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1993 G20 ABS issue, help please
#740001 September 01st 2018 3:42 pm
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My 1993 G20 had great brakes until I locked up when braking on a slippy road, ABS pump kicked in but afterwards the pedal travels almost to the floor before the brakes kick in.
This happened before when I locked the wheels up a few years ago and I disconnected and reconnected the battery and everything returned to normal...unfortunately a battery reset has not made any difference this time. I have no abs trouble codes apart from code 12 which is supposed to be there I believe and all fuses are ok. The pump runs ok when it does its self test. We are supposed to be heading to the european drag race finals in 3 days so I am starting to panic a bit..

can anyone offer any help or point me in the direction of someone who can ?

thanks
Robert

Re: 1993 G20 ABS issue, help please
GT390 #740002 September 01st 2018 4:30 pm
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OK need to know more ... I have a 93 Factory Service Manual.

Does the van roll, is there a wheel locked up, does the brake pedal pulse, does the abs light stay on ?


SUNSHINE VANS-VAN DIEGO
ADRENALIN BY THE GALLON & CHASIN RACIN
ONE FOR THE DIRT & ONE FOR THE STREETS
'93 CHEVY G30 454 4X4 SPORTVAN EXT 146" WB
'92 CHEVY G30 454 BEAUVILLE EXT 146" WB
Re: 1993 G20 ABS issue, help please
GT390 #740005 September 02nd 2018 8:30 am
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Ok, thanks for the reply, I also have the factory manual but have not found any info so far that has helped.
Van rolls and drives ok, no pulse from pedal just excessive travel, when you first press the pedal softly van begins to slow then the pedal gets softer again and goes almost to the floor before the brakes will come on harder, its driveable but feels horrible, abs light is coming on and going off as it should to do bulb test, never has came on and stayed on while driving. I finally found some info online about bleeding the pump and made two tools to depress the high pressure accumulator valves slackened the internal bleed screws and tried to bleed using the bleeders on the top of the unit..got good flow and no air out of the left bleeder but totally nothing out of the right...no fluid or air...when i crack open the left bleeder with someone pressing the pedal the pedal goes to the floor and fluid comes out as it should, crack open the right one and nothing comes out and the pedal remains firm...I have changed the brake fluid and bleed all at the wheels, getting good fluid flow to all wheels... I am starting to think something inside the abs pump has stuck..like a valve maybe...

Re: 1993 G20 ABS issue, help please
GT390 #740006 September 02nd 2018 10:38 am
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Have you checked the Proportioning Valve ? Under the master cylinder. I had one go out & with no codes, even stumped the mechanic ....No codes hmmm thats a tuffy.

https://www.google.com/search?ei=1f...0i7i30j0i13i30j0i30j0i7i5i30.zLwg9dTn9DY


SUNSHINE VANS-VAN DIEGO
ADRENALIN BY THE GALLON & CHASIN RACIN
ONE FOR THE DIRT & ONE FOR THE STREETS
'93 CHEVY G30 454 4X4 SPORTVAN EXT 146" WB
'92 CHEVY G30 454 BEAUVILLE EXT 146" WB
Re: 1993 G20 ABS issue, help please
frscke1 #740008 September 02nd 2018 12:10 pm
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Originally Posted by frscke1
No codes hmmm thats a tuffy.


Makes you wonder how things ever got fixed before we had computers.


Windows- they're what make a van worth owning!
Re: 1993 G20 ABS issue, help please
Reed #740009 September 02nd 2018 12:17 pm
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Originally Posted by Reed
Originally Posted by frscke1
No codes hmmm thats a tuffy.


Makes you wonder how things ever got fixed before we had computers.


That was back when it was just points N carbs ... ABS didnt exist . Now they have a censor on every thing.


SUNSHINE VANS-VAN DIEGO
ADRENALIN BY THE GALLON & CHASIN RACIN
ONE FOR THE DIRT & ONE FOR THE STREETS
'93 CHEVY G30 454 4X4 SPORTVAN EXT 146" WB
'92 CHEVY G30 454 BEAUVILLE EXT 146" WB
Re: 1993 G20 ABS issue, help please
GT390 #740010 September 02nd 2018 12:51 pm
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proportioning valve seems to be working ok its moving under pressure like it should and I tried bleeding abs pump again with a tool locking the proportioning valve ..still nada out of one side of abs pump..although good pressure at all wheels. As all was ok until the ABS activated I have to assume something stuck in the pump, a piston or valve...I am gonna have to head off on our trip as is as I am working 2 long days monday and tuesday, so will just have to drive with some caution...not ideal by any means..

with the locking tools in place and the internal bleeds open the pump should be a cinch to bleed but not in this case.. even tried a vacuum bleeder on it put it could pull no air or fluid through at all even with the nipple all the way out the brake pedal pumps up solid


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