The pump quit running today. While my wife was trying to go somewhere, of course. She had driven it earlier with no problems (although it might have quit while she was driving it, and she didn't notice the lights - she says, "They're always on." They aren't, actually, although sometimes they stay on until you're backed out of the driveway).

Anyway, after getting off work, I established that the pump wasn't getting power. I traced the power wire to the relay on the left side of the firewall and established there was battery power to the orange wire, no power with key off to the others. With ignition on, there was power to the small brown/red-striped wire, but none to the gray/red-striped wire (I might have those two mixed up - I didn't write them down while checking). I only have a '91 manual, it told me to check Fuse 8 if I didn't have power w/ignition on to Terminal 2 - Fuse 8 was good. So was Fuse 9, which the owner'* manual and fuse table said was for the ABS pump.

I left the ignition on, and pretty much giving up for the time being, plugged the relay back in - and the pump started running. If I recall correctly, it was the 2nd time I had plugged the relay back into the harness during this process.

So, do I have a bad or weak relay? Were the terminals just dirty? They didn't look dirty.

What is the gray/red-striped wire for that goes to the relay (assuming I'm remembering which one didn't have power)? The '91 shop manual doesn't show another circuit at the relay.

My wife just called to report it quit again, one short trip to Ace Hardware.

I have found sometimes that an old enough relay will have carbon build up on the contacts. Therefore it won't always supply power even though you can hear/feel it actuate. Consider replacing the relay and this time..add a dab of dielectric grease to each contact. They put it in and take it out 5 times. That will clean up the contacts if they are dirty.

Sounds like a plan.

At least a start if nothing else.

New relay from the dealer is now installed. $11, pleasant surprise. Of course, the old one had started working again so the accumulator was charged, the car was blocked in the driveway so will have to wait until later to see if it continues working. At least backing up a few feet and driving forward a few times, no issues.

I thought they stopped using the Teves system in 1990 and went to a standard system in 91?

IIRC that'* about right.

You know how it is with documentation and reality.

And, the new relay didn't help.

Well, I went back out this evening to try some more diagnostics. As soon as I turned the ignition on, the pump started running. Before I could do much, it got up to pressure and shut off.

Okay, this is probably too simple to be true, but is it possible the gray/red-stripe wire is the ground for the relay, controlled by the brake control module? I tried checking for ground, but that was after the pump shut off, it was open to ground.

Looking at the book, I'm sure that'* what it is. It shows a switch to ground internal to the controller on the other side of the relay coil.

Maybe the problem is with the pressure switch.

The control module can be scanned, right? Just not with an Auto Xray.