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Kahuner 03-20-2012 07:31 PM

Need Electrical Help- Turn On Headlights & Tach Quits
Looking for someone to walk me thru the troubleshooting steps to resolve my electrical issues. Here's what I'm working with:

1989 YJ 4.2L 5 Spd w/ a reman engine that I installed 2 weeks ago
Nutter Bypass
Team Rush Ignition Upgrade & M/C 2150 carb

The ignition upgrade may be part of the solution because I may have done something wrong trying to implement the ignition upgrade.

I don't know where to start (in my explanation) other than to say when I turn on the H/L with the engine idling; the tach quits and the engine starts to run rough........ obviously a short between the H/L wiring & the ignition system. Most recently I blew the starter relay AND a fused link that has 2 fused green wires to 1 eye terminal at the stud on the relay. Each of the green fused wires go to separate red wires in the wiring loom.

I'v replaced the relay and the burned up fuseable link and the engine still idles rough and the tach quits if I turn on the lights.

Can anybody help me troubleshoot where the short may be?

Any help would really be appreciated!!

Master4th 03-20-2012 09:40 PM

Sounds like you have a short.

In these vehicles for the most part the lights are seperate from anything else as far as power goes. This is becuase lights have power available all the time. Where as your ignition system, accessories [radio ect.] only have power when in acc/run key position.

I would start with back tracking the wiring you have recently done.

Check all your ground points, the lights have 2, 1 on the passenger, 1 on the driver front.

The reason a short, or power draw down can make it run rough would be becuase the coil and therefore the distributor are not getting enough power to make the proper spark.

Just to recap
1. Retrace any wiring you have recently worked with.
2. Check all grounds, make sure they are clean and secure.
3. Use a multimeter and watch the voltage, and amps while you turn the headlights on.

This is where I would start.

Kahuner 03-21-2012 01:40 PM

Thanks for the reply Master4th!

New info:

1. Engine runs rough at idle w/ H/L on. Better if H/L are off. Hasn't changed.

2. If the dash light rheostat is turn down to off or minimum; or if the rheostat is disconnected; engine will NOT start. If the rheostat is set at 3/4 bright, engine fires right up. Obviously the starting system is using the H/L circuit for a ground?

Any other or new ideas?

Kahuner 03-21-2012 02:52 PM

Fixed the issue regarding the rheostat effecting starting. That was caused by a bad ground on the starter relay. It's the black wire w/ the white tracer. Disconnected the black/wh tracer and made a new wire to ground the "G" terminal on the relay to abody ground.

Black/white tracer is still disconnected from the starter relay (connects to a spade terminal). What is that wire for?

The only remaining problem is the tach quits when I turn on the lights. Both grounds are good connecting to the radiator grille.

Dutch 95 03-21-2012 10:40 PM

I must have looked at your wiring diagram for two hours last night, and I'm truly at a loss here. The one thing that I did notice is that one of the green fusible links in the wiring diagram supplies the lighting, and the other supplies the start relay, ignition module and tach. It seems like somehow there is a wire switched. The rheostat seems to be controlling the ignition circuit, so as you turn the rheostat you off cut power to the ignition module, and when you actually turn the lights on, it isn't powering the correct relay. Without being right there, this is all I can provide for help. I'll keep checking in and hopefully this helps.

Dutch 95 03-21-2012 10:54 PM

Ummm...wait you said black w/ white tracer on the starter relay? According to the diagram, the black w/ white tracer should supply the illumination to the tach and other gauges. The starter relay should only have a black. Maybe that would be a good place to start.

Is there another relay in close proximity that the wires may have been switched? I don't have an 89, so I don't know the layout of the relays.

Kahuner 03-22-2012 06:02 PM

Found the problem!!!

As I mentioned earlier, I fixed the rheostat & starting issue by running a new ground wire from the "G" term on the relay to a chassis ground. The only remaining problem was that the tach would quit when I turned on the lights. Fixed the by connecting the Blk/Wh tracer to a new chassis ground as well.

Lessons learned: when I bypassed the ECM during the Ignition upgrade install; I must've disturbed a ground for the ignition along the way.

Thanks Master4th...... just like you said: "check the grounds". Truer words were never spoken!!

Woo-Hoo; I feel like I just got a pardon by the Governor!!!:dance:

Now where's my sippy-cup and the vodka bottle?

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