Powdercoating-gound issues

[Steve Wood]

I have been trying to help a guy for several months that had drivability issues.  It idled fine but would not run under boost and was getting worse.

Early on, I had him disconnect the cam sensor and it reportedly ran better.  Turned out there was a lot of up/down play in the shaft so he replaced the unit and the car ran good, but for only a few days.  Replaced other stuff, tried this, tried that.....car ran like crap.

He talked about taking it to KDK which I thought was a good idea.  Don't know if he did or not, but someone figured it out...He powdercoated the coil pack module bracket and that resulted in a bad ground.  Module did not like that.

I usually try to run a ground strap from the module to the firewall ground collection point and always try to clean up the contact points when I have the coil pack off....learned long ago that the bolts had to be tight to run right.

I also learned the powdercoat is not a good conductor when I did the alternator case on one of my cars.  Lost about 1.5v out of the alternator immediately but my meter figured it out fast....case was making a lousy ground with the bracket.

something to think about...always seems the basics will bite you in the butt

[earlbrown]

It also helps to be versed in the usage of a volt meter when chasing down voltage problems!! 

[Steve Wood]

I am tired of trying to teach people how to check voltage drops across a circuit...part icularly when they want to argue there is no voltage on the ground side and that I should be measuring the resistance to do it right

[earlbrown]

It truly amazes me how some people just can't learn simple simple circuits.

Years ago in my car stereo days I used to play hell trying to teach people series wiring..   and the fact that it will work.

The closest parallel I could think of was to ask "Have you ever wired up a flashlight?"


Here's a trick I use to try and get the un-wellversed looking for poor connections...   Have them clip the "red" to the "+" post and touch "black" to the "-" post  .....   Memorize what the number is.    Then use the negative probe to check potential bad grounds.   It normally confuses the hell out of the tester (and they don't learn nothin') but it makes absentee troubleshootin g a little more palatable.

[larrym]

All you guys did was confuse me..........

[Steve Wood]

Larry, if you put your meter on volts, touch one probe to the negative terminal of the battery (preferably not the cable terminal itself) and the other end to the engine block, and the meter reads 0.2v, then you know you have a two tenths drop within the cable or its terminals/connections.

If you put a probe on the alternator housing and one on the battery negative post and you get a 0.3v reading, you know you have lost three tenths of a volt somewhere between the alternator case and the negative post of the battery.

If you put a probe on the power terminal of the alternator and the other on the battery plus post, and it reads 0.1v, then you know you lost a tenth in that circuit.  Add the two together and you have a 0.4v loss in the alternator circuit between it and the battery.

Then you get to figure out where the loss was.  Alternator case connection to the bracket, ground cable, whatever....Pu t one probe on the case and one on the bracket, then engine, etc.

It is normal to have a little loss, but, a couple of tenths here, couple there, and pretty soon you are shorting yourself the voltage you need

[motorhead]

Larry, if you put your meter on volts, touch one probe to the negative terminal of the battery (preferably not the cable terminal itself) and the other end to the engine block, and the meter reads 0.2v, then you know you have a two tenths drop within the cable or its terminals/connections.

If you put a probe on the alternator housing and one on the battery negative post and you get a 0.3v reading, you know you have lost three tenths of a volt somewhere between the alternator case and the negative post of the battery.

If you put a probe on the power terminal of the alternator and the other on the battery plus post, and it reads 0.1v, then you know you lost a tenth in that circuit.  Add the two together and you have a 0.4v loss in the alternator circuit between it and the battery.

Then you get to figure out where the loss was.  Alternator case connection to the bracket, ground cable, whatever....Pu t one probe on the case and one on the bracket, then engine, etc.

It is normal to have a little loss, but, a couple of tenths here, couple there, and pretty soon you are shorting yourself the voltage you need

Adopt me, Steve. Seriously.

[Steve Wood]

I have too many guns.  You would probably kill me..

[Forzfed]

I had a chrome alt bracket which sucked as a ground also!

If you have multiple grounds on the same circuit you MUST have a common ground, or you could produce ground loops where stray voltages flow.

[tb3]

I had the same problem when I powdercoated the mounting bracket on my hot air years ago.
reading a meter is fortunetly one of the 3 things I'm good at in life and found the issue quickly.  like mentioned above, I just made a bonding jumper to a accessory bolt on the front of the motor since the coil pack is on the front of  motor on the hot airs. 
I could have just took a razor blade and removed the powder coat where any of the bolts touch the bracket to get my ground back, but the bonding jumper was easier.

[Steve Wood]

powdercoating can be tough to scrape off when put on well

For some reason, I have a hard time finding small, reasonably ground straps around here, but they can sure be handy sometimes

[tb3]

I found it handy to have a couple spools differant guage of bonding braid like found here  http://alliedboltinc.com/product/BONDING-BRAID-(25-FEET)~2525.aspx
that way I can cut to size whatever I'm working on.
some assorted connectors to bolt to what your jumping to is nice to have on hand, but most of this small stuff can be done with electrical connectors.
If I'm working with something where I'm worried about corrosion, I just heat shrink the braid before I crimp the ends
 

[Steve Wood]

that is a good idea!  thanks!

[SuperSix]

I got a spool at the Orlando HAMfest.

[larrym]

X 2 on adoption.

Your safe with the guns I'm an unarmed Canadian!