micktroup2

I have a 1991 Z28 with the L98 5.7 small block. I am gradually dealing with 22 years worth of problems, but electrical is not my forte. How many grounds should I have, where and what should I check for?

1983Chimaera

I have 4 of the large braided wire grounds on my block, one on the front side of each head from the corner stud of each manifold to the chassis, and one each on the back of each head to the firewall. I also have 10 ECM grounds on my Megsquirt, which is patterned after the factory ECM grounds of a TPI Corvette. Ideally you want as little resistance between your block and chassis as possible. Shoot for 1-2 ohms, max. Ideally you want to be less than 1 ohm if you can. My TPI has .4 ohms from the throttle body on the upper plenum to the chassis. You should also have continuity between the body of the distributor and the block.

Your local auto parts store should have replacement braided wire ground straps in the Help section. Make sure when you attach them to leave slack for engine movement, and scrape away any paint from where the strap attaches to the chassis so as to provide a good ground.

What kind of issues are you having? It's difficult to give any better advice without specifics, but I'll help where I can. I'm a former US Navy Electronics Technician (Submarine), and have worked on radar, communications, gyronavigational, GPS, and Loran systems. As far as automotive, I built the custom harness in my 83 Z28 from a modified 1994 Camaro harness and a stripped 85 Corvette TPI engine harness. It features the 4th gen underhood relay box, a complete emissions delete, ABS delete, SIR circuit delete, custom run lengths to hide wiring and clean up the engine compartment, and integrated maintenance disconnects. It took me 3 months, but I have a harness for my exact needs.

Wiring and electrical can be daunting, but on a car it's a fairly simple system that even a novice can reliably perform most checks on. It's usually a matter of either checking for the presence of voltage at a certain point, or doing a continuity (Ohm) check between two points to determine if the path is damaged. If you have a multimeter (under $5 at Harbor Freight) you can pretty much troubleshoot your entire car. Electrical diagrams are a simple matter of following the path as it goes through the circuit, noting wiring color changes, and what it passes through on its path. If you have a failure in a circuit, tracing it with the multimeter through the path will lead you to the problem.

micktroup2

Thank you so much for the advise! I am a novice at wiring... My engine appears to only have the strap from the back of the passenger head to the firewall and the one from the battery to the same head. I don't see any on the other side. Should I add another to the drivers side head? There is a header bolt that is extra long that the alternator bracket mounts to that is a snap to get at- sound like a good place? Should I add more?

As to my problem- I have gone through three starters that have become heat soaked. If the engine was more than 160 per the gauge, it would not start. I just installed a mini starter from Summit that is supposed to cure that, but my mechanic mentioned a possible ground culprit, as opposed to a string of bad luck with starters!

Oh, and the strap from the engine to the firewall is new. The previous owner had one on there that had broken- instead of replacing it, he had just overlapped the ends and zip tied it together! That should do the trick!

I also have a short in the interior- my hatch release/interior lights/door lock/stereo fuse keeps blowing. Guess I am going to have to pull the dash too...

aliceempire

iTrader: (14)

heat soak? Are the headers or manifolds getting too hot? Maybe headers that run too close to the starter? I had a similar issue when my 92 was TBI and the tune was off and heated the headers enoungh to effect the starter. Is your car stock?

1983Chimaera

Heat increases resistance, so if you already had poor ground the extra heat from the engine compartment could be enough to prevent good current flow to the starter. I would definitely add ground straps so all 4 corners have good grounds, and your overall ohm reading between the block and chassis is less than 2 ohms.

micktroup2

I can not thank you enough for the advise! Poor electrical ground never seems like a 'sexy' answer to a muscle car problem, but it appears in my case it may be! I took your advise and raced over to the nearest Pep Boys and grabbed their last ground strap. I asked one of the techs 'can you have too many ground straps on an engine' and he responded 'no such thing as too many!' He then went on to tell me that he had seen a 14% increase in horsepower on a dyno run, just by adding extra grounds. Now, that could be a load of rubbish, but I did notice something when I added the extra ground... I mounted it on the front of the drivers side head and connected it to the chassis under a nearby fuel line clamp(after sanding the paint off under the bracket). And I noticed something extraudinary- it cured my erratic tach!
My tach has been bouncing around for the longest time, to the point where I just had a bad connection behind the cluster. But as soon as I added that ground strap, the thing is rock steady and ACCURATE for a change!

Does that make sense- and should I add a couple MORE??

1983Chimaera

Definitely. And his claim makes sense. Any extra strain on the electrical system, I.E. the alternator, is more work the engine is having to do besides moving the car. So by lowering the amount of resistance in the system, thereby making the alternator's job easier and less work the engine is having to do means more freed up hp.

Go to Harbor Freight and pick up one of their $2.99 multimeters. It's just as important a tool to have in your muscle car toolbox as any wrench or socket set.

1983Chimaera

One other note. NEVER paint a ground strap. Electrons travel on the surface of wiring, not through it. This is why stranded wire carries more current than a solid wire of the same gauge, the stranded wire has more total surface area. The larger a wire, the more surface area, the more current it can safely carry. The reason a wire feels hot to the touch when it is too small for a current is the resistance created by the "backup" of electrons trying to flow along it. This is also why you were most likely having problems with your starter, the extra heat of the engine compartment added to the already excessive resistance due to poor grounding and wouldn't allow enough current to flow. This also means if you paint the ground straps, since the paint is not a conductor of electricity, will effectively neutralize the effectiveness of the ground strap. That's why I had you scrape/sand the paint from the point where you attached the ground strap to the chassis as well.

jermdm

I added a couple grounds on my iroc. 1 from battery neg. to the body and the other on the engine to the body. I used 4 gauge ground cable that you can buy from any auto parts store. Nice thing is that the ring lugs are already attached to the cables. Just measure the lengths that you need and go to the battery cable section at you local auto parts store and get the ones that closely match your measurements. I'm still wanting to upgrade my alternator charging wire also. The one that goes from the back of the alternator to the battery. Always a good idea.

micktroup2

While I am seated here at the feet of the masters, learning how little I know about cars, could that extra ground have cured my tach problems and could a poor ground translate to other electrical problems such as my door lock fuse blowing??

1983Chimaera

Those and any other number of problems. As well as the age of our cars, various levels of abuse and exposure to various extreme climates. Frayed/baked wiring can lead to shorts (the usual suspect for blown fuses), excessive resistance can lead to melted insulator (which in turn leads to shorts), years of rubbing against various edges throughout the car also leads to such problems. Everyone always checks all the mechanicals of their car, but no one ever thinks to check their wiring. Which is a shame, since electrical gremlins are the source of most daily driver problems and are the hardest to troubleshoot.

jermdm

Having good grounds can make you tach work correctly and alot of other things. I had all good grounds in my engine compartment but still had issues with my temp gauge, volt gauge and dash lights. I removed the gauge cluster and cleaned every contact on the printed circuit board plus the 2 connectors that plug into the cluster and that fixed my gauge problems. If your door lock fuse is blowing, you have a short somewhere in the circuit. Does the fuse blow when you put new one in or does it blow when you operate the locks?

1983Chimaera

Right. If it blows as soon as a new fuse is put in, it has a bare spot shorted to ground somewhere. If it shorts only when you try to use it, it has a problem with the switch or control module. This is one of those "need a multimeter" times.

micktroup2

Two comments, on blown fuse and melted insulation: 1) blown fuse- it doesn't blow when I put it in, or when I use a specific switch. It works fine for a while. Then I will just notice that the dome light didn't work when I opened the door and the fuse has gone. I imagine a gradual buildup in resistance until the fuse can't cope...2) melted insulation: when I had to have my mechanic replace the starter(last stock size behemoth before I switched to the mini-starter) the lead from the battery to the starter was BARE WIRE WITH INSULATION DRIPPING OFF IT!!!! Do YA THINK that bad ground was an issue??

1983Chimaera

Issue 1:

Harder to trace. Easiest method for you would be to put in a new fuse, and disconnect one part of the circuit at a time, waiting until the fuse blows each time before you pull the next item. If you get back to the fuse box and it still blows fuses, start checking the wiring itself for a bad spot.

Issue 2:

Melted insulation is a sign of one of two things; Wiring too close to an excessive heat source (header, manifold, etc), and if that's not the case then excessive current draw or resistance. Given your ground issues, I would guess the latter.

micktroup2

And that battery to starter cable was 6 MONTHS OLD!!

1983Chimaera

I think those ground straps are less than $10 each? An ounce of prevention...

micktroup2

The insulation wasn't melted in one spot- it was dripping off the entire cable. I will swing by and see if it is still at my mechanics- it was yesterday... Post a photo for your amusement!

jermdm

Since the fuse doesnt blow when first put it in and everything works for a period of time, means you dont have a dead short to ground. Most likely you dont have a power door lock issue. Could be a dome light issue. It doesnt work when the locks arent working. Need to know what else this fuse powers and it will give you an idea where or what the problem is.

1983Chimaera

Gimme a sec, I have my Haynes handy

1983Chimaera

Ok...Accessory fuse (20 Amp) supplies the following items;

Acc fuse supplies 12V Hot At All Times via Orange wire to
- Glove Box Light
- Left Courtesy Light
- Right Courtesy Light
- Map Lights

Glove Box Light continues to ground. Left Courtesy Light, Right Courtesy Light, and Map Lights continue on via White wire to Left Door Jamb Switch, Right Door Jamb Switch, and the Courtesy Light Switch (all three continue to ground).

Acc fuse also supplies 12V Hot At All Times via an Orange wire to the Left Door Lock Switch and Right Door Lock Switch, which continue on thru both Light Blue wires and Black wires to the Door Lock Relay Assembly, which in turn activate the relays to operate the door solenoids.

Acc fuse also provides 12V Hot At All Times to the stereo system. An Orange wire provides clock power to the clock in the base stereo system, and power to the Amplifier Relay in the Delco-Bose stereo system.

1983Chimaera

Typically a bulb won't cause a fuse to pop, unless the wrong one is in the system (overtaxes the system). I'm thinking intermittent door jamb switch problem, or problem in one of the two light switches (Courtesy Light Switch or Map Light Switch). Not much else in the circuit, unless the stereo is the cause.

micktroup2

The stereo is currently not hooked up- the PO had it installed with twist connections and electrical tape(!)- I just installed a replacement stock pigtail so I can install whatever stereo I want. The fuse covers: hatch release, stereo, mirrors, dome lights and door locks. I have disconnected the hatch and the mirror in turn- still blows.

1983Chimaera

Check the bulbs, make sure there isn't a wrong one in there somewhere drawing too much current.

TreeFiddy

A common cause of the ACC fuse blowing is the cigarette lighter, either broken or something metal jammed in it.

The car only needs two main grounds. One big one from batt to engine, to handle starter current. And one from either batt or engine to chassis, to power the rest of the car. Throwing more grounds at it is just covering up some bad connection with one or both of the main two, but may provide a measure of 'backup' I guess.

You can paint a braided ground any colour you like; just as long as the connection points are clean bare metal. BUT the paint will probably flake off easy due to being flexed, which is probably why you wouldn't bother.

micktroup2

Well Treefiddy, I respectfully disagree, me old mate. It has a new ground from battery to engine and from battery to chassis. If that was all that it needed, it wouldn't also have one from the rear passenger head to the firewall.
Once I added the second ground to the other head, my tach returned to normal- weird.
Anyway, I think my dome light is the culprit. I pulled the bulb yesterday and replaced the fuse and everything is still working like it should although I have not installed the stereo... The reading lights under the mirror come on when I open the door and turn the headlight switch, so I am guessing it is not the switch on that circuit. Any ideas on what is bothering the dome light before I pull out the headliner(!)?

TreeFiddy

That's cool However to function - any particular circuit on the car doesn't really care about the path the current takes back to the battery terminal, so long as there is one. That's going to be via either the chassis or the engine block - as long as these two are solidly connected to batt (-), that's all that's needed.

If adding extra grounds solves some problem, it implies a fault with the original engine or chassis grounding. But w/e, fixed is fixed

micktroup2

Well, I THOUGHT it was the dome light...! Two days and everything is hunky dory and BAM the fuse blows... AGAIN.
Looks like I have intermittent ground. God, I hate electrics!

1983Chimaera

Sounds like a bare spot on a wire somewhere. Probably is only causing it whenever you hit a bump just right for it to make contact. Check the dome light wiring first, trace along looking for cracks or other spots were the insulation has been worn away or damaged. Visual checks are your best friend here.

maverickfl

This is an old post that came up as I was researching some related information. Just wanted to correct a misstatement here since much of the information given was good.

The 'skin effect' you are referring to, electrons moving closer to the surface of the wire only applies to AC current, not DC current. Electrons will travel evenly through wire utilizing DC current. It is perfectly fine to paint surfaces carrying a ground provided it is not the contact point for the ground. The paint does not conduct/transfer well, so terminals should always be mated to bare metal surfaces.

Arts89Iroc

1983Chimaera, what size of ground straps did you use? width in particular? Thanks

Art

Tibo

iTrader: (15)

I believe that the stock size ground straps are 10 gauge. You can search ebay and find ground straps up to 1/0 gauge. You do not need to stick with grounding straps exclusively, plain ol wire will work fine. Braided straps are used because they will withstand more vibration and bending than normal wire. However, many of the engine electronics terminate their grounds via wire to the back of the head so wire is fine to use. When adding grounds try not to use the firewall as it is considered "noisy" as many interior devices terminate a ground to it. Stick to the frame rails and such. Fully welding the metal where only spot welds are used can also help with conductivity. Firewall, strut towers, frame rails, cowl, core support, the car is full of them. Using 1/0 wire to connect the driver/passenger sides of the frame together can also lower resistance.

TEDSgrad

iTrader: (4)

And if you have an e-tranny.