Fixed the most bizarre electrical problem today ....

[60six]

Friend has a Land Rover 110 Defender, and it had been misfiring for no apparent reason, plus the OBD2 port gave up.

Whilst removing the ECU the plug was FULL of oil - I assumed the driver must of spilt some but the oil was only in the plug.

Apparently, this oil is diesel from the injectors, that travels along the loom, into the cabin, through various ducts, up and around various obsticles and stops when it reaches the plug, then if left long enough, kills the ecu!

Cleaned it out and reassembling fixed issue straight away.

It just does not seem feesible but this actually happens - it defies gravity, grommets, loom tape, everything!

Are there any other bizarre car issues which just seem impossible?

[colnerov]

Jan 12, 2019 22:38:26 GMT 60six said:

Friend has a Land Rover 110 Defender, and it had been misfiring for no apparent reason, plus the OBD2 port gave up.

Whilst removing the ECU the plug was FULL of oil - I assumed the driver must of spilt some but the oil was only in the plug.

Apparently, this oil is diesel from the injectors, that travels along the loom, into the cabin, through various ducts, up and around various obsticles and stops when it reaches the plug, then if left long enough, kills the ecu!

Cleaned it out and reassembling fixed issue straight away.

It just does not seem feesible but this actually happens - it defies gravity, grommets, loom tape, everything!

Are there any other bizarre car issues which just seem impossible?

Hi, Yes can be a problem with TD5 engines because of the high pressures involved and the direct connection between engine internals and the ECU.

Colin

[Waxoyling Lyrical]

Jan 12, 2019 22:38:26 GMT 60six said:

Are there any other bizarre car issues which just seem impossible?

There probably will be, with some modern car wiring looms (including Mercedes) made out of self-degrading plastic! BMW E30s had a common fault with the wiring loom to door connectors becoming corroded because of a bad bit of design that created an unnecessarily long current loop, leading to central locking faults.

What I don't fully understand is why oil should affect the electrics in any significant way while contained within a connector, since it doesn't conduct electricity (at least, not as much as water) nor cause corrosion.

[colnerov]

Jan 12, 2019 23:39:35 GMT Waxoyling Lyrical said:

What I don't fully understand is why oil should affect the electrics in any significant way while contained within a connector, since it doesn't conduct electricity (at least, not as much as water) nor cause corrosion.

Hi, Because oil does conduct electricity with varying degrees of resistance and ECUs rely on small changes in resistance from various sensors to change parameters in the fuelling map. Plus hot oil can be quite acidic.

Colin

[ahebron]

Tail lights that let water in and then get to a depth where the bulb is immersed.
Water then tracks down the cables eventually getting to parts it shouldnt and effectively writing the car off.
Yes it gets across connectors in the loom.
VW Amaroks are a good example and yes I am keeping an eye on mine, drain holes drilled already.

Adrian

[Sammo]

We get it at work with the Corsa C. The seal inside the oil pressure switch gives up and the engine pumps oil through the entire loom and eventually into the ECU. The first the customer knows about it is when the car eventually goes into limp mode because the ECU has begun to fry itself!

[braaap]

Probably a problem (= proplembly? ) with other cars, too but I know that a wet plug socket for a tow bar sometimes causes electrical problemes (aren´t they called gremlins in english?) with the instrument panel of vw t4 busses.

[welshpug]

very common issue with the TD5's, psa had a similar thing to the corsa with the coolant sensor on certain engines/cars due to the same direct wire run from sensor to ecu.

[tommytwo4g]

"Because oil does conduct electricity with varying degrees of resistance and ECUs rely on small changes in resistance from various sensors to change parameters in the fuelling map. Plus hot oil can be quite acidic".

Spot on, that man. I have seen "blue electricity" tracking along an oily wire on a Moog automatic milling machine. Once the wire was cleaned, the problem went away.

My Rover 820 had dirty oily wiring and that was causing the engine to idle at 3000 revs when hot. Cleaned up the the engine compartment wiring and no problem since.

[rattlecan]

Jan 12, 2019 22:38:26 GMT 60six said:

Friend has a Land Rover 110 Defender, and it had been misfiring for no apparent reason, plus the OBD2 port gave up.

Whilst removing the ECU the plug was FULL of oil - I assumed the driver must of spilt some but the oil was only in the plug.

Apparently, this oil is diesel from the injectors, that travels along the loom, into the cabin, through various ducts, up and around various obsticles and stops when it reaches the plug, then if left long enough, kills the ecu!

Cleaned it out and reassembling fixed issue straight away.

It just does not seem feesible but this actually happens - it defies gravity, grommets, loom tape, everything!

Are there any other bizarre car issues which just seem impossible?

This is a common issue on Cat truck engines

[pavpav]

Common on Mercedes R172s

[Ryannn]

My CLK daily does the same thing, leaks oil from the cam sensors into the engine loom. Cannot be fixed once it’s started and naks up the fuelling.

I’ve spent the last few months changing various sensors but it seems ever more likely that the loom is borked.

[luckyseven]

I had a Hahhhnda VFR hack when I was dispatch riding. The seat chafed through the paint on the subframe rails, and I just wrapped it in gaffer tape as a quick rust preventative measure. Of course, it rusted anyway, the seat chafed through the gaffer and little tendrils of rust-impregnated tape gradually unravelled and worked their way downwards using the magic of gravity.

Then, in a corner, they earthed the battery across the frame rails Fortunately, this happened at night so the bright actinic flash gave me a hint as to why the bike had suddenly cut out mid-corner


This was not totally reassuring though, especially not as it took place in a triangle of space-time defined by the seat, the petrol tank and my nuts

[Ritchie]

I had a similar thing on a Suzuki zr50 when I was a boy. The tank was bare and rusty, which then chafed through the coil lead on the frame top tube.The sparks jumping from the sides of the tank to my knees on a wet day were a bit of a surprise!