Poor main earth connection

Technical advice Q&A
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ChrisC
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#1 Poor main earth connection

Post by ChrisC » Thu Mar 21, 2019 12:46 pm

Chaps,

The answer to this eludes me...

Sometimes, I try to start the car and it *appears* that the battery is totally flat and I mean totally - not even the panel lights work. However if I undo the battery earth lead from the bulkhead and then reconnect it, the car starts and runs just like you would expect. Clearly I have a intermittent bad earth.

I have over time, removed the standard bolt and replaced it with a brass one, replaced the earth lead with a new one, cleaned the terminals I don't know how many times, tried brass washers, I have even sanded the bulkhead back to bare metal, bolted it all back together and liberally coated the connection with lithium grease. However I still don't seem to have permanently solved the issue and on occasion I will have to remove/replace the lead to get the old girl running.

Does anyone have any smart ideas, does high conductivity grease exist which might stop the connections corroding?

:thankyouyellow:
1964 FHC 4.2
My Etype restoration progress www.connor.org.uk

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MSM
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#2 Re: Poor main earth connection

Post by MSM » Thu Mar 21, 2019 1:34 pm

Chris

With the amount of time you have spent on the earth lead it is probably now fault free.

What about the other battery connection? Or it's connection to the main stud under the heater box? What about the connections on either end of the lead from the stud to the starter? There is also a flexible earth lead under the car on the exhaust side adjacent to the reaction plate - worth a look.

Good luck.
Mike

S2 FHC

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abowie
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#3 Re: Poor main earth connection

Post by abowie » Thu Mar 21, 2019 10:42 pm

MSM wrote:
Thu Mar 21, 2019 1:34 pm
Chris

With the amount of time you have spent on the earth lead it is probably now fault free.

This was my feeling when reading the original post as well. I've seen some pretty shitty rusted frayed engine earth leads and they all seemed to work.
Andrew.
881824, 1E21538. 889457..oops
http://www.projectetype.com/index.php/the-blog.html
Adelaide, Australia

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cactusman
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#4 Re: Poor main earth connection

Post by cactusman » Fri Mar 22, 2019 7:11 am

It is also possible that the fault is within the solenoid. Mine was sometimes very sluggish....other times ok. New solenoid (mine is not part of the starter) and the problem was gone.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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Simonpfhc
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#5 Re: Poor main earth connection

Post by Simonpfhc » Fri Mar 22, 2019 7:15 am

New battery time!
Simon
62 3.8 FHC
52 XK120 OTS
91 Porsche 928GT

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#6 Re: Poor main earth connection

Post by ChrisC » Sun Mar 24, 2019 5:32 pm

Thanks but no its won't be the solenoid, engine earth strap or the battery itself.

If I touch the battery earth strap too earth with a spanner I get a small spark - which implies its the connection on the bulkhead. Its almost as if the terminals are oxidising over preventing connectivity.

As I say, loosening the earth terminal on the bulkhead and then retightening it, means the car starts right away - even if before I do that, the battery appeared to be totally flat. I keep a battery conditioner on the battery so its always charged up.

It *is* a weird problem - hence the reach out to you guys as I am running out of ideas :)
1964 FHC 4.2
My Etype restoration progress www.connor.org.uk

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#7 Re: Poor main earth connection

Post by mgcjag » Sun Mar 24, 2019 5:57 pm

Hi Chris you mention if you touch the earth cable to earth you get a spark.......is this with everything turned off?.......also are you running positive earth......dont ask me the technicals but there is cathodic corrosion....possible since you changed to a brass bolt for the body connection....(dissimilar metals)...i know no more than that so dont try to shoot me down :bigrin: ...im just throwing something into the discussion.....Steve
PS dont know about Lithium grease....but silicone grease or Vaseline for electrical connections....
Steve
1969 S2 2+2 & Building a C type replica

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cactusman
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#8 Re: Poor main earth connection

Post by cactusman » Sun Mar 24, 2019 7:37 pm

If you are certain it is corrosion at the main earth then dismantle the termination, put a shamqe proof lock washer under the tab so it sits between the tab and the body. Plenty of Vaseline and tighten up. The washer will cut into the tab and the body and make a good electrical connection while preventing any loosening and hopefully the Vaseline will deter corrosion. Excess can be wiped away once tight.
Julian the E-type man
1962 FHC
1966 MGB....fab little car too

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#9 Re: Poor main earth connection

Post by ChrisC » Mon Mar 25, 2019 4:03 pm

Ive just been reading up on conductive grease, I sense a test session coming up tomorrow to see which one conducts electricity the best. Vaseline was mentioned but that's petrol based, but I can play with lithium, silicon and copper grease - I will report back :)
1964 FHC 4.2
My Etype restoration progress www.connor.org.uk

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