Starting Issues 2008 XC90

[jimmy57]

If you use a voltmeter to check voltage drop you can find THE cable or the one crimped lug on one end of the one cable that is causing the problem. The chance of it being the cable itself is very low. The + cable from rear runs inside the car and is protected in areas where it is underfoot. The greater vulnerability is cable being crushed by 2nd row seat but that would be a short to ground that would fry the battery. If you pierce the insulation on the + cable behind the fusebox and the other voltmeter lead on the stud in back of the fusebox where cables join and then probe stud to post on starter where that cable connects, you will likely find that one of those tests shows 2 volts indicating a big loss to some faulty connection. The fact you have a replaced starter means the vehicle had a bad starter (these starters have some history of bushings failing and internal armature drag with 250 A draw while it tries to turn engine) and it may have overheated one of those crimped lugs and it now is a resistive connection from the oxidized copper wire. These connections can usually be fixed using a mini torch and rosin core solder to solder that wire to the lug terminal. Follow that with heat shrink tape to cover that last couple of inches of cable insulation where the soldering requires it be removed to prevent it burning.

[Roger_850T]

I've never tried the positive only, but have gotten it to start running the ground only. But it still doesn't turn over full speed. Problem with a ground issue is that could be anywhere right? Not just on the cable from battery to front. so then the trick becomes finding it.

This is important - I had been presuming the positive cable, but this suggests the ground.

I would need to check, but I know sometimes the ground between the engine block and the body can corrode and get high resistance - that would explain your symptoms.

When you did your cranking tests (measuring at the post in the engine bay) - what did you use for a ground? Was it on the body or on the engine?

Roger

[RickHaleParker]

This is important - I had been presuming the positive cable, but this suggests the ground.

I'm still leaning towards the positive cable because when he did the one wire self jump start on the ground side, it cranked but not very well. With a bad positive cable, doing a ground side jump would lower the over all resistance of the closed circuit loop, possibly enough to barley get it started.

I'm hoping he will do the one wire jump on the positive side because the test results would be pretty conclusive.

[stljrdnfan]

Hey folks, thanks for all the input. I haven't been able to work on this for awhile now. But I plan on using the cable I made my jumper cables out of to make a replacement positive cable (the wire is free) and just run it around the outside of the car and see if that changes anything. If it does I'll just find a way to run it thought the vehicle and replace it permanently.