Endless electrical failures
11-11-2022, 11:40 AM
#16
Rennlist Member
I don't have anything specific and have no experience since I'm still hunting for the right Cayenne but from other older vehicles I've owned over many years I would say:
Since it happens seemingly at random I would suspect something electrically loose that is okay at times or perhaps something is drawing current when it should not. Perhaps pull a fuse one at a time on something not crucial to vehicle operation and see if it narrows things down. Maybe, after checking those splices, check those wires in the door and connections under the seat or near anything that gets moved around.
Did you check the alternator output to make sure it is putting out the correct voltage?
For someone else: Do the Cayennes suffer from poor chassis ground like some other vehicles?
Sounds like a very frustrating issue for sure.
Since it happens seemingly at random I would suspect something electrically loose that is okay at times or perhaps something is drawing current when it should not. Perhaps pull a fuse one at a time on something not crucial to vehicle operation and see if it narrows things down. Maybe, after checking those splices, check those wires in the door and connections under the seat or near anything that gets moved around.
Did you check the alternator output to make sure it is putting out the correct voltage?
For someone else: Do the Cayennes suffer from poor chassis ground like some other vehicles?
Sounds like a very frustrating issue for sure.
11-11-2022, 12:12 PM
#17
Drifting
Thanks Rick, I don't hear a hissing and my battery seems to be fine. Last Saturday I opened up the wiring harness and only found one splice. Cut it and respliced. Harness looked to be in good shape unlike W124 engine harnesses with biodegradable sheathing where you can easily see bare copper where the sheath has cracked and fallen off. a few pics.
The start issue seems to be extremely random. For 2 days it would start on the second turn of the key every time. Then it took 5 times once. Then it started on the first time twice in a row. SO much joy in those 2 moments. Now it's back to 1-2-3 turns.
I think I'm going to get a new door controller and new wiring harness though I may get the new relay at the battery first.
One interesting data point is that if the truck is running. You turn it off, it will always, 100% of the time, start back up again instantly. But there's no rhyme or reason if you wait a few minutes.
Truck has been off the tender or charger since Saturday or maybe even Friday.
The start issue seems to be extremely random. For 2 days it would start on the second turn of the key every time. Then it took 5 times once. Then it started on the first time twice in a row. SO much joy in those 2 moments. Now it's back to 1-2-3 turns.
I think I'm going to get a new door controller and new wiring harness though I may get the new relay at the battery first.
One interesting data point is that if the truck is running. You turn it off, it will always, 100% of the time, start back up again instantly. But there's no rhyme or reason if you wait a few minutes.
Truck has been off the tender or charger since Saturday or maybe even Friday.
I'm surprised you found one one splice. My truck had four, one being a really heavy black wire 3-way and three being smaller wires.
Before I swapped the engine the truck started flawlessly every time, even though it was running on 7 cylinders because of a burned valve.
When I swapped in the used engine, I did not swap the starter over as the used engine came with a starter installed. Now the first start attempt is either really weak or a non-start. The battery voltage is good; I checked. Once it's running it will restart first try every time.
I suspect the starter that was supplied with the used engine is on the way out. I am going to put the known-good starter off the bad engine into the truck next weekend and see if that improves things.
There are quite a few ground points that you might check. Off memory, the main engine ground is in front of the right front wheel on the bottom of he frame rail. There's a ground point in the cowl, right side, next to the ECU. There's a ground point on the left frame rail outboard side, forward end, next to the A/C pipework. Probably more that I can't recall.