Need help. Engine Ground Straps

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Ronnie Wilson
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Joined: Fri Nov 18, 2016 11:40 pm
Location: Liverpool uk

Need help. Engine Ground Straps

Post by Ronnie Wilson »

Hi Guys

Does a 1986 uk Car require a Ground On the rear of the Cylinder Head above the Starter Motor and one from the rear of the Cam Cover Fixing Bolt to the Firewall. If yes then where would the other end of the Cylinder Head Ground connect to. The one on the Cam Cover to the Firewall is straight forward.
Can you get these Straps from Bmw if so do you know the part numbers.
Engine has always idled lumpy so was looking through the Bentley Manual and it put the lack of good grounding down as a possibility for poor idle.
Ronnie
Liverpool uk.
1986 635csi.
Bronze Beige Metallic.
bpoliakoff
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Re: Need help. Engine Ground Straps

Post by bpoliakoff »

All it is is a piece of braided flat cable with a crimped eyelet at each end nothing special. Any 14 0r 12 gauge wire will work
81 Euro 635 M90 with motronic. Currently under a complete nut and bolt restoration. Pictures at
flickr.com/photos/bertsphotos.
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Brucey
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Re: Need help. Engine Ground Straps

Post by Brucey »

I think the answer is 'probably not', as it applies to motronic models manufactured from mid 1980 until 6/87. The reason I say this is that there is a large earth strap connecting the engine to the body, without which the starter motor won't turn. Making sure that the earths (see ETM for locations) are all in good shape is a good idea anyway.

The rocker (valve) cover, cylinder head and inlet manifold are all well-grounded to the block by the various braces, fastenings etc onto the inlet manifold.

On those cars that do have an earth strap I wonder if it is there because otherwise there is a small chance of something going 'floaty' with the HT leads trailing about the place. I note that later chrome bumper cars have a (necessary IMHO) earth strap onto the airbox; this isn't otherwise grounded in any way and has the king lead mounted to it in two places....

cheers
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Ronnie Wilson
Posts: 239
Joined: Fri Nov 18, 2016 11:40 pm
Location: Liverpool uk

Re: Need help. Engine Ground Straps

Post by Ronnie Wilson »

Thanks Brucy.

I was hoping you would say it needs those Ground Straps solving my poor idle.
My Car is the Chrome Bumper Car. I’ll probably check and clean the existing Ground Straps then check the Fuel Delivery rate then the injectors. I have checked and changed the vacuum hoses, Fuel Tank, Fuel Cap and Oil Filler Cap every little thing i’ve done so far has made little differences to the better running of the Car. Thanks the quest continues. Cheers Brucy.
Ronnie
Liverpool uk.
1986 635csi.
Bronze Beige Metallic.
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Brucey
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Re: Need help. Engine Ground Straps

Post by Brucey »

in fairness you can make a flying ground lead and try it in various places to see if it makes a difference or not. I suspect it won't make any difference and it if does, it signifies that you have a problem elsewhere, but there is no harm in trying...?

cheers
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janusz200
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Re: Need help. Engine Ground Straps

Post by janusz200 »

In my car (1980 M90 without Mortronic) unconnected ground braided flat wire between splash wall and head cover caused the malfunction of temperature and gasoline level gauges. I didn’t noticed influence on idle. But idle in my car was much better after tightening small curved vent hose between throttle housing and head cover - see photo. It’s mounted under the throttle so the acces to check and improve is pretty bad. Leaking air is a false air cousing unsmooth work on idle.

By the way - my engine never worked smooth on idle. I checked a lot of things on air supply and electric side and it helped nothing.
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1980 635 CSi EU
M90/L-Jetronic/manual
Ronnie Wilson
Posts: 239
Joined: Fri Nov 18, 2016 11:40 pm
Location: Liverpool uk

Re: Need help. Engine Ground Straps

Post by Ronnie Wilson »

Thanks Guys.

I’v Got my Fingers crossed 🤞 it’s those Earth Straps Missing that’s causing the lumpy ible.
The last owner in 2000 had the Head Gasket replaced after it failed around number 6 Cylinder and then had the Cylinder Head skimmed.
Just hopping the Mechanic forgot to re-fit them after re-building the Cylinder Head. If only everything was that easy.

Thanks
Ronnie
Liverpool uk.
1986 635csi.
Bronze Beige Metallic.
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