torchred96

My current project. The car is a 91 zr-1 with and selective ride control (rpo fx3), 135k miles. No factory manual and no tech 1 or similar yet so initially I will be flying with just a multimeter , information available elsewhere on the internet and basic hand tools.

I've been through many of the systems on this car and upgraded it as I went along. The abs system is one of the last things I'd like to get back in working order. I know many would disable the system and leave it that way, but without getting into that debate, I've decided I would like to restore it to working and/or better function. My abs system appears to have been purposefully disabled. I won't speculate on deceptive motives and will assume it was because of cost to repair.


Where to start. signs and symptoms:
1: no abs related lights on the dic;
2: brake light on the dash is not on;
3: abs does not go through it's self check sequence;
4 :no abs lights come on in the dash when ignition is turned on for self check;
5: no whirring noise from the pump motor turning on since I've owned it;
6: no codes displayed on the dic after grounding pin A to pin H of the ALDL connector.
7: spongy brakes (this is only after developing a leak in the rear braided brake (zr-1 only), so that repair is also in order.

Opening up the rear storage compartment is daunting when first looking at it, so I figured some study is in order. UGH..Did the factory actually make that mess? This is not something I would have expected...looks like a massive hack job. My old 96 was actually pretty nice back there but it was untouched (different systems obviously too).

What I found:
1: abs computer relay in the front right of the compartment had the orange wire corroded off the relay, just hanging there beneath the relay.
2: one wire was apparently purposefully snipped going into another connector
3: abs ebcm connector was not plugged in and just laying on top of the computer...looked connected but it was unsnapped. confirmed that it doesn snap down and is not physically broken.
4: one of the harness connectors has a diode placed across the terminals and is then has electrical tape over that (apparently this is factory, but initially I thought it was a hack)?
5: main red positive cable was disconnected and the male connector was missing from the opposite end (It looks like a cheap connector so I doubt it's factory (doesn't look like the negative connector which is nice) it is crimped poorly).
6: Main ground wire was disconnected (factory connection)
7: Pump has some corrosion on the outside and on the line fittings have some rust. UGH. My thoughts at this point..water damage>? Nothing in the carfax about that, but who knows. Nothing else on the car give me the impression that it was ever flooded.
8: Braided brake line hose at the master cylinder (the one going to the rear brakes is leaking enough to have to fill it every 3rd day with no driving.
9: Disconnected all electrical, including battery, then applied 12v to the abs motor...click, but nothing else, motor did not turn on as I had hoped.

If anyone wants to see what I am doing, and give me tips and information as I go along, I would really be grateful for the help and I will do my best to take pictures and answer your questions and results of your tips/tests. In the next post, I will take pictures of what I am doing and have done up to this point. I've actually made some progress, but decided to regress and document so others can benefit, regardless of my outcome.

One last thing, I'd like to try as much as possible to keep statements out that are not factual. For example, I don't want to say that 90 and 91 are identical systems or even that the standard and zr1 systems are identical until I know for sure they are. There is conflicting information on the web that I found and I do not have the manuals.

Eike

If the '91 service manual would help, send me a PM ...

torchred96

torchred96

Okay, as you can see, I have a big mess in that compartment. There are broken wires, corrosion, etc. My first thought was that I'd like to test the relays, clean up the harness and fix any broken wires. It was a fairly easy job once I figured out how to release all the connectors. A flat head screwdriver pushes the tabs down and they sort of pry out very easily.

One interesting note. The fx3 computer harness (all the blue connectors) is connected to the abs computer harness with only 2 wires but the whole thing gets taped together. At this point, information I've read says that the fx3 in this year uses vehicle speed input to vary the shock settings and I don't know if those are the 2 lines it gets that information from. Does anyone know what those two wires do? I was thinking maybe at least one wheel sensor, just a WAG though.

I will be hooking up 12v to the pump motor ..that fat red wire and the fat black wire to see if I can get the motor to spin

My next plan after that is to clean up the harness, re-tape it and fix the broken wires going to the relays.

There are 4 relays in this compartment, the big long one (overvoltage protection rely) is clipped to the front rail between the abs computer and the fx3 computer. It provides voltage to the abs computer, hydraulic pump motor relay (on the top of the pump.

There are 2 relays on the pump itself, one the motor, the other the solenoids within the pump.

That leaves one more relay, and I don't have a clue yet what it does. As I find out, I will edit this post and put more factual information here.

I know this is kind of a backwards way of doing this, but since I had no lights at all, when I grounded the aldl pin H to A. I needed to at least get the system up before I can get any codes at all.

Update:
At this point, I have applied 12v directly to the pump motor..thought I'd give it one more chance (all harness were disconnected and both relays on the pump removed. Also, the battery was disconnected too just to be safe). No luck, a nice spark but the motor does not turn. I ordered a used one from Ebay fairly cheap..hopefully it will work. Even if the motor would have turned, it would not have guaranteed the solenoids would be be able to actuate when power applied to them. Anyway, motor doesn't turn so I will be removing the pump and awaiting the new one. I'm guessing that either the armature of the motor is stuck, or perhaps a piston that the eccentric on the pump pushes on is stuck...either way, I have another pump on the way ($105 shipped) andt it has the harness and all the relays etc too (at least the pictures on the bay shows them).

In the mean time, I will continue with familiarizing myself with the various relays, testing them, fixing the harness and hopefully learning more details about how it all works.

As a stopgap to the leaking braided brake lines, I will temporarily make 2 hard lines to take their place so at least I can get some testing performed when the new used abs pump arrives. I don't know of a local shop or even supplier of the parts for those brake lines so for now, hard line replacements should work ok.

torchred96

Thanks Eike, i'll keep it in mind, right now I'm just doing the basics, then I'll put it together and see if I get the computer to power up and hopefully either get some codes or better yet, it will just work

Right now, I'm trying to track down a source for the stainless steel braided lines that exit the master cylinder. If anyone knows who can make them, they both appear to be the same part. These are specific to the zr-1 for some reason, something to do with installing the engine necessitated ss braided lines. My luck, one of them is leaking so I'd like to replace them both if I can find a source. thanks

torchred96

Here is the completed and redone ABS well. That modulator pump is from a mercedes e320 I believe and the wiring was a little different.