Is there only 1 correct place to put 3 engine earth leads ?
Discussion
Following on from my previous threads (my 350 not running after new clutch etc.) I have noticed that the 3 earth leads (from the wiring loom ?) have been put back in a completely different position to my other wedge, my 390 ?
The 390 earth leads are here :-
The 350 earth's have been put back here :-
Does it make a difference ?
Many Thanks
Regards
Ian
The 390 earth leads are here :-
The 350 earth's have been put back here :-
Does it make a difference ?
Many Thanks
Regards
Ian
Wedg1e said:
Not as long as ALL mating surfaces are free of corrosion and the wires themselves aren't corroded. Be worth checking for good continuity between engine and battery negative post too.
Sorry Wedg1e, I don't know how to do that ???I really wish you live nearer, having 2 kn*ckered wedges is driving me nuts
Can anybody please come and fix my wedge, or at least diagnose the problem, I will of course pay for your services, I try these things that you kind members suggest but I don't really know what I'm doing
in all honesty.Regards
Ian
What's up with the 390?
The ECU will only see a decent earth return to the battery if the battery itself has a good hard connection to the block (since that's where the ECU earths are fastened).
So first off you need the ring terminals on the end of the ECU earth wires to be as sparkly clean as a sparkly clean thing (emery, wet'n'dry, fibreglass pencil, Brillo pad, wife's nail board are all good).
Also clean the surface of the cylinder head where the rings make contact, both sides of any washers, the underside of the bolt head and the thread on both bolt and its hole need to be free from corrosion (or grease, since it can act as an insulator). Reassemble and make sure bolt is tight, then smear with Vaseline (or silicon grease, better still) to keep the moisture away.
Now find the earth strap that ties the battery to the block (or it may go to the chassis, with another to the block). Remove it and clean the ends and the contact areas in the same way.
In theory that's it, but the earth straps themselves can go high-resistance so the first thing to do is stick your meter on resistance, disconnect the battery (+) lead and measure from the battery (-) to the block, you want to see 0.000 Ohms or as near as dammit, and no, 1 Ohm is not as near as dammit. This is where a digital meter scores over a moving-coil type (although some moving-coils have a high-current output which... but I'm digressing).
Even this may not be conclusive: what you can then do (reconnect the battery (+) first) is put your meter on volts DC and measure from the battery (-) to the block. Eh? you say, what will that do? Well, when you crank the engine, if the earth strap is high resistance you will see a voltage develop across it: it needs to be sweet-F.A. OK, I'll allow you half a volt. Any more than that and you could do with a new earth strap.
Now a high-resistance earth strap in itself won't (necessarily) kill the injection system but as almost all the electrical loads of the car go through that strap you want it to present as little resistance to current flow as possible, so your lights will be brighter, the starter will spin faster and the stereo will go louder
- so it's worth doing periodically anyway.
By the time your car is running again you'll know more than you think you needed to
ETA: although I'm off darn sarf I'll be passing a good way to the west of London so not really in a position to stop by unfortunately; if this changes I'll let you know.
You're still wlecome to post your ECU up and I'll check it out and get it back to you ASAP.
The ECU will only see a decent earth return to the battery if the battery itself has a good hard connection to the block (since that's where the ECU earths are fastened).
So first off you need the ring terminals on the end of the ECU earth wires to be as sparkly clean as a sparkly clean thing (emery, wet'n'dry, fibreglass pencil, Brillo pad, wife's nail board are all good).
Also clean the surface of the cylinder head where the rings make contact, both sides of any washers, the underside of the bolt head and the thread on both bolt and its hole need to be free from corrosion (or grease, since it can act as an insulator). Reassemble and make sure bolt is tight, then smear with Vaseline (or silicon grease, better still) to keep the moisture away.
Now find the earth strap that ties the battery to the block (or it may go to the chassis, with another to the block). Remove it and clean the ends and the contact areas in the same way.
In theory that's it, but the earth straps themselves can go high-resistance so the first thing to do is stick your meter on resistance, disconnect the battery (+) lead and measure from the battery (-) to the block, you want to see 0.000 Ohms or as near as dammit, and no, 1 Ohm is not as near as dammit. This is where a digital meter scores over a moving-coil type (although some moving-coils have a high-current output which... but I'm digressing).
Even this may not be conclusive: what you can then do (reconnect the battery (+) first) is put your meter on volts DC and measure from the battery (-) to the block. Eh? you say, what will that do? Well, when you crank the engine, if the earth strap is high resistance you will see a voltage develop across it: it needs to be sweet-F.A. OK, I'll allow you half a volt. Any more than that and you could do with a new earth strap.
Now a high-resistance earth strap in itself won't (necessarily) kill the injection system but as almost all the electrical loads of the car go through that strap you want it to present as little resistance to current flow as possible, so your lights will be brighter, the starter will spin faster and the stereo will go louder
- so it's worth doing periodically anyway.By the time your car is running again you'll know more than you think you needed to
ETA: although I'm off darn sarf I'll be passing a good way to the west of London so not really in a position to stop by unfortunately; if this changes I'll let you know.
You're still wlecome to post your ECU up and I'll check it out and get it back to you ASAP.
Wedg1e said:
What's up with the 390?
It needs all the MOT work doing to it still 
, th ewelding of the chassis, brakes, electrical gremlins. I am itching for it to be repaired but as my 350i is a non runner and trying to get the fixed first.Can't wait for the 390 to be finished, it goes like the clappers and sounds awesome
My mechanic is taking on the works but although good is quite slow
Thanks's for your long post about the earths etc., will hopefully have a good clean up the weekend (if the wife allows me to ???)
maston said:
Wedg1e said:
Not as long as ALL mating surfaces are free of corrosion and the wires themselves aren't corroded. Be worth checking for good continuity between engine and battery negative post too.
Sorry Wedg1e, I don't know how to do that ???Ian
We will teach you how to do continuity tests first..which is all you need so far. Not to worry, the lesson will take 10-20 seconds.
+8
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