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Old 02-24-2010, 06:25 PM
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Multiple Engine Ground Question

I have a '91 Chevy truck that I am in the middle of changing the engine on. There is a thick ground from the battery to the block, and another, smaller copper wire that goes from the back of the passengers head to the firewall, then to the frame. Alldata lists the small ground as an ECM ground for this truck. My friend is also changing his engine on an '81 truck (without an ECM) and he has the same ground setup. I understand why the ground may exist for the ECM, but I don't understand why an older truck that never had a computer would have the same thin, flat wire.

Any ideas?

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Old 02-24-2010, 06:41 PM
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theres no such thing as too many grounds ( cosmetically there can be ).. possible on his truck it's a starter ground
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Old 02-24-2010, 06:49 PM
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Not likely. It's thin and attached to the head. The starter probably grounds better from the 4-gauge attached to the block. (I would think)
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Old 02-24-2010, 07:52 PM
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Quote:
Originally Posted by Pre-Tuner
Not likely. It's thin and attached to the head. The starter probably grounds better from the 4-gauge attached to the block. (I would think)
tail lights , gas gage and such , never enough grounds like matt said
motor mounts and exhaust not a good ground .
used the flat braided on both sides of motor to body .
does yours and the 81 have small ground wire from body to battery hook up ?
most do , known to corrode up and fail .
never enough grounds .
yours the wiring harness is grounded to thermostat or intake bolt for the ecm ?
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Old 02-24-2010, 08:41 PM
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As Matt said, never enough grounds. You could throw soil in the trunk and it still wouldn't be enough ground.

Seriously, if anyone thinks they have a good enough ground from the factory, hook your ground clamp on the tail pipe and try to get a quality weld on the front fenders.
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Old 02-24-2010, 10:02 PM
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I understand grounds are good. I already added one from my alternator to the chassis and that helped with the charging. It just seems odd that there would be a "huge" 4-gauge ground a foot and a half from a little tiny ground. I guess my question is what's the little ground doing that the big ground isn't on a non-computer controlled vehicle? The only thing using electricity is the ignition (dist., plugs) and the choke. The temp sensor is resistive, and the alternator is on the other corner of the engine.
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Old 02-24-2010, 10:27 PM
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grounds

Ford used a grond clip on the top of the firewall that scratched the hood for better radio operation, less static.
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Old 02-25-2010, 04:13 AM
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thats for the ground plane of the radio , pontiac did that also on the firebirds as the windshield had the attena in it . with a common gorund system you want many redudents as possible , my 96 chevy only has one ground for the starting circuit and its wire that runs to the front of the block all the way down near the timing sensor ( the block is wired to the battery and there where flats running to the frame and cab , when the wire broke , the truck was dead in the water no start or iginition circuit , I have several heavy grounds on the truck from the battery to the block to the frame rail and one to the bed and 2 two the cab and have moved the ecm ground wire . , my firebird when it had rubber mounts on the subframe it would do goofy things like diming lights, the radio would change volume , dash lights would glow , after the battery went into the trunk and I hard wired the subframe to the body and to the engine block with cable then things changed , and one of the original wires you could see where it was making contact with the body and arcing .
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Old 02-25-2010, 10:11 AM
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Try doing a 'glass' car sometime. You will discover a new meaning for grounds. I have 4 major ground terminal blocks grounded to the frame from both ends , battery to frame, frame to motor, block to aluminum heads, every electrical device has at least one ground wire that needs to be connected. I used black for all grounds and various sized wires. So far no problems due to grounds. The only problems is some cross talk from parallel wires. This will be taken care of by twisting the wires upon reassembly.

Every time something is added the first thing is to plan on where the ground wire goes. Then sender and or power wires. Terminal blocks simplify most of the grounds and provide clean connections.
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Old 05-19-2010, 03:47 PM
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I know this thread is older but i have some questions.

I have my battery in the hatch area of my 73 nova. The batterys ground is about 12" long and bolted to the body. My engine has one of those big braided straps from the block to the chassis. My car has one of the electric cut off switches at the rear of the vehicle.

Lately i've been having issues with my radio sounding like its cutting out and lights will dim/flicker, i've been checking my grounds, replaced the alternator....nothing has helped.

When i was changing out my Alt i turned the electric cut off switch to "OFF" while i was disconnecting the Alt I some how was able to arc a huge spark off the alternator, i could probably repeat this but i obviously didnt want to so I became very cautious/careful.

With my battery basically 'disconnected' how could i get a spark like that at the alternator?!?! Is this the cause of my problem? Is something building up power and waiting to discharge on a ground? Do i need MORE grounds? Maybe ground my alternator? Throw a ground strap from the trunk area of my hatch to the chassis?

Any thoughts/ideas are very appreciated!
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Old 05-19-2010, 05:23 PM
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It depends on how your battery disconnect switch is connected. If it's right at the battery and breaks the positive or negative lead before any branches off either it will kill everything. On GM cars there is a hot at all times lead from either the battery + or a battery + terminal block on the firewall to the alternator.

Vince
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Old 05-19-2010, 05:34 PM
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Quote:
Originally Posted by Ignitrous
Lately i've been having issues with my radio sounding like its cutting out and lights will dim/flicker, i've been checking my grounds, replaced the alternator....nothing has helped.

When i was changing out my Alt i turned the electric cut off switch to "OFF" while i was disconnecting the Alt I some how was able to arc a huge spark off the alternator
For there to have been a large spark at the alternator, there would have had to have been a short to ground and/or a loose connection. Possibly an internally damaged alternator. Depending on how you are wired, the hot from the rear-mounted battery could go directly to the starter, then a wire up from the starter to the alternator's "BATT" lug.

I'd recommend for you to install a trunk- (hatch) mounted remote Ford-type starter solenoid- aka relay- to power the starter w/a 1-0 gage wire that will be dead when the key is anywhere except "START".

If you have no NHRA need for that kill switch, you could remove it.
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Old 05-20-2010, 12:04 PM
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I added a few grounds last night and it didnt help.

After the car heats up to normal operating temperature (180-195*) my radio will begin to cut out and i can watch as the display on my CD ignition box begins to flicker which causes the car to bog/cut out/lose power.

When the vehicle has sat over night or for a few hours since last being started it will take a little while before it begins to do this again. What heat (im assuming its heat) would cause this??? Im almost ready to just sell the car and end this headache.
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Old 05-20-2010, 12:23 PM
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Check to see if your type of ignition box is tied directly into your coil pack. I have seen a bad coil pack cause an electronic ignition box to act real stupid.
You most likely have a one wire alternator and it is probably fed straight from your battery - make sure all hots are connected to your cut off switch.
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Old 05-20-2010, 12:31 PM
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Sounds like this to me, first the spark at the alternator, tells me that the cut off switch is not wired correctly, whether the switch opens the circuit on the neg, or the positive side of the battery circuit, it should not have done that. Best practice is to have the battery cut off switch open the ground, negative side so as to not spark, arc the contacts of the cut off switch .

Second the CD box blipping, this can be caused because of the location at which the main power that feeds that box, large red wire is tied into the main circuit. That large red wire should be wired directly to the battery positive terminal . Who is the ignition manufacture, Crane by chance ?

Alternator is grounded via the hardware that mounts it .

Last edited by pepi; 05-20-2010 at 12:39 PM.
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