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Improving the primary ground (earth)

PostPosted: Sun Oct 19, 2014 3:50 am
by EnfoKen
My S2 has been generally problem free with the exception of the occasional grounding issue that causes slow or non starting issues. Over the years I've had to tighten the bolt that secures the ground cable through the body to the frame. It seems to be the main culprit for causing the car not start at least in the case of my car. The other night I went to go for a drive and nothing happened when I hit the key. While the head lights worked , the starter would turn the engine about one revolution but no more. The next morning I set out with some jumper cables and tried to start the car and again nothing. I then attached one cable to the negative side of the battery and attached the other end to the engine and bingo it turned over with ease and in fact high speed and started without issue. Of course this indicted to me the ground was the issue. I checked the ground cable from the battery to the frame and it seemed fine. I checked the short cable that spans the engine block to the frame and it was fine. One other telltale sign of the engine trying to find ground back to the battery was when the metal lead from the coolant temp sensor in the head touched the metal brake line (remember the car is LHD) and became glowing hot. Fortunately I spotted it in time before there was any damage. I spent nearly two hours searching for the possible issue without luck. So I decided to fix it once and for all. Once I thought about the solution, it seems so logical that I was sure it had already been done but I searched on this forum and did not find anything. I went to the auto parts store and purchase 60 inches of battery cable along with an 18 inch cable. First I replaced the short cable from the battery to the frame. I then ran the 60 inch cable long the bottom of the car attaching to the ground bolt at the battery and the other end to the bolt that holds the started in place. I am not kidding when I tell you this is probably the best thing I have ever done to the car. It starts without issue and the headlamps are even brighter. The cable is tucked up long the frame and secured with wire tires in a few places. I really can't think of any negative aspects to this other than it adds about 1 lbs to the car and it is not original . While I felt a bit defeated at first, the improvement was great and I continue to drive the Elan on a regular basis.
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Re: Improving the primary ground (earth)

PostPosted: Sun Oct 19, 2014 8:12 am
by TroonSprint
Yep. You've got have good earthing (grounding). I have run twin earth cables from the battery to the top body bolts on the rear suspension turrets. The advantage of those bolts is that they are tapped into the metal of the chassis, and not just clamped against it. I also have an earth braid around both engine mounts. But your solution is even better!

Re: Improving the primary ground (earth)

PostPosted: Sun Oct 19, 2014 8:13 am
by Elanintheforest
Good and simple fix, Ken!

Where was your earth between the engine and chassis before? There is usually an earth attached to the chassis side of the engine mounting, from the engine side of the engine mounting, but that is often partially insulated by paint on the mount or chassis, or rust / crud build up over the years, so doesn't work properly.

I had the same Eureka moment by putting a hole in the chassis next to the mounting and fixing the earth to that, once the paint had been removed of course.Having that work depends entirely on the battery earth being sound as well!


Re: Improving the primary ground (earth)

PostPosted: Sun Oct 19, 2014 8:33 am
by PeterK
Like Mike, I also have my main battery earth connected to the rear upright chassis leg. For the engine, I've run my earth from the starter bolt (like you) to the front upright bolt.
Both my main earths are actually higher capacity cable than the main feed (welding cable).

Re: Improving the primary ground (earth)

PostPosted: Sun Oct 19, 2014 8:28 pm
by RichardHawkins
Thanks for the post.

My car is not complete, but I am doing the same as you, running a separate earth (ground) to the starter. Thanks for confirming that it is a good alteration.

Richard Hawkins

Re: Improving the primary ground (earth)

PostPosted: Sun Oct 19, 2014 10:39 pm
by cal44
Yep, what PeterK wrote. Welding cable. Very flexable, tough exterior. Crimp (use proper crimp tool, not your vice) and solder lugs, no dirt or moisture gets in. If you want to the extra mile (for you rainy day guys) put heat shrink on the lug and cable connection area(underground utility quality heat shrink) with an overlap of about one inch or a touch more. Although heat shrink tubing may be to thick for some applications.

Re: Improving the primary ground (earth)

PostPosted: Mon Oct 20, 2014 4:10 pm
by Higs
I would suggest the following as the simplest solution with least "non originality".

Earth the battery to one of rear turret bolts (dry and uses a bolt screwed into the chassis)

Earth the engine from the engine mounting bolt to the front suspension/chassis bolt (not quite so dry but uses a bolt)

The first needs a 36" cable for a plus 2 and the latter a 15"cable.

Problem solved and visually quite standard.

Goodness knows why Lotus chose to use bolts that were not tapped into the metal chassis. As everyone points out, using nut and bolts requires the paint on the chassis to be removed and then not to corrode.


Re: Improving the primary ground (earth)

PostPosted: Tue Oct 28, 2014 11:42 pm
by Sea Ranch
I'm afraid I'm with Richard (Higs) here.

Any method is sufficient, as long as the contacts are kept clean and tight. Theoretically, the chassis is enough conductor, without extra cabling. Any "new" method/path will fail like the factory setup, once the contact/connection points become corroded/loose.

But it IS thrilling, I agree, when you see the effect of a truly good ground.

What about the windows, those of us with electric lifts? Good solutions there? They REALLY need solid ground of decent capacity.


Re: Improving the primary ground (earth)

PostPosted: Wed Oct 29, 2014 4:58 am
by reb53
And....if you're still using the earthing point in the floor of the boot then run a drill through the bobbin and remove the threads.
Otherwise you're tightening the earth down onto a bobbin, ( set in fibreglass), with no good guarantee of the connection to the chassis underneath.
If you drill out the threads you'll get a good clamping action right through bobbin and chassis.
In the early days of owning my car this fixed lots of intermittent problems.


Re: Improving the primary ground (earth)

PostPosted: Wed Oct 29, 2014 6:09 am
by Sea Ranch
Brilliant solution, Ralph, IMHO. Solves/eliminates the difficult two person task of keeping the bolt tight from underneath while cranking down on the nut from inside the boot. :mrgreen: :mrgreen: