HappyFather
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| posted on 22/7/12 at 03:30 PM |
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How to track down bad earth?
Hello!
My question is "How to track down bad earth"? I have a multimetre but don't know how to use it. 
I'm pretty sure I have made a couple of mistakes working on the loom and would like to know how to track the mistakes down. It surely
can't be just based on visuals, right?
Thank you for any help!
HappyFather
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(for those that like the whole story)
In April I managed to start the engine for the first time. But I couldn't drive the car since it still had no brakes. I did not start the car
again since then.
Since then besides working on the breaks I made several changes to the electrics, mainly to wire up the dash. Today I got to a point where I can drive
the car inside the garage. It has no lights, still lots of the electrics undone, some stuff temporarily connected with tape or clamps. But I could
run. Tried to start the car and it failed.
- I believe that I connected the key barrel wiring incorrectly since I would get the starter engine rotating on my first move on the key (should only
happen on the second).
- I did not hear the fuel pump sucking fuel.
- During my several attempts, in the beginning the Digidash lit up but at a certain point stopped lighting up
- When I gave up, went to the battery to disconnect it and the box that has 2 30A fuses and connects on the positive was hot ('94 CBR 900
engine on carbs)
Given all this, I believe I have done a mistake on the key barrel. Besides that, I might have something badly connected or something that should be
earthed but it is not. A visual inspection to earths proved they were all connected to the chassis. So I need a more reliable way to find my mistakes.
Is there one?
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coyoteboy
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| posted on 23/7/12 at 12:37 PM |
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How many grounds do you have on the loom? Are you grounding components to the chassis at various locations or do you bring them all back to a few
central connector blocks?
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HappyFather
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| posted on 23/7/12 at 01:18 PM |
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The loom has two sets of wires that the instructions say are earths.
The one at the front is riveted to a chassis rail.
The one on the back is held temporarily with a plastic clamp against a chassis rail.
I also have
1) an earth wire from the oil pressure/temp connector to a chassis rail,
2) an earth wire from the water temp casing to a chassis rail and
3) an earth from the negative battery pole to a chassis rail.
All these are held to the rails temporarily with tape. I didn't scratch the powder coating on the rails where I taped these earths. Can the
paint prevent the earths from working as expected?
Thank you for your time and attention!
HappyFather
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RichardK
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| posted on 23/7/12 at 01:21 PM |
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Indeed the powder coat will prevent a good earth, so the coating needs to be removed, I welded on some bolts to my chassis in various points this
allowed me to bolt eyes down securely.
Cheers
Rich
Gallery updated 11/01/2011
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coyoteboy
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| posted on 23/7/12 at 01:49 PM |
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Indeed, all grounds need to connect to bare metal and be firmly clamped to it to operate properly. Any slight movement or surface coating can result
in a high resistance joint, best case nothing on that circuit works, worst case you can can damage other parts.
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steve m
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| posted on 23/7/12 at 04:05 PM |
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I can not answer your question directly, but when i made the last loom for my car, (and it will be the LAST one!!)
i wired in a brown wire as well, for earthing, this is perodicly screwed to the chassis, and each item that needs a seperate earth
It maybe overkill, and think of the weight of another wire  (for you bec boys)
But for my own satisification, i know were every earth point is, and can easily trace were each earth wire goes !
Steve
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Irony
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| posted on 23/7/12 at 04:13 PM |
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I am not a expert when it comes to electrics but I am learning fast. These are things that learn't so far that I think could help you.
Earth Points: There need to be as good as possible. Some locosters insist on welding the earth straps to the chassis. I didn't do this but
have used rivnuts and eyelets. You need good thick cables capable of carrying lots of current. You don't need the engine earthing back to the
chassis down the throttle cable or something.
Disconnect components: Make sure your components are disconnected before trying a circuit for the first time. I test for continuity before I connect
the battery and then I use a small bulb or buzzer in place of the fuel pump or headlight or indicator.
Buy a book: Complete kitcar do a good wiring book - cheap and it helps with fundamentals.
If you have a loom makes sure you understand each circuit before wiring it up. I wouldn't feel safe literally just connecting the marked ends
up and hoping it works. If the original manufacturer made a mistake and it proved dangerous you could have a bad day.
just my 2p worth
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HappyFather
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| posted on 24/7/12 at 06:33 AM |
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Thank you all for the suggestions to get my electrics right.
I bought the loom and it has eyelets on the earths to connect to chassis. I'll get the rear one on bare metal without powder coat to get it
right, even just temporarily.
I'll also test continuity and use the bulb test on the fuel pump. That will tell me if I need more fuel or not 
And until I get this right I better disconnect the Digidash... I just hope I haven't broken it yet.
Besides the fact that I really would love to drive the car, the garage is going to be washed next week and it would be wonderful if I could move the
car between washing days.
Tonight I'll go to the car and run some tests, I'll keep you posted. Thank you all once again!
HappyFather
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GOJO
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| posted on 24/7/12 at 09:20 AM |
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Check batt voltage across the battery, should be 12.2-12.7 ish ,then leave the pos meter lead connected and take the meter earth to your chassis
eyelets and you should have the same batt voltage at the earth points maybe 0.3 volt lower but then back probe the earths 2 " from the earth
eyelets to make sure the crimp or solder joint is good.
Rivets no good or rivnuts secure the earts with nut and bolt or tap a thread or use tare screws and serrated washers to make good contact
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HappyFather
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| posted on 24/7/12 at 11:08 PM |
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Hello all!
Just a small update.
Fixed the wiring to the ignition key barrel. Now when the key moves to 1st position the engine does not attempt to start. And the fuel pump gets
electricity, measured with the multimeter.
When I move the key to the 2nd position the starter motor spins but the engine does not start. After several attempts I drained the battery to a point
where the starter motor was moving slow.
Brought the battery home to leave it recharging for the night (and may leave trickle charging during tomorrow). Tomorrow I'll also get some more
litres of fuel, just in case it is an empty tank problem.
By the way, measured with the multimeter the feed on the earth eyelet and it was around 0,5v less than battery reading. But since I have the eyelet
riveted to the chassis, as stated above, that earth may still be bad.
Let's see what tomorrow brings
Thank you all for your help and advice.
HappyFather
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HappyFather
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| posted on 25/7/12 at 11:29 PM |
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And the problem is solved.
I'm so afraid of the quality of my electrics that I blame it without reason. The car lacked fuel... Added around 4 litres to the tank and the
car started.
Next weekend I'll attempt driving and, if successful, will post pictures or a movie.
Thank you all for the information shared. When I have all the electrics done I'm sure I'll have other issues and will use the information
from this thread again.
HappyFather
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