ECU box ground.

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68383GTS

68383GTS

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Getting ready to convert my lean burn to a 70's style electronic ignition. I have done this conversation in the past a few times eliminating points. I have always grounded my ECM to the fender well or firewall. I was thinking this time grounding it straight to the battery.Would there be any issues grounding it straight to the negative side of the battery? Or maybe grounding it to the inner fender and the battery?
 
I can think of none. I mounted mine on the passenger's inner fender up in the corner next to the firewall and ran a ground wire over to where the factory engine ground attaches to the firewall, but I see nothing wrong with going right to the battery.
 
Bewy said:
It won't cause a problem but will add a wire that is unnecessary.
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Says who? Between the paint on the box, paint on the car....the joints of the panels, oxidation and on and on. That "extra" ground wire is good insurance.
 
I see nothing wrong with an added ground. While you are at it check your charging/ running voltage. Two issues "usually" plague these girls. 1, mostly harness voltage drop to the VR causes overcharge. 2, sometimes the VR ground. "A good plan" is to look at the pass side front of the head. Those holes are on the REAR of the driver side head. Use a short "eyelet to eyelet" starter cable, 12"--18" long, bolt to the head, and a good point on the firewall, the bolts mounting the master cylinder on manual brake cars is good.
 
You can I ran mine off the ground on the battery for a while then mounted it to the radiator support for a cleaner look.

Here is part one if your interested
 
Put star washers on the mounting bolts. Those “bite” into the metal on both parts & make for a good ground.
 
Either way your best friend here.
grounding brush.jpg
 
dartfreak75 said:
Wish I had one of them when I done mine I jacked my paint up trying to get a good clean ground surface.
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Those do look handy as hell! I just made one out of a small screw, washer, coupling nut and a piece of 80 grit sandpaper. I had no idea they made such a thing!
 
A person can always implement a floating ground type system with buss bars at wherever on the vehicle you need grounding points and do it that way, also you can hide the bars so they aren't out in the open.
 
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mopowers said:
Those do look handy as hell! I just made one out of a small screw, washer, coupling nut and a piece of 80 grit sandpaper. I had no idea they made such a thing!
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Me either thats smart how you made yours i wish I would have thought of that I used one of those mini flap discs on a air grinder. It messed my paint up im gonna have to go back and touch it up
 
If battery cable ground to engine fails, the smaller ECU ground at battery will attempt to carry starting current, and smoke, perhaps a fire. Rare, but it has happened.
 
IMO; a grounding wire is a waste of time.
But I did BOLT my box to the apron when I was using those.
If you run a separate wire, you still have the exact same problem area; before you installed the wire, it was box to apron/firewall; after the wire, it is box to wire; no difference unless you weld the wire to the box. Just make sure your passenger head is grounded to the firewall and you will be fine.

For a long time, I had two of them bolted to the apron, so I could just swap boxes in a few seconds; then replace the faulty one after I got home.
 
It is a waste of time...& cable. Mopar inner fenders are spot welded to the f/wall, sub chassis. We are talking about 6 amps [ max], not 300-500 for the starter. There is enough 'connection' there for a more than adequate grd through the welds. Make sure the metal is clean on the box & mating surface on the fender, use a star washer between box & fender, job done.
If you were to extend this separate grd cable to the battery neg logic , then you would have grd cables from the h/lights [ about 15 amp for 4 hl car ] & one from the cigar lighter, p/windows etc. You DO need to make sure that the grd cable from engine to the body is of adequate CSA & has clean connections at each end.
 
It's my damned car. I'll waste my time if I want to.
 
Bewy said:
It is a waste of time...& cable. Mopar inner fenders are spot welded to the f/wall, sub chassis. We are talking about 6 amps [ max], not 300-500 for the starter. There is enough 'connection' there for a more than adequate grd through the welds. Make sure the metal is clean on the box & mating surface on the fender, use a star washer between box & fender, job done.
If you were to extend this separate grd cable to the battery neg logic , then you would have grd cables from the h/lights [ about 15 amp for 4 hl car ] & one from the cigar lighter, p/windows etc. You DO need to make sure that the grd cable from engine to the body is of adequate CSA & has clean connections at each end.
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I gotta disagree with you on 2 things. The first is you don't want to put the star washer between the box and the fender because you are spacing the box away from the fender the thickness of the washer thus loosing surface area to ground too. And there is no twisting action in that location. The twist of the bolt is what spins the star washer and causes it to dig in. I put the star washers on both sides one between the bolt and ecu and one on the back side of the fender between the fender and nut. You don't want to separate the ecu from the fender by putting a washer in between the two. The other thing is the ground wire it dont hurt a thing to ground it with a second ground wire. It takes 5 mins if that is a waste of time your in the wrong hobby lol.
 
Dartfreak,
Whatever. The idea of compressing a star washer between two surfaces is to force the sharp edges of the SW to bite into the metal for good electrical contact. Use as many grd wires as you like. I am simply saying they are not necessary electrically if a good grd connection has been made as described above.
 
Bewy said:
Dartfreak,
Whatever. The idea of compressing a star washer between two surfaces is to force the sharp edges of the SW to bite into the metal for good electrical contact. Use as many grd wires as you like. I am simply saying they are not necessary electrically if a good grd connection has been made as described above.
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Im sure it would work either way. You may be right it does work better with the washer between but in my mind seems like more surface area making contact with the fender would be a more secure ground. Just a friendly debate im not arguing or anything
 
Floating ground system works better and is 10 times nicer looking but whatever, keep doing things how you guys want to do them and keep having problems, LOL
 
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