on 81 J10 frame/6bt/4500/203-205/D80F D80R/ARB/Spool/5.13s/42s
'79 Cherokee 4dr 6.6L/TH400/BW1339/D44s/3.54s :fsj:
'08 Tundra 5.7L 3" lift/33s

Topic author
CherokeeJim
Posts: 205
Joined: Sun Sep 16, 2012 5:51 pm
Location: Texas
Contact:

Re: Ignition wire question

Post by CherokeeJim »

:fsj:

I found my issue.
I have a bad ignition switch.

Thanks for all the help fellas.
'77 Cherokee 6" lift/6.6L/TH475/BW1339/D44s/4.56s/35x12.50x15s/ Detroit rear :fsj:
'82 J10 6.0L/6L80E/Atlas 3.8/SOA with 2" front springs/ 63" springs inboarded/D60F/Spartan Locker/14Bolt/Detroit 4.56s/42s
'71 J4000 on 81 J10 frame/6bt/4500/203-205/D80F D80R/ARB/Spool/5.13s/42s
'79 Cherokee 4dr 6.6L/TH400/BW1339/D44s/3.54s :fsj:
'08 Tundra 5.7L 3" lift/33s
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