I think you are on the right track. The Brown/White wire is fed from fuse #3 in the left side engine bay box, which is fed through your rusty terminal. That wire when clicked closed with the White wire sends current to the starter solenoid.

You may have noticed that the center-right bulkhead terminal feeds the starter directly from the battery, once the solenoid contacts close.

For testing purposes, you can jump the Brown/White wire socket terminal with the White one (the larger wires), using a similar gauge jumper wire. The starter (and engine) should crank. Do this with the key off, so the engine won't start. This is an easy way to repeatedly test the solenoid and starter. There will be a little spark at the terminal as you engage.

 

OK, I’ve done a few more tests and still no luck, keen to get some ideas.

1) I swapped relays, still no crank.
2) I bridged pins 3 & 5, and other than a spark, nothing happened, not even an audible clunk from the solenoid.
3) I put my multimeter between pins 3 & 5 (pretty sure that’s a good way to ruin a multimeter) it read 12V, no crank.
4) Used the multimeter to measure the voltage between the bulkhead starter connector, and ground when the key was turned, and it was a constant 12V (consistent with not hearing a clunk).
5) I tried measuring the voltage on the starter when the key was turned, but I wasn’t sure what I was supposed to be measuring, so registered nothing on the multimeter.
6) I inspected the engine ground connector, it seemed fine.
7) I tried to inspect the starter ground, but couldn’t figure out where the wire went, I lost it somewhere over the alternator.

My next plan is to try and figure how to measure if the solenoid is getting 12V, but I’m not sure where to measure. It would be a lot easier if the exhaust wasn’t in the way.

Any ideas?

 

Mr. Bath,

Please confirm that you have cleaned the rusty terminal on the bulkhead! You could read 12V all day but when it comes time for some real current to flow then it won't be able to get through the rust and dirt.

With that terminal and the others all clean and tight (to include the solenoid connections), and fuse #3 intact, the jumper method WILL engage the starter or at least the solenoid. If nothing happens then there is a 95% chance that the starter solenoid has failed. The starter motor itself could be duff but much more likely to be the solenoid. Either way, it is a starter out/replacement job.

 

Thanks, yes, I did clean up the bulkhead terminal. I actually think that the problem is getting worse (more frequent).

I will check fuse #3.

I will also have a really thorough look at the connections to the solenoid, as I’ve got a better idea of what they should look like now.

Then I’ll try to energise it (the solenoid) with 12V directly as an additional check.

Not looking forward to changing the starter, so will check absolutely everything first.

Thanks for the help.

 

Resolved.

After checking and cleaning everything I thought I could, I was resigned to changing the starter. But given the hassle that would be, I took it into an auto electrician to check it over. Turns out the wire connecting the solenoid to the starter was loose (it looked ok to me, but I only visually inspected it).

Now all sorted. Thanks for all the ideas and help (and discouraging me from changing the starter) on this one.

 

Someone recently found the upper ( furthest away from the starter motor ) large terminal post on the solenoid loose on the inline 6 which is in the below pic

Yours was the short starter motor pigtail

To prevent this from happening again a 13 mm nylon lock nut ..............................

 

The problem is back again, this time I’m going to have a look with the exhaust of myself. But I’m going to get a spare starter, so if I can’t find anything else, I can swap it while I’m there.

Having some trouble finding a starter at a good price in New Zealand. Does any one know if the starter from a x306 (dcb6923e) will work instead of the x305 part (dcb6924e)?

 

The X306 is the long wheel base X300 with the same inline 6 engine , never with the V - 12

The inline 6 supercharged engine ( same engine block ) uses a different GM transmission that it mounts to which is the same transmission on your V - 12 , the engine / transmission bell housing is the question

The X308 has the V8 engine

The mounting holes pattern has to match and I have an extra normally asperated inline 6 starter in the garage to look at to get a pic of the pattern for a normally aspirated inline 6 which you don't want

the small pinion gear on the starter adaptor nose may be different also along with it's extension reach

The X300 starter as original manufacture is a Bosch 110 series with the final adaptor nose ( that comes as the starter assemble when you purchase one )

You will see a longer Bosch # stamped on your starter motor barrel section , the # may ( ? ) Include the 110 as mine does

You may ( ? ) have the option of swapping the nose adaptor piece out with a new or rebuilt starter motor barrel of a 110 series

You will have to use the specific attached solenoid for your model of which your currently installed is questionable and may be the source of your current symptoms

Bosch does make a solenoid with their # stamped on the solenoid that is painted black as off brands are silver , I wrote it down somewhere before I put it on my inline 6

I had my starter assembly all the way apart looking at the electric motor brushes so no big deal

The solenoid attach screws may be loctited in so a impact tool may be needed before messing up the screw heads , heat helps

 

Thanks for the info. Ideally Jaguar would just publish the key dimensions, I’m sure I would be able to find something suitable.

Some websites indicate that there’s compatibility between different starters from different models, but it’s hard to find anything conclusive enough for me to take a risk.

 

The information that I have may be confusing in the last post as I presented it

Probably your easiest and best bet would be to take the starter assembly you have that does fit to a alternator / starter shop and have them check the starter / solenoid assembly and maybe they would have a replacement equivalent information source

I believe you replaced the starter assembly before

Fortunately, your V - 12 may ( ? ) be the same Bosch 110 series starter as the inline 6 and many other cars so you can do some swapping around

in the end the Body Processor Module must provide a ground to close the starter solenoid relay

The starter solenoid relay has 2 fuses and their power sources, so it would be a look into .........................

Editing

The fuse for the control half of the relay ..............# 12 / 10 amp right engine bay fuse box . this fuse requires that the right fuse box relay ( ignition positive relay ) close

This ignition positive relay closing is dependent on the ignition switch connections being clean and secured

the path between the ignition switch and the right engine bay fuse box relay passes through the inertia / crash switch with the 2 white wires being bridged

In the worst case the replacement of the ignition switch does not require removal of the key barrel or a new key

The fuse for the power through the relay ............. # 3 / 25 amp left engine bay fuse box _ this fuse is hot at all times directly wired to the battery cable as it runs around the car

You don't have a rotary position switch mounted on the transmission wired in between the BPM and the starter solenoid relay with your V - 12 GM brand transmission combination like on the more common normally aspirated inline 6 with the ZF4HP24 transmission

But the starter / solenoid assembly is electrically equivalent to the inline 6 , just the fit may and most likely be different

The pinon gear in the nose of the starter is important that it is correct

Oliver Marks may have some more information for you with his resent V - 12 starter replacement by himself and the sketchy understanding I have is a model year / VIN # difference between your 2 , V - 12 examples although a year different as his is a 1996

Your chip in the key as immobilization is something we do not have in the USA until the 1998 X308 model ( V8 )

 

I think because the relay is sending power to the solenoid reliably, I’ll need to get a good look at the starter solenoid (which isn’t engaging). There’s still a chance there’s another loose wire, but I’ve tried pretty much everything else.

I’ve ordered an aftermarket gear reduction starter that I think will fit, and will drop that in even if the starter is fine.

Will let you know how it all goes.

 

The starter solenoid relay may be getting the correct ground command to close it

Even though it is closing the power contacts inside can be burnt limiting the current to close the solenoid

Swapped or replaced ?

The ignition switch which provides a ground path command to the BPM so it can provide it's ground to the starter solenoid relay is easy to check

It's not the most confidence building as the pin 5 to Y on the switch connector is a momentary contact so it will waver on your meter

But if the ignition switch through the pin 5 to car frame ground is not up to snuff it will affect the starting system

I found green corrosion on my pin 5

 

Yes, I’ve swapped the relay, but not checked pin 5 ground, I’ll have a look at that.

 

The pin 5 to car frame ground must be as close to Zero as can be , the ground stud is somewhere that has the possibility to have been disturbed

You can lift up on the connector mounting in the dash to bring it out to you

Let me get the other pin # for when you rotate the switch

 

Pin 1 to 5