Just re-wired mine on my 4x4 saff using new relay and wire rated at 30amp. All
connectors used are rated at 30 amp as well. It's got a new 30amp fused 12v feed direct from battery and new relay earth from battery. Pump has a new earth to the inside of rear wing. I had to re-use the pump connectors as these are no longer available so just soldered new wire into last 3 inches of existing wire before the pump.

Voltage at battery on idle is 13.8v, at relay it's 13.3v and at pump it's 13.1 volts.

So I'm losing 0.7 volts now between battery and pump. Is that about right?

Cheers.

 

i would run the earth direct to the battery as doin it to the body you are using 2 plus year old metal as an earth so could be causing resistance

 

The relay is earthed to battery but the pump earth is to a panel in the boot. Seems to be working okay at the moment. I guess I could splice the earth wire into the relay earth going back to the battery for added security.

 

got to be wrth a try eh mate, have you tested the voltage whilst under load also as this is when it counts

 

As long as it's over 12v that's all that matters. It's a 12 v pump so at 12v it's at full power. You only need to be concerned if it's running below 12v

 

That's great. Cheers.

 

Hi Jim,
Its relatively pointless testing the pump at idle, it needs testing at full boost mate. Ensure its well above 12v at 5000rpm with full boost held in 3rd gear or above. Once done, flick the cars lights on and run her again.

 

I wouldn't cut into the relay earth direct from the battery, unless you know for a fact that it can carry the amount of current the pump can draw, this is 18amps at full lockout load and 12v, so obviously less amps at higher voltage.
I would run a seperate earth DIRECT to the battery, the whole point of the rewire is to lose high resistances, ANY joint will give you a resistance, so the less the better, unless you use super cooled super conductors for the wiring!!
A loss of 0.7V over that length is ok, you could cut this down if you wanted using different wire but seriously costly for some.
tabetha

 

Cheers chaps. I'll rig up a voltmeter in the car and test it under load as suggested by Stu. I'll post up the results.

 

Update: disaster! I took it out for a spin with a mate in the passenger checking the voltage throughout. All was good - was holding over 13 volts. Gradually uped thr revs to 6k and all was fine. Then did a run with lights on to about 6k and voltage was 13+ volts all the way. Backed off and by tim I'd dropped down to 30mph it felt like running on 3 cylinders. I gently drove the couple of hundred yards back to my road watching the oil pressure which was fine but as I turned into my road it dropped to 10psi then nothing really quickly. I turned off immediately and towed it back to my house.

I'm guess I've melted a piston/s. I'm gutted as the re-wire voltage was good all the way but something must have gone wrong unless it's just co-incidence but seems unlikely.

It's only a motor at the end of the day so not too upset and I've always fancied re-building an engine

Can't see any damage be removing the plugs but I guess it must be piston as no visible oil loss.

Edited to say there was no smoke from exhaust and oil level in sump hasn't dropped at all. All plugs look intact.

 

Not good matey, hopefully its an easy (and cheap) fix!

 

If the engine was turning, a holed piston would make no difference to the pressure.
First thing I'd do is take filter(and extension) off, plugs out turn over to see if oil comes up the supply hole in the bottom area of the filter housing on block, hoping it's something simple like a knackered oil filter.
Could also do a comp test at same time if you want.
tabetha