Hi Everyone,

It has been a tough winter for me... Fell over the stair rail moving furniture and more recently broke several toes... How the hell did I do these things that are not Jag related ??? lol Anyway. I need to work on both my Jags but my priority is to find the short in my 89 xjs ABS system. When I last left off, I was blowing the 30amp fuse below the passenger side console (1 of 2 ABS 30amp fuses). I have been told by several that I probably have a pinched ABS wire from the Accumulator to ?? so far, I've unwrapped a bunch of wires in the engine bay to no avail !!! It appears, without cutting wires and testing, that all is ok at least to where the wires enter beneath the brake reservoir on the drivers side heading to the ??

So, anyone been there done that and has some good suggestions will be appreciated !!

Might there be another explanation or two ??

Thanks for viewing.

Ken in Wild and Wonderful WV..... by golly !!

 

Check post #28 in this thread.

https://www.jaguarforums.com/forum/x...2/#post1525529

The problem will almost certainly be a pinched wire in the harness from the ABS pump (NOT the pressure switch blue connector).

The black connector on the side of the ABS pump mounting bracket. The wiring goes under this bracket.

 

Hi Ken

It may not be a 'pinched wire' on the ABS, as it could just as easily be a Faulty Foot Brake Switch.

So give it a Test with the Meter to make sure that its not broken, or shorting out somewhere.

If you decide to remove the Brake Switch in order to Test it. (only one bolt)

Its best to take a Photo of how it goes, as while its deceptively simple putting it back can be a bit of a 'Head Spin' if you forget.



It could be a Faulty Foot Brake Switch or a Wire shorting out down there.
Don't remove the ABS access it from inside the Car.

 

which is the color of the wires you are suggesting: orange, blue or red ??

 

If it's blowing the 30amp fuse then it is almost certainly a pinched wire.

One 30a fuse powers the ECU and the other powers the pump. Determine which 30A fuse is blowing, it will probably be the pump fuse. If it's the ECU then the ECU is probably toast.

 

The pump connector is the black connector on the left in your photo and the wire is Brown/blue

 

A faultfinding tip - use an incandescent light bulb 20watts will do (in this situation) and solder a couple of wires to it with spade connectors on the other end. Remove the 30amp fuse and insert the light.

The light will glow when there is a fault drawing excess current. Will prevent damage to upstream components and saves replacing fuses all the time.

 

Warren,

Sorry, I must be getting dense at 75, perhaps in a few more years I'll get better ?? lol
I was referring to my colored arrows in the photo to ask where the brown/blue wire may be located. The blue arrow wires do not readily show any pinched wires unless it is in the head of the connector where the wires immediately bend 90 degrees.
Thanks,
Ken

 

Warren,

I found the brown and blue.... Not blind, just forgot where to look.... Will trace it, thanks.
Ken

 

Warren,

Where does the brown/blue wire terminate after it goes through the engine bay by the brake reservoir ??

Do you have a book or online source that provides all of the wires, colors and where they run ??

Thanks,
Ken

 

It goes to Pin 87 of the ABS relay, a diode and the ECU.

I forgot about the diode, if this id short (a common failure) it will blow the fuse as well.

Here is the electrical wiring diagrams.

 

My ABS relay does not look good (It has black on the bottom) but I've searched and cannot find how to test... Where did I not go ??

Thanks,
Ken

 

Remove the relay from the car, apply 12volts between pin 85 and 86, use a DMM and measure resistance from pin 87 to pin 30, it should be ZERO. remove the 12volts and resistance from pin 87 to 30 should be infinite.

I doubt the relay is the problem though.

The problem is going to be either -
The ABS pump
ABS wiring harness to the pump
Or the diode, which is shown under the main valve in the circuit diagram.

My first guess would be the wiring.

 

Warren,

I'm getting denser than ever. I had just checked my relay and it is fine, black spots and all. it was the relay mounted on the top left of the engine bay on the driver's side closest to the radiator. Unless there is another one or this one is in the wrong spot !! I need to check the main relay in the trunk.... Also, what diagnostic equipment can you plug into the diagnostic socket from the ecu ??

I'm pretty certain that it is not the pump as it comes on for a second or two just before the 30amp fuse blows.

 

just found that the diagnostic plug from the ecu had something to do with checking the fuel mixture or something similar... Thought it did not have any OBD or other checker.
ken

 

Still could be the pump, if the pump bearings are bad causing the pump to labour this could blow the fuse.

You can test the motor with a battery across the motor terminals directly. Remove the black plug and use alligator clips to connect the battery, it would be advisable to use a fuse or incandescent light bulb to prevent the motor going up in smoke.

 

Warren,

Sorry, please refer to my earlier photo and I would appreciate retraining me on what goes where. I must have forgotten how to do this.... !!!! positive to this and ground to that !!

Thanks,
Ken

 

I have circled the ABS pump connector in red. The other connector is the switch and can not cause the 30amp fuse to blow.

Disconnect the car battery before you start.

Disconnect the ABS plug and grab your trusty DMM, put it on Ohms and meter the Brown/Blue wire to ground, it must be open circuit (NO continuity), if there is any reading on the DMM then you have a problem in the wiring loom.

If the loom is ok then Leave the connector disconnected and the end attached to the bracket apply 12 volts positive to the Brown/Blue (with a 30amp fuse) and neg to black.

Don't leave the battery connected longer than 30seconds, if the fuse does not blow and the pump runs then you good here.

 

Well, no continuity of either brown and blue or black. Motor test is fine, runs well. So where do I go to check the diode ?? And, my furu, what next would you suggest ??

 

You did meter the loom side of the plug NOT the motor. The black wire in loom should be connected to ground.

I'll have to put my thinking cap on.