gsmithrx7

Hi everyone,
While reading Aaron Cake's article on proper grounding techniques for rotary engines I came across this picture.


This shows the ground connection, it makes sense to bolt it to an otherwise unused bolt hole

Here is a picture from my 88 manual


This diagram is for a Turbo, I have a N/A.

It shows the ground wire bolting through the rat's nest attachment point to the top of the rotor housing.

Arron states that this ground wire moves to different places due to service, but as long as the connection is clean & tight it is not a problem.

My question is: Does connecting the ground using the rat's nest bolt hole make any improvements in the overall grounding system? That bracket does bolt to the dynamic chamber. And the rat's nest bolts to the lower intake manifold.

I wondered what the two ground wires went to.

One wire grounds the EGI control unit (pin 3G)
The other ground goes to pin 3A but branches to the fuel pump circuit terminal (EM-30) ground
Also, to EM-31 which is the Engine control unit ground.

So, this one connection grounds three different electrical parts!

What do you think?
Thanks

Jeff76

I really appreciate your tenacity with your rebuild. Being an original owner and the first rebuild is quite the undertaking.

As for the grounding, the procedure is kind of been a bible for many. The work within these forums has been extremely valuable to many. Engineering for cars and telecommunications are different things. I came up in telecom. Some of the procedures here are not quite up to par for Telecom. Telecom assumes connections are good for 20+ years. Automotive applications have no need for such extreme situations.

I have read about this engine ground documentation as I have had the 3800 rpm hesitation many years ago. Since this seems to be the main engine gound, any connection to the "keg" section should be failry sufficient for grounding the engine. The process to do this will be different between disciplines. I advise using a thin coat of No-ox ID on every connection. On the lug, bolt and on the connection surface.

First... Clean the lug and the connection with a scotch bright pad... Then a light coat of no-ox on the mating surface and both sides of the lug. For extra help on the screw or bolt side of the lug add a star washer. This will increase the connection between the bolt/screw and the lug.
​​​​​​If you are worried about grounding between other devices, the ground is only as good as the connection between mounting surfaces and ground. That means.... Scotchbright, no-ox and a star at every connection. If you can not have the best connection between mounting surfaces as listed above... add a wire between the components that don't have a proper mounting surface. The wire gauge will depend on many factors. I am not that smart enough to recommend the formulas for the wire gauge with current draws, etc. Also, when adding a lug, add a light coating of no-ox on the wire before crimping the wire to ensure the connection between the wire and the lug won't corrode.

I know that this does not directly address the solenoid situation. However, the process of grounding that was laid out earlier(not so greatly) should be a some help.
Edit: if you are concerned about connections between point A and B.... a digital multimeter set to ohms will confirm the effectiveness of your connections. I am am not sure of the exact tolerances. As close to zero as possible is ideal.
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j9fd3s

iTrader: (3)

the solenoid rack usually has a little stopper on it, so that you can tighten the bolt without the wire spinning

WondrousBread

Back when I had the stock ECU I found that it didn't particularly care where the main ECU ground was on the engine, as long as it was a solid connection and there were no additional grounds. Aaron also mentions you shouldn't add additional grounds except the pressure sensor one for certain situations, and I agree. I found extra grounds made things worse. I never really determined why, but it seems clear the ECU really likes having all sensors ground in the exact same place.

I don't use any star washers on mine, but the advice that Jeff gave is good. I've had good results using a similar process which is to clean, add dielectric grease (I actually use one called Ox-Gard, IIRC) to prevent corrosion, and then firmly tighten the bolt. I also smear a little dielectric grease on top of the bolt / ring to coat it. Probably doesn't matter but grease is cheap.

Things are different now since I don't use the stock ECU but I always follow the same procedure with any ground I make and I've never had an issue with any of them.

One other thing to keep in mind is the resistance in the multimeter probes. One time I kept trying to track down why there were 0.2 Ohms of resistance in my ground path, and I ended up realizing the resistance was in the multimeter probes themselves. Test by just checking resistance with the probes touching one another, then write that number down and subtract it from any reading you take on the vehicle.

I'm sure there is a tolerance like Jeff mentioned, but in my experience a good ground should read 0 ohms on the multimeter. A more sensitive meter might show .05 Ohms or something, but an indicated 0 has been good enough in my experience.

Jeff76

Thank you for the correction and clarification. Adding extra wire can definitely cause many issues, ground loops are one of them. I was considering editing my post today to mention that but decided not to.

​​​​​​The sensor ground thing is not something that would have come to my mind. Now that I read about it. This does make a lot of sense. Having the same resistance to ground for all sensors seems like a very logical thing to do.

​​​​I could swear that some member mentioned that adding a rather large piece of wire from the engine to the firewall helped with some issues. I suppose if all other grounds were properly wired, this would have done nothing.

gsmithrx7

Yes, I see it, it is where the support bracket is welded to the metal lines.
I will be using this location. I just ordered some "NO-OX-ID "A-SPECIAL Electrical Grade" to use on all the grounds!

Thanks everyone for the help. I don't know how I would proceed without this forum!

j9fd3s

iTrader: (3)

the Japanese tuners like to use grounding kits. i recently translated an article about what they ground, and Xavier Borg, the fellow who is making the tuning software for the Power FC's added the why.
the why: things are grounded to the body, and then to the battery. the body being made of many pieces has a lot of capacitance, so things that have a steady current, like a bulb, are fine, but things that pulse, like injectors and coils can benefit from a lower impedance connection. also why these kits use big wires, they aren't really carrying current, they facilitate the pulsing of the circuit

the What: so this sensor ground gets grounded, the firewall ground, and the ignitors (it also says knock sensor, but i think its not translated correctly) sometimes they have one on the alternator. Revolution goes a step further and has a shield on the spark plug wires, and that gets grounded too, in fact the plug wires and grounding kit come in one box, which is pretty smart.

i did just do it on my car, but i did a bunch of other things at once so i don't know what it did. it also didn't seem to have a downside, so there is that too

gsmithrx7

Hi everyone,
I am in the process of cleaning up the engine bay, the drivers side is the worst!

I have found four ground connections in the bay, there is one behind the passenger side headlight, where the windshield washer reservoir neck is attached to the reservoir.
Then there is the one on the firewall (why do they call it a firewall!?), from the AM antenna in the windshield to the top of the transmission.
Next is the connector on the driver's side shock tower that grounds five separate wires! It is below the trailing coils.
The most important one is the battery ground cable to the same shock tower!

I am cleaning the bolt holes out, after screwing the wire brushed bolt in and out until it moves freely. Some mineral spirits on a Q-tip until it comes out clean.
Then applying some of that great conductive grease to the bolt and hole.
I cleaned the lug with a wire brush, this removed most of the copper plating down to the brass, but so it goes.
More conductive grease (not dielectric grease!) on the lug. Then assemble the connection not too tightly, snug will do.

Along with the engine ground have I missed any other grounds in the engine bay?
With everything out of the way, now is the time to clean them.

I need to research into adding that sensor ground wire, it seems important to do.

Thanks everyone for the help!

Jeff76

To answer the question about the firewall... I believe that engine fires were common enough to enhance the protection to passengers and driver from engine fires.

​​​​​​As for the drivers side engine bay, space there is very tight. I was working around there lately and see why people tear out the power steering and air conditioning. I will try my best to resist pulling these out.

I really don't want to needlessly complicate things with grounding. I would like to say though, when I did Telecom work, grounding just through screws was not an acceptable work practice. Paint needed to be removed as well. The increased surface area that the lug was in contact with on the mating surface is manditory in some applications. You can decide for yourself. What is not optional is some sort corrosion protection.

This is the ground on the shock tower for the five grounds. This was after cleaning off the very thin coating of no-ox. This scraped paint was done 20 years ago. The bare metal is completely clean! Use protection....

Not only did the lug get cleaned and protected but the female side of the plug was spray cleaned and the male pins were cleaned with scotch bright and no-ox was lightly applied. Every DC voltage connection in the car that isn't connected with solder will benefit from a good cleaning and some protection.

gsmithrx7

Well said! I will be removing both the Leading & Trailing coils to get at the brackets and bolts in a few minutes. Your picture shows the two bracket bolts I will be dealing with.

Your statement about only bolts making the ground connection is important, and your picture shows that if you go through the hassle now, you will not have as many problems with your connections later on.

These connections aren't gettin any younger!



Thanks again!

gsmithrx7

Hi again,
I removed the two brackets for the trailing coil and the three nuts holding the leading coil to the fender well.

Here is a picture of the trailing coil rear bracket



This rubber mount is the same one used on the A/C line on the fire wall!

All that I can come up with is some kind of vibration dampener.

That being said, the bolt does go through the entire length and will make a good ground connection?

I will treat it as such and go through the process of cleaning it up and putting my electrical grease on it.

What do you think?

gsmithrx7

After removing the leading coil I am left with the three bolts that attach to the fender well.

I will wire brush these and the attaching nuts to get a metal to metal connection.

I have electrical grease the is electrically conductive, not like di-electrical grease! This I will put on the bolts and nuts when I re-attach the coil.

Your input is appreciated.

Jeff76

There is another mount on the coil, as long as at least one is tide to the mounting stud on the wheel well, it should be good. If there is a way to make what is there even better... great.

gsmithrx7

Just to prove me wrong, here is a picture of the mentioned insulator bolt thingy. My car is out to get me!



I went to remove it and it separated, so this connection is not a grounding one!
Nice to know going forward.

Thanks again for all your replies!

I am now going to do battle once again with my engine bay. The passenger side hates the driver's side, she has gone out of her way to destroy it!
My weaponry is rust reformer & epoxy paint, I never give up, "All The Way!"

Jeff76

As I tried to say earlier and failed. As long as one mount is tied to the firewall, it's good.

If you have a multimeter, check for continuity from the battery ground or chassis and the screw you are hoping to have a good ground. It should be close to zero after zeroing out the meter.

Keep at the rust work. Some sanding, treating and painting is what I am doing where needed. It is certainly better than spray and pray. Mine is a bit chewed up on the front driver side, like yours is.

gsmithrx7

Thanks again,
I now have some idea what goes into a proper ground connection for the long haul!

The conductive electrical grease makes all the difference, and the fact that just the bolt thread connection is not the best way to make the ground connection is enlightening!

For the trailing coil ground connection, I have sanded through the paint on the shock tower to bare metal, also sanded the mating surface of the mounting bracket to bare metal. I will apply the grease to both surfaces then attach it with the bolts. The two studs on the bracket will be wire brushed to bare metal also to assure the ground connection is good. A bit of effort, but I think on a 35 year old car it is the way to go.

What do you think?

Jeff76

If you want to do it, it isn't going the hurt anything, as far as I know. It is a little overboard though. When I was having spark issues, I sanded an area where the coil touches the wheel well. However, I only sanded until I reached the grey/tan layer and stopped, thinking I was on metal. 😆

gsmithrx7

Thanks, all the bolts that attach the brackets to the sheet metal of the engine bay are the self-tapping kind, used to scrape out some of the paint that coated the inside of the boltholes when the chassis was dipped into the primer and paint at the factory. This bolt connection was sufficient for a good ground when the car was new. But now, some of the bolt threads are corroded and need to be cleaned to bare metal for them to make a good ground again.

It will be a bit of work to clean all the parts and make sure I have a metal-to-metal connection on them.
I can then not worry about these grounds when I start chasing my electrical gremlins around.
I don't want to even think about digging around the engine bay once I get the engine back in.

I will be using the electrical grease even if the connection is not a ground, I was going to anti-seize lube but the grease is better.

The person who gets my car will sing praises about me!

I'm off to do a little more painting in the bay, it is starting not to look like a rust bucket so much.