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Re: ABS madness, continued (LONG)
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Posted by Jeyi [Email] (more from Jeyi) on Wed, 21 Jan 2009 14:33:32 Share Post by Email
In Reply to: ABS madness, continued!, Jeyi, Wed, 21 Jan 2009 13:20:30
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OK, I see that there's not a simple fix. I applied external voltage to the pump relay and it seemed to work OK. So that wasn't the Thank you Baby Jesus easy fix that I just thought it might be.
(Maybe an internal diode in series with the relay coil kept me from getting a resistance reading.)

So then what I did is that I pulled both the relays, and ran a bus wire between pump relay female terminals (inside the relay box), and the ABS pump came on as expected. I left the pump running for no more than five minutes seeing if it felt warm or maybe started smelling bad, which neither thing happened. Brake fluid light went off.

I disconnected the bus wire and re-inserted the pump and main ABS relay. Then I tried the pedal, thinking I might have built up some pressure in the bomb, but the brake fluid light came on again after only one or two strokes.

So yes, maybe the replacement accumulator wasn't any good. But I still don't think that was the source of the problem. Even a totally failed bomb should work more than two strokes and the pump shouldn't shut down after three to five seconds in any case.

I think the problem was more likely in the pressure sensor, apparently on the pump body, which is evidently what controls the voltage to the pump relay.

But now I discover --to my horror-- that nothing I do makes the pump run again, either with the relay back in place, or trying once more to use the bus wire with the pump relay out. I don't think that the five minutes maximum that I had let it run with the bus wire in would have been in itself enough to burn out or damage the pump.

As a secondary issue, when I checked for voltage at the female terminals 85 and 86 for the main relay, I got zero in every case with the pump running or not and the brake fluid light on or not.

Also the pedal itself feels not quite right. I started the engine and again, this time I can't get the pump to run even for previous five second cycle, nor can I get the brake fluid light to go off.

Again, none of the ABS box fuses have blown.

BTW, I also bought a ABS ECU from a wreck, but I haven't tried exchanging it yet. From what I understand, the brake assist function (remember, in 1991, there was no vacuum assist for the brakes, only the ABS pump and bomb system. SAAB evidently went back to

Ideas? I'm beginning to wonder that maybe I have to face up to the $$$ replacement of the entire hydraulics unit (ABS pump, reservoir, master cylinder). But the part doesn't even seem to be available anymore.

I'm seriously freaking out now.

posted by 24.1.225...
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