Another Tamd22 Earthing Thread.. Isolated Return. 55Amp Fuse.Help Needed

J

jw_2000_uk

Well-Known Member
Joined
28 Jan 2013
Messages
103
Visit site
Hi lads.. Followed wiring diagram.

But my block has permanent ground to it.. If i put a multi-meter + to battery +. then neg to a bolt on the engine, it shows 12.6V at all times. i take it this is not correct?

even when i disconnect all Neg terminals off the starter, it still shows 12.6:confused::confused::confused::confused:

ive got more testing to do.. but any idea why this is happening lads?

also, on the chance that the 55amp fuse has gone (will be testing), could i replace with one of these
http://www.ebay.co.uk/itm/Fuse-Span...732633?hash=item1a1bdebfd9:g:3qYAAOSwmfhX2ago

I have heard control cables can ground a engine??

I unplugged all my accessories, still the block was grounded, leaving just the positive form battery selector switch
 

Attachments

  • 2014-09-11 004.jpg
    2014-09-11 004.jpg
    91.3 KB · Views: 1
  • 2014-09-11 008.jpg
    2014-09-11 008.jpg
    95.5 KB · Views: 1
  • 2014-09-12 008.jpg
    2014-09-12 008.jpg
    97.7 KB · Views: 1
  • 2014-09-12 009.jpg
    2014-09-12 009.jpg
    93.6 KB · Views: 1
Last edited:
There are many possible routes for ground to engine. Could be via engine sensors and the dash panel or other components in the system such as anodes bonded to the engine via earth wires.
 
I did disconnect all sensors to check

oil,temp,warning,shut off solenoid,egt thermo,

theres no anodes via earth wires.


The dash connects via a multi plug, nothing has been changed there..

Strange
 
nigelmercier said:
Try removing the 55A fuse, the start/stop relay may be stuck.
Click to expand...

Tried that also... no change. I can take the fuse out, and stop solenoid and glow plugs still work.

Thing is, everything works perfectly.

I just noticed this the other day. And realised it shouldnt be grounded, other then start, stop, glow plugs.
 
I recognise that battery picture it looks like its from a OCQUETEAU 625. I had the same engine and my main earth cable from the battery connected to one of the gear box bolts to the engine.
 
jamie langstone said:
I recognise that battery picture it looks like its from a OCQUETEAU 625. I had the same engine and my main earth cable from the battery connected to one of the gear box bolts to the engine.
Click to expand...

Spot on mate. Thats the boat.

Ok, i'll change that bit. So under a *Nut for the gearbox. As it slots on threads then tightened with nuts.

Where the flywheel cover is bolted.

So definitely the gearbox bud?
 
right, ive now disconnected every extra. leaving just the volvo stuff.

gone to single battery.

- battery to - post on starter

+ battery to + solenoid.

red mulitmeter lead on battery +
then black on a engine bolt i get 0V. perfect.

BUT as soon as i put either the negative from the alternator
or from the sensors,on the the starter - (witch is where they should go)
then i get 9v on the engine block at all times.

55amp fuse still makes no difference if connected or not.

could it be the relay in the picture?

as i said, the engine runs fine, starts and stops fine. i just don't want to speed up corrosion down the shaft to my prop.
 

Attachments

  • 20161115_150444_resized.jpg
    20161115_150444_resized.jpg
    94.7 KB · Views: 0
  • 20161115_161529_resized.jpg
    20161115_161529_resized.jpg
    92.6 KB · Views: 0
Last edited:
I am not understanding why you think there is a problem.
If you put the multimeter between the pos and neg posts of the battery you get battery voltage...at all times.
Since the neg post is connected permanently to the engine block, you will always get battery voltage between the block and the pos battery post.
 
dpb said:
I am not understanding why you think there is a problem.
If you put the multimeter between the pos and neg posts of the battery you get battery voltage...at all times.
Since the neg post is connected permanently to the engine block, you will always get battery voltage between the block and the pos battery post.
Click to expand...

On a normal engine yes. But im sure this being isolated earth. It shouldn't be the case?

Its driving me mad lol.
 
nigelmercier said:
On my starter solenoid there is an insulator to prevent the low current negative from touching the body, it had got crushed.
Click to expand...

Will check this, although its a brand new starter. And all looks fine :(

Can i just confirm nigel, that there is a issue with my earth, and im not worrying for nothing?
 
jw_2000_uk said:
On a normal engine yes. But im sure this being isolated earth. It shouldn't be the case?
Click to expand...

sorry I cannot follow this. What is isolated earth? Is it a term for an marine engine installation form?
I could understand what it implies, fail to see the point though (other than possibly fizzing)

cheers

V.
 
vas said:
sorry I cannot follow this. What is isolated earth? Is it a term for an marine engine installation form?
I could understand what it implies, fail to see the point though (other than possibly fizzing)

cheers

V.
Click to expand...

It is mate.. heres a little more info.

The engine block and saildrive are isolated from battery negative ('earth' or ground) when the engine is not running i.e. most of the time. There is a relay (identified by a 5 in the wiring diagram in the Owners Manual) that connects the negative to the block, through the fuse link you mention (numbered 6), when the 'ignition' is turned on. It allows the glow plugs and stop solenoid to work as they have a ground return rather than a separate wire.

The starter, like the alternator, should be insulated return, and therefore have no effect on the fuse you mention. If yours is not insulated return then the starter would certainly blow the fuse.
 
The lower relay is energised from the glow plug circuit and the engine stop circuit in order to provide a negative path from the engine block during these two operations.

However what I think you have missed is that the glow plug circuit remains energised via the "ignition" switch during the starting phase .

The result is that the lower relay is energised during preheating and during cranking, connecting the engine block to battery negative via the fuse. That is what you observe.

If the starter motor is of the insulated negative type there should be no path from it to the engine block. The negative return should be directly back to the battery negative via the negative isolating switch.
 
nigelmercier said:
Is the new starter an isolated type?

If you have the 55A fuse and start/stop relay, the engine should be isolated.
Click to expand...

I was told it was mate. It has a lead from starter earth to a spade next to positive

Its this one. Look at this on eBay http://www.ebay.co.uk/itm/252352199746

Yep 100% mine is a isolated earth engine.

Way back the 55amp went.. so stop solenoid wouldnt work.

Replaced it, fixed the problem.

Now it makes no difference if i connect the fuse or not.
 
Last edited:
You must log in or register to reply here.

Share this page

Top