[Diy_efi] Jetronic - RFI - ABS gotchas

[Jason M.]

One vehicle you might consider as a donor is the early 90's 
caprice/impala/roadmaster/etc..  The ABS pump is essentially a stand alone 
unit.  It's only a 3 channel system, left and right front and rear. 
Essentially you'd only want to use it on a rear drive or all wheel drive 
vehicle.

For the caprices there is a master cylinder, a proportioning valve hung from 
the master cylinder, the ABS unit is mounted to the steering box, then of 
course the normal brake calipers, wheel cylinders etc. used on full size 
cars essentially unchanged since the early 80's.

Only real change to any of the brake components is the front rotors are 
machined and fitted with reluctor rings.  The rear sensor is mounted to the 
pinion internal to the differential.

The ABS Pump unit is also self contained, pump, electronic control etc is 
all right there.  Also has self diagnostics.  All fittings on this unit are 
ISO "bubble" flair.


I've also had some experience with a rear abs 1988 ford F350 at a previous 
job.  It didn't work, was an old nelson tree truck with 300,000 miles.  We 
had it for another 150,000 before the little abs unit started leaking 
everywhere so we just ran new brake lines bypassing it.


----- Original Message ----- 
From: "Lee M. Lemoine" <llemoine at gmail.com>
To: <diy_efi at diy-efi.org>
Sent: Monday, March 06, 2006 12:05 PM
Subject: Re: [Diy_efi] Jetronic - RFI - ABS gotchas


In my subaru, the proportioning takes place in the ABS unit, which is stand
alone from the master cylinder, and the exact same unit you see on that "
Howstuffworks.com" link.   I can take pictures if you'd like.  Either way, I
can tell you that ABS and non-ABS brake pads are no different...   Brakes
will continue to be brakes, in fact, the only difference between '88 and '90
and '91-94 (in j-body years) was the slightly larger diameter brake rotor,
which was curing the 'warped brake rotor' issues on the V6 RS and Z24
models.  (its .45 inch larger diameter, and 1/4" thicker)   Either way, the
interesting part is that the calipers interchange -- the most effective
braking for that car comes from a slotted (smaller) rotor with the (lerger)
caliper and pad on them.  I have done this swap without incident on my car,
and ABS still functioned...  (until i melted the ABS unit with the radiant
heat from the turbocharger / exhaust piping)

Yes, the REAR-only ABS systems use a different modulation setup...  its more
just a 'dump it if it locks' mechanism...  not very high tech...    Some
GMC3500 trucks built in the mid 90's had this.  I can recall a '96
particularly, with a 454, and REAR only ABS.  Had a regular master
cylinder... not sure where all the recirculation stuff was..  I no longer
work for that company, otherwise i'd go take some pics..