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EZ Wiring Harness Issue

5K views 25 replies 5 participants last post by  John Strenk 
#1 ·
I started installing a manufacted harness. I have the tail, front and engine compartment completed. My problem is the engine cranks and wants to start but doesnt quite catch. It was suggested I check voltage at the pos side of coil. When the key is on, I have full power (12.45) but while cranking, the power drops (down to around 9 and perhaps lower but I stop after a couple seconds). Is this what is supposed to happen? Any suggestions?

I did replace the solenoid with the one in the picture below and have the TFI as shown which was installed with the previous harness. There are two smaller wires one to the S (greenish teal color) and other (red with white trace) to the I terminal that I'm not quite sure their function but believe they tie to the ignition? They were pushed on the old solenoid so I changed the connectors and put them on this one as well. No computer installed/nutter bypass. Thanks in advance for sharing your knowledge. Mike.
 

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#2 ·
It could be a bad Ignition Control Module. You can take it to an auto parts store and have them test it, almost all of them will do this for free.

Usually, if you have proper voltage to the coil (which it sounds like you do) then you are also getting proper voltage to the ICM. This can also be checked. If you have a harness with resistor wires, then your wiring should look like this: Rectangle Parallel Schematic Slope Font


OR if you have a 12V coil and a 12V ICM, then your wiring can be simplified to look like this. However, I would recommend keeping the red wire from the "i" terminal to the + side of the coil: this gives your coil more power when starting. Rectangle Schematic Parallel Font Plan


Credit to JeepHammer for the wiring diagrams. I drew the second one for my own reference on how my jeep is actually wired.

- Brad
 
#3 ·
A couple of other things I just thought of:

1) Is you ICM properly grounded? See the pictures posted above: they show where to add a ground wire.

2) Are the orange and purple wires (from the distributer to ICM) twisted together? They need to be twisted to ensure there is no electromagnetic interference on them, otherwise your spark timing can be sporadic.

3) Unrelated issue: Does the sensing wire on your alternator have a diode in it (or ~16ohms resistance)? If not, your jeep will not stop running after the key is removed. Reference this for more info: http://www.jeepforum.com/forum/f8/alternator-painless-wiring-857838/ Motor vehicle Headgear Automotive tire Sports gear Electrical wiring


I just rewired my engine bay 2 weeks ago and learned a few things the hard way :)

-Brad
 
#4 ·
When the key is on, I have full power (12.45) but while cranking, the power drops (down to around 9 and perhaps lower but I stop after a couple seconds). Is this what is supposed to happen? Any suggestions?
This is opposite of what should happen. There should be full battery voltage at the coil + while cranking. Then it should drop to 6-7 volts with the key in the Run position.

Matt
 
#7 ·
Now I've got the warm and fuzzies. Brad, Matt and now John Strenk! Thanks for taking the time to review my problem fellas. I read and have learned a ton from each of your posts.

I will test the current as John mentions above and get back to y'all.

Matt, I do not have a diode. I will check the ICM ground and verify the orange and purple wires are twisted but I have not done anything with the connections to and from the ICM so I would imagine they are OK.

Again, thanks guys. This is uncharted territory for me and I have a pretty strong anxiety for electrical. I appreciate all your help.
 
#8 ·
Quick update, E-Z Wiring got back to me. Turns out I needed to splice the coil positive wire into the ignition wire (red with white trace) on the I terminal of the solenoid. Started right up! Now to figure out the electric choke, tachometer and internal gauges. I still don't have a diode on the alternator and it seems to shut off fine. Should I add one anyway?
 
#10 ·
I used EZ Wire in an off topic vehicle. Its a good harness. EZ wire will have a dedicated choke wire in the harness. It hooks to the choke connection to heat the spring in the housing. It is hot with the key on only. I have seen some cases where I had to add a ground to the choke housing due to insulated carb spacers and such. Is the tach an aftermarket or factory tach? They hook up very differently. On the gauges, I used a couple of trailer wiring connectors. Hooked the connectors to the gauges and the other side of the connectors on the harness. It allows to to take the take the gauges out easily if they need service. Just arrange the connectors so they cannot be plugged in to the wrong connector.
 
#9 ·
Mike,

Glad you got it figured out. :cheers2:

Regarding the diode, I know Hammer advocates using one, and it certainly can't hurt, but the factory didn't use them and I've never realized a need for one.

I can help you with the tach and choke wiring. Others are more familiar with the gauges. Let us know.

Matt
 
#12 ·
Regarding the diode:
If it ain't broke, don't fix it. Just know that if you have problems in the future, that should be the first place to check. Considering that the jeep already shuts off fine, your wire is likely a resistor wire/has a diode (I can see a bulge in the heat shrink).

Congrats on getting the ignition figured out! It's alot more fun when we succeed. :2thumbsup:

-Brad
 
#13 ·
OK so now I am stuck on the brake light switch. There appears to be a pink wire and a red with gray trace hooked into a connection housing. Both of those go to the brake light switch. I have a brake light power wire and a brake light switch wire. I have tried hooking them up in both configurations with the switch power wire to the red with gray trace and the switch power to the pink and the switch wire to the other. Both configurations without luck. Any suggestions here?
 
#15 ·
Yes and both signals work. As a separate question, when I have the headlights on, the side indicators on the fenders are no longer lit. They are when just the park lights are on and they blink under both occasions. They were not installed previously so I have no idea if that is normal?
 
#19 ·
Do they just splice into the headlight wires then?
Actually they are spliced into the turn signal feed and the parking light feed.

If you have them spliced into your headlights, that may be the problem.

Here is the factory schematic:



Look at lower left hand corner

From Skerr
This is the factory wiring for the front parking lights. The green and white wires go to the lights. The white splices and goes to both parking lights, while the green and green w/tracer go to respective lights. Showing the factory splice for the green w/tracer wire. One of the these green wires goes to the parking light while the other goes to the side-marker light.


This is the factory splice for the white wires. This splits to both front parking lights and the side-marker lights. I removed the tape protecting these splices for picture-taking purposes.
 
#21 ·
I can think of 3 things.

1. A ground issue. If there is a bad ground on the parking lights then the PL find a ground throuh the headlight. As soon as you turn on the headlights, they lose that ground and turn off. Happens all the time. And the Turn signal / parking lights ground through the mounting screws so they won't work with the covers off.

2. Wrong headlight switch.
There was a change half way through 1979 with the headlight switch and the two are not interchangeable. I know Painless addressed this with some clever wiring of the headlight switch but if EZ didn't and wired it up like the original headlight switch, Putting the wrong switch in will cause you problems.

3. There is a mistake in your wiring but you sound like you know what you are doing.

The 4 ways use the same bulbs as the turn signals, work off a different flasher and fuse. it's the same fuse as the brake lights. Do your brake lights work? if yes, It may be the flasher for the 4 ways..

Also, if you are using NEW turnsignal /parking lights, there was a plethora of ones made incorrectly and have the connections reversed, And easy fix, Just push the terminals out of the socket and reverse them.
 
#22 ·
Great suggestions and I have the old headlight switch which I will try today.

How do the grounds tie in to the parking lights? I do not have a separate wire for them and assumed they were just grounded by the screws? Should I run dedicated grounds somehow?

Do you have a simplified diagram of the brake pedal switch? I have a switch in the cab above the pedal with two wire in a housing connector. Picture below.

I also have two wires running out of the brake proportioning valve. What do these tie into?

As always, thanks for the help.
 

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#24 ·
It looks right. Have you tried adding power to each circuit individually with a jumper to verify each circuit works correctly?

The two wire coming off the brake combination valve are for the brake warning light. One wire runs to the light and the other runs to the ignition switch terminal that goes to ground when the switch is in the start position.

They complete the circuit to ground to light up the brake warning light.



There should be a matching plug coming from the firewall connector that these plug into.
 
#25 · (Edited)
I have two wires, one labeled Brake Switch Power and the other labeled Brake Switch. Ive tried connecting these into the brake switch connector housing as pictured above on 2-19, in both configurations without luck. Any suggestions? How does the switch (located above the brake pedal) work?

Also, how/where does the Voltmeter power/feed connect?
 
#26 ·
The voltmeter connects to the ignition switch ACC position.
Either like this:



Or like this:



Notice one has one yellow wire and the other has two yellow wires.

The brake warning light hooks up to the BUSEAT Belt Fuse.



From the fuse box, the brake warning light power goes to the brake warning light in the speedometer.
This light has two wires going into it. The other wire ffrom the light goes to the brake warning light switch on the e-brake and to the combination valve and to the ignition switch. If any of these switches ground out,t the brake warning light will light up.
 
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