I shall let the picture above speak for itself. The one on the left was a rescued ECU, the one on the right is removed from my XJR6 (Rose), the latter has been running just a few months.

Those who have read about the recovery of my XJR6 (Rose) knew why Rose died in the first place a few years ago. A badly corroded ECU was the main cause, but the immobilizer was the first cause; left in the open was next; then water in the tank; water in fuel rail...... All fixed and a new ECU saved Rose from the grave. Then after a few months of happy usage, Rose cranked but habitually refused to start after a long journey, and eventually died again, with no crank at all. The cause of all these was, surprisingly, a corroded ECU, with pins badly oxidized and a few fallen off (possibly when unplugging - indicating how fragile the pins were when there is corrosion). Rose does not have sunroof, but a little hole was found between the firewall where the it meets the beam of the bonnet. This was sealed off, and I also sealed the natural crack at the base of the front windscreen to ensure water is diverted to the sides. The mechanic also fixed the air duct behind the glove box as I had a theory that condensation behind the deck was the cause of a badly corroded radio and surface rust on the airbag control box. Then another new ECU from Andy gave Rose a third life. All was well until a few days ago when Rose started stalling suddenly at the traffic lights. DTC scan suggested a bad purge valve - sounds reasonable, as Rose often has problems refueling at the gas station. Tank pressure typically rejected the gun many times before successfully filling the tank up. So was wondering how this may affect the fuel supply to the front... However, when Rose is in motion she functions well and never disappoints.

So yesterday, my mechanic brought me back the corroded ECU, saying that he found a guy who is willing to try and remove the two ECU corroded receivers and re-soldier new ones. We tried to install this recovered ECU on Rose and she started right up, and drives even better. That is such good news! However, what the mechanic and I found was when we removed the on-car ECU to replace it with the rescued ECU, the on-car ECU showed corrosion on a few spots. See picture above.

This could be the real cause of recent stalling at the traffic lights. Now that we have ruled out water sippage, and condensation behind the deck (mostly from the left side), the question is where did the moisture come from? I just wonder if the ECU gets warm during driving and then cools down after use and the humidity in Hong Kong is causing moisture to gather round the connectors and causes such damage within such a short time.

My question is can we and how best to waterpoof the ECU? Was wondering what rally cars and aviation aircraft do to prevent important components from getting wet or moist.

 

There is a special grease that can be applied to electrical connectors that does not conduct electricity. I don't know if this will help, but if you are sure that you have sealed off all external water leads, it might be worth a try.

 

I think that 'special grease' is Silicon grease. I, along with many other motorcyclists, use it on all electrical connections on the bike to stop moisture getting to them.
You might also want to try another product that is popular with bikers - see here:
ACF-50 and Corrosion Block total Corrosion Control

 

Found water ingress!

I have been parking my XJR outdoor for almost a year now since I moved house, and I either parked her on a level spot near the house, or on the hillside with the nose heading down. A forum member recently said his car stalled more with the nose heading down, so the idea of parking direction may give rise to different observation in diagnosing problem immediately came to mind. So it has been raining with occasional downpours for a few days. Rose regained her past ECU yesterday, and was more responsive than the one that has started developing corrosion. I parked Rose with her nose pointing upwards. The next day afternoon it was raining again. Rose started first crank. While I tidied up the interior, Rose stalled. Tried to restart; cranked but no start. As the mechanic did not put the interior cover back on, pending findings of waterproof products, I could reach and see the ECU on the right side of the footwell. I took a look and saw water dripping from above the gas pedal. Took a closer look and alas! the rim of the ECU connectors was all wet, water kept dripping from above. This leak obviously came from the unseen part under the windscreen. Phoned the mechanic for advice: then unplugged the car battery, removed and inverted the ECU to drain water therein..... Oh dear, must track down on the source of the leak or else there is no end to this ECU saga.

 

You can use another ECU and just transfer the original PROMs to your replacement unit. (unless the PROMs are damaged)

This TSB/Service Action should give you info on how the PROMs are replaced. I performed this dozens of time during the RECALL almost 20 years ago.

I just used a broad/flat screwdriver to carefully remove the PROMs. It's not difficult.

bob

 

A couple thoughts:

1) Take care using dielectric grease to seal these connections unless one can guarantee the grease will not get onto the conductors/pins. Dielectric grease is non-conductive, an insulator, and if one were to get the grease on the conductors/pins, that will cause more trouble than solve. Dielectric grease is good for lubricating plastic seals and sometimes increasing waterproofing. But the grease can migrate and cause issues too, so again take care. A good alternative might be conductive grease such as NO-OX-ID.

https://www.sanchem.com/electrical-c...lubricant.html

https://www.sanchem.com/docs/NO-OX-I...al%20Grade.pdf

2) I've been giving some thought to dealing with the secondary cause of this issue, water following the wiring down into the connectors and ECU. The primary cause of course is water leaking into the interior wiring of the car somehow, which should always be addressed. But if we can keep any leaking water from following the wiring into the ECU, that would at least avoid ECU damage. The main issue is that the ECU connectors face up, so I was thinking that if we flipped the ECU so that the connectors were facing down, or at worst sideways, then the water could not follow the wiring into the connectors and ECU itself.

I haven't looked to see if the ECU could be moved up into the dash, perhaps behind or beside the glove box, and the ECU wiring re-routed. If so, that would be the easiest option. I plan to look into that later.

Another less ideal option would be to build an extension harness to plug into the factory harness and bridge to wherever the ECU gets moved.

.

 

I was thinking heading that direction too, i.e. relocate the ECU, but even if there is an extension harness, we must first waterproof the primary connectors before connecting to an extension harness. However, if we can achieve the first defence, there is not much point moving the ECU....?

 

Actually in either option 1 or 2, you don't have to waterproof the primary connectors... that's the beauty of it. And I don't think you'd ever completely waterproof those connectors. They just aren't built for it. If one had a continuous leak, the water would eventually win.

But moving the ECU to higher point, or maybe flipping it over would solve the issue without worrying about waterproofing the connection.... by keeping the water from ever reaching the connectors in the first place

Water follows gravity down the wires, into the connectors, into the ECU in the current configuration. If you rotate the ECU or move the ECU such that the connectors are now above the lowest part/loop of the wiring harness, water can't fall "up" into the connectors and ECU. If you have a water leak, water may still run down the wires (which also really needs to get fixed), but the water will now flow and fall to the lowest part of the wiring harness and drip off, not run up into the connectors and ECU.

.

 

Flip it ,

 

I agree. Would like to, but have to make sure there is enough slack to be found in the harness to flip the ECU over. Otherwise the ECU will have to be relocated. Haven't investigated yet though.

I've been busy rebuilding the M62 supercharger for my son's 1995 Buick Riviera in the evening after work. He's going back to school soon, so we need to get the intake back together ASAP.

Once that's done, I'll get back to the XJR.
.

 

See what damage water can cause to the ECU connectors.

 

Thinking in terms of flipping the ECU so the connectors are upside down would be hard to to physically remount along with the proper " case " grounding paths so a extension of the wire bundles with a lower dripping point is in my head .

My sockets where replaced in it's past and have turned black for what ever reason and they left the individual wire seals off . Some sort of Tech school class project car best I can figure .

 

To clean them, see this:
https://www.instructables.com/id/How...es-in-minutes/

I've done it on motorbikes and it works great

 

[QUOTE=al_roethlisberger;1929975]A couple thoughts:

1) Take care using dielectric grease to seal these connections unless one can guarantee the grease will not get onto the conductors/pins. Dielectric grease is non-conductive, an insulator, and if one were to get the grease on the conductors/pins, that will cause more trouble than solve. Dielectric grease is good for lubricating plastic seals and sometimes increasing waterproofing. But the grease can migrate and cause issues too, so again take care. A good alternative might be conductive grease such as NO-OX-ID.

Al, if you use conductive grease you have the risk of providing a conduction path between pins; hence the reason for using Dialectric...

 

It rained for almost a week so I couldn't do anything except trying to use packing film to temporarily seal the louver under the windscreen with the aim of diverting water away. However, it is now proven that it did not help at all. With the nose pointing upward, water still found way entering the cabin and flew to the floor. I inspected Rose carefully and was shocked to find that the floor pan at the footwell of the back seat was heavily soaked with water flowing from the front. Could not see the water but I was surprise how much water the factory carpet can soak up. I used a huge bathing towel to dry the pan and only after at least 15 times squeeze-to-dry the towel stop dripping with water. There must a huge hole somewhere that has been allowing such volume water filling up the floor pan.

Meanwhile, I have bought both the ACF-50 and NO-OX-ID products and am still waiting the arrival of ACF-50. However, prior to that I have experimented the clean-and-neutralize method suggested by Sheff928. I reconnected the ECU after drying out the pins and connectors and Rose started right up. Once the ACF-50 arrives I shall try to apply it to the metal pins and female connectors, and seal the outside of the connectors with NO-OX-ID to block out water and moisture.

 

I found a gap in the seam where the side fender panel sheet metal overlaps the sheet panel across the top of the engine firewall . I just put some silicone bathtub sealer on it .

 

There is a sunroof drain tube (rubber) that comes down inside the A post and connects to a metal tube that then exits the chassis through the inner wing.

I would check that the rubber tube is not perished or has become disconnected. Pictures show the LH side but from memory the RH side is the same.

 

There is a rubber boot that covers the wiring where it goes through the body. With age that can leak and the water follows the wires right into the ECU.

 

Rose does not have a sun roof but I suspect that something similar must be diverting water but leaking mid-way, or some channels blocked and leaked when overflowing. I think I can try pouring coloured water on the windscreen to reproduce the leak and then track down the pathways.

 

Air conditioner plenum other then the normal condensation drain ?