Hey guys I've got this 1991 xjs v12.

I'm finally getting around to doing some work on it and making it road worthy.

Yesterday was the maiden voyage for this cat, all was going well at first (except for the bad rack and pinion) Then I stopped at a gas station.

When I got back in the car the brake pedal was rock hard and I had almost no brakes at all.

This has happened before in the shop when I was moving it around and it had seemed to fix itself.

From what I can tell It seems electrical, such as a faulty connection.

I have gone through and bench tested all the relays and all is well.

I pulled all the connectors and ensured they were well in contact with each other.

Is there an electrical switch that sends the signal to the pump?

How could I bench test the abs pump to ensure it's working properly?

Thanks,
Alex

 

I had a similar thing happen to my 85 XJS. I'm not sure how much mechanically changed along with the remodel of the 91 model year. But my problem was congealed fluid in the reservoir. There is a small screen in the bottom to filter things like that out, after cleaning the screen, reservoir, and flushing the whole system it never gave me a problem again.

 

Sounds more like a failed/disconnected vacuum booster.

 

Thanks Adam I'll give that a try, the brake fluid is very dirty so that seem plausible.

On these they have an integral abs system with a pressure pump and accumulator that feed pressurized brake fluid to the brake lines, as does a vacuum boosted system.

I have no idea how the integral system might be better.

In my opinion it is completely idiotic in comparison to a vacuum system.

I much prefer things that are kept simple and effective.

 

Update:
Everything is is working order.

The abs pump is now getting a signal but It does not turn on.

When I bench test the pump with 12v direct from the battery it works but the 12v comming from the plug does not turn the pump on.

Any advise?

Thanks
-alex

 

I'm with Mikey. Check the vacuum booster pneumatic connections and check valve.