ABS Issues - Help

[ng4xjs]

Last night the ABS and low pressure warning lights cam on whilst the car (XJS AJ16) was parked outside my garage with the engine running. Hard brake pedal so no ABS pump. Did the obvious like tap it to see if it was just sticking. Came and went at low power intermittently. Checked the 30A Fuses in the passenger footwell. Okay.

No voltage at the motor, not quite true, 0.6V. I'm trying to work out other possibilities and can only think of a relay. I can find reference to a yellow one but just cannot locate it. To my way of thinking a low voltage might be the result of such a failure. Hand on heart, I'm no electrical engineer, can do the basics but any thoughts greatly appreciated.

Thanks
Nick

[Brakebuster]

hard pedal usually indicates that the nitrogen bottle has failed

this stores pressure and assists the braking , this bottle is a sphere in the engine bay and might be on the top of your brake mechanism, its on the opposite side of the engine bay in early ABS XJS's

the quick way of testing is to turn on the ignition to position two , and the ABS pump should charge the sphere, if it doesnt work at all or charges for longer than ten seconds, then this can lead to the sphere be at fault , replacements are not cheap , though fitting is fairly easy ,

the other issue could be the charging pump, if this is heard running, then it should be fine, if it doesnt run , it could be the pump or fuse , or usually the pressure switch mounted by the sphere , this is a complex switch and is not repairable, and replacement is the only way forward

i hope this points you in some directions


oh , and check the brake fluid level before all of the above

BB

[ng4xjs]

BB – Thanks for your reply. I’m sure the sphere is charged. Up to this point it only took about 10 seconds to energise in the mornings on start up.

My problem is that I cannot get the pump motor to run. Seems I only have 0.6V at the connector to the pump. Fuses okay so I’m guessing it’s the relay. I’m struggling to find. Also and I don’t know if is related or not. On the forward fuse box on the inner wing I have a 20A fuse which has blown. There is no reference to this fuse in any of the wiring diagrams I have.

Thanks
Nick

[dhdove]

Nick
Re fuse identification, surprisingly I have often found the owners handbook to have the best info on what fuse is where......
Have you looked in there?

TonyS

[ng4xjs]

Tony – You are absolutely right. I think my problem stems from the fact that this particular car is Japanese spec (although I’m hard pressed to find any real differences apart from the odd label).

I’m now thinking that the problem is the ABS pump relay which in turn is zapping this unidentifiable 20A fuse in the forward left hand side fuse box. If it is it all makes sense. I’ve ordered up a new relay which will be here tomorrow, so I’ll know then. Otherwise I’m stuffed and back to the drawing board!

Thanks
Nick

[ng4xjs]

I'm really stuck with this now. I've replaced the pump relay. I've checked the ECU (in the boot) relay. I've supplied the pump with an external source of power and it works fine. Don't know what else too do.

The only very small lead I have is that when the problem first presented itself there is a 25A Fuse in the forward LH front wing box that kept blowing. It has also stopped blowing and so I'm thinking the two issues are related. But to compund the problem there is no listing absolutely anywhere Ithat I have access too that lists this fuse. I've even conversed with my local main dealer who are always extreemly helpful but they too cannot help. Does anyone have access to the Japanese spec wiring layout as this is the only other option I can think of.

Alternatively, anyone know of a good mobile auto-electrical engineer in the Gillingham (Kent) area.

Thanks
Nick

[steve_m]

Don't you just love Jag electrics? Spent 3 hours this afternoon trying to figure out why I have 1 front side light and no dipped beams. Still figuring.
Check this link out, there is a ton of useful and useable (pdf format) information.
It just takes a while to find the exact right section that you want but it does give the location of pretty much all of the relays.

http://www.captainjaguarscathouse.com/E ... 0Guide.pdf
Now all I have to do is hunt around for the headlamp dip relay location for my 86 cabby.

[ng4xjs]

Thanks guys. Twas a combination of the pressure switch and sphere, all now working. Thanks also to Paul and Keith for their interest.

Best wishes
Nick

[Brakebuster]

glad u got it sorted ,

as in my original post then..........


BB

[ng4xjs]

Okay so you were right. I hadn't applied the right logic when looking or no power at the pump. I've learnt

[keithbaker]

Glad to hear you got it sorted, Nick, and good to meet up the other day.