ABS Retrofit

#1

After flat spotting and ruining 5 tires last weekend at CMP, I’ve decided to prioritize retrofit of the ABS back into my car. Today I removed a complete system from a donor car that had working ABS a few weeks ago before I removed the engine for my Dad’s car. Getting the wheel sensors, brake lines, and the pump removed was a breeze. Removing the wiring harness was a royal pain in the a$$. My plan is to strip the harness of everything that doesn’t appear to be ABS related before installing in the fish car.

Any helpful tips would be greatly appreciated! I’m planning to get this done next weekend if all goes well…

#2

I’m making progress on this job and it appears to be going okay. Last night I separated the ABS portion out of my new wiring harness. I had a giant mess of wires running throughout my garage. It appears that the ABS only has four external connections (ground, switched power, alternator input, and the brake pedal switch input). With everything hooked up outside the car on my garage floor, I was able to make the ABS light iluminate while checking with a 12 volt power source. This is encouraging…

After I prepared the new harness for installation, I removed the dash and inspected the harness currently in the car. This was not nearly as encouraging. The existing ABS harness is still present, but everything is a mess with wires cut, spliced, and running everywhere. My plan is to isolate the old ABS wiring, remove and install the new harness in place. To do so, I’m pulling the complete harness out this evening.

I wonder if my car will ever run again? Actually, I don’t think the engine requires too much to operate. From what I can tell, all of the required electrical connnections (alternator, O2 heater relay, coil power, fuel pump relay, and starter solenoid) all run through the C101 connector. Everything else is for ancillary devices that aren’t necessary on a race car.

#3

At the next race, can you point out the wires I need so I can remove the rest? :cheer:

#4

Is it allowable to remove the wires that aren’t needed? I’ll have all of them, they’ll just be from two different harnesses.

#5

Richard Bratton…kinda like “Star Trek,” going where no man has gone before.

Good luck, I really can’t be of any help on this adventure.

RP

#6

Last night I separated the ABS and other nonessential wiring from the harness in the fish car. It required a second set of hands to pull the harness while I fed the wiring through the firewall in the driver side footwell. My Recaro racing seat was surprisingly comfortable while mounting it upside down…

Then I opened up the underhood fuse box. After trying to isolate wires before cutting the nonessentials for a half hour or so, I decided just to cut everything and splice back the essentials. I was able to isolate the windshield wiper wires and the starter signal wire (black/yellow), but I cut everything else. After that, it’s fairly easy to just pull out the nonessentials and discard. The stereo wiring is quite impressive; how many speakers did these cars come equiped with anyway? What’s copper going for per pound these days?

A few tips… A Sawzall works great for cutting large groupings of wires, but make sure you either flip the kill switch or disconnect the battery before cutting. It still might be helpful to have a fire extinguisher handy!

After cutting all of the wires, I was a bit concerned that I would never hear the car run again. So before I neatly wire it back up, I decided it would be best to test all of my connections. With only a few jumper wires spiced into the few essential wires in the C101 connector, it started and ran fine. The wipers work too!

I plan to integrate the ABS wiring tonight and plumb the brake lines over the weekend.

#7

I’m not gonna lie. I am very impressed.

#8

When its all said and done (and it works) would someone be so kind as to do a write up and tell us what can come out and what needs to stay? I would love to get all of that crap out of the car.

Thanks,
Jason

#9

Okay, everything is installed, but I can’t make the ABS light go out and the system isn’t functioning. After working on it all day yesterday, I was about ready to throw in the towel. Reading naysayer chatter this morning on the “cars for sale thread” about how SCCA cars don’t make good spec cars motivated me to work on it all day today. Thanks Robert and I WILL get this working! Like Ranger’s engine struggle, this is just a battle of will and no ABS system is going to beat me. It just may take a while to figure this out and I’ll keep trying until it works…

That said, here is the situation. Electrical and hydraulics are all installed.

Things I’m certain of:

  1. All four wheel sensors are good. Resistance checks out at ~1000 ohms for each (rears have slightly more resistance).

  2. Brake lines are plumbed properly.

  3. The main relay is good. I have three; only one works.

  4. Electrical connections are proper and wiring is good. Readings at the main ABS connector below:
    -Pin 1: Reads 14v with car running. Will not have voltage if main relay is bad.
    -Pin 10, 20, and 34: Ground.
    -Pin 15: 14v with car running. This is the charge indicator from the alternator.
    -Pin 25: 14v when you activate brake switch; no voltage with brake switch open.
    -Pin 29: .65v; this is the green red wire on the negative side of the warning light. Street car voltage was a bit higher at .75v. Warning light now on in both cars (I swapped a bad wheel sensor on to street car; otherwise system is functional).
    -Wheel sensors all measure about 1000 ohms (rears 1100ish); FL-Pin 4 and 6, FR-Pin 11 and 21, RR-Pin 24 and 26, LR-Pin 8 and 9.

Readings in my race car and street car were the same at all pins with the exception of Pin 29 as described above.

  1. The ABS control module is operational. I activated the ABS in my street car during a test drive yesterday and the ABS functioned properly. The ABS is currently not working in my street car because I swapped out the FR wheel sensor for my race car. On a second test drive with the known bad wheel sensor installed, the ABS light did not come on until I locked up the wheels. At the first sign of lockup, the ABS light came on and the ABS ceased to function. After validated my wiring, I swapped the control module over to my race car.

  2. The wiring/connectors is good between the ABS control module and the hydraulic pump. I did not test each circuit but did visually inspect each wire and the connectors.

Things that I’m not certain of:

  1. The condition of the two relays located at the hydraulic pump. I’ve swapped the known good ones off my street car, but I did have one wire hooked up incorrectly. Damage to the relays is possible but unlikely. The wiring issue was corrected before swapping control modules.

  2. The hydraulic pump condition is unknown. It looks fine, but I have not conducted the electrical test on each of the solenoids or valves.

  3. Is there any interaction between the DME and ABS control module?

Currently the ABS light illuminates when I turn the key to ACC and start and remains on solid. I don’t know what else to do other than validate the hydraulic pump relays are good and then to change the pump. Before I change the pump, does anyone have any ideas? Jim Levie, I need your brain on this one!

#10
#11

Does the ABS light come on when you turn on the ignition, go out when the engine starts, and then come back on before the car is moving? The cause of that could be a bad module, a bad ABS unit, or a wiring fault. Since you’ve proved the module works that leaves the ABS unit.

If the light comes on with ignition, but doesn’t go out when the engine starts, a wiring problem, bad module, or bad ABS relay are the likely candidates. In this case I don’t think it is the module and the voltages read tends to exonerate the relay.

If the goes out after engine start and only comes one when the car is moved, there’s a problem with one (or more) of the sensors. The simple test to find out which sensor(s) is the cause is to disconnect all but one of the sensors and drive the car. If the light comes on, that sensor is sending a speed signal to the ABS and is good. Repeat with each other sensor to find the one(s) that don’t cause the light to come on. Since the ABS module has no speed input besides the wheel sensors, if only a bad sensor is connected the module can’t tell the car is moving and thus doesn’t fault on missing speed signals from the other wheels.

#12

From a previous post it looks like you realize that the front sensors are, in fact, a R and L type of thing and they do not interchange.

Regardless if either was wrong or backward it would not have anything to do with the “arming” of the system at car start-up, but would turn on the light after you drove the car.

I’ve been having the light stay on in my car till it warms up sometimes.Low battery voltage? Although you are checking voltage, have you tried to let 'er warm up for a few muiutes?

RP

#13

Robert,

Start the car with a DMM connected to system power and see if the voltage changes noticeably between a cold start and warm. That could be a sign of worn brushes in the alternator.

#14

Jim,

The ABS light comes on as soon as I turn the ignition and remains lit until I kill the ignition. From your reasoning, it sounds like I have a bad hydraulic unit. How finicky are the two relays that are located on the hydraulic unit? Is there a way to bench test them? This unit came out of a running car that has been sitting at a local BMW shop’s yard, but was likely sitting there for a possibly a year or more. The brake system was untampered with until I removed the ABS. Are hydraulic unit failures common? I guess the valves could freeze up… Good tip on testing sensors. Another easier test, but not as conclusive, ist to pull the ABS control module connector and simply test the resistance across the pair or wires for each sensor. A sensor that doesn’t function properly will likely have an open circuit or strange resistance value.

Robert,

I was not aware that the ABS sensors have a left and right. From looking at pelicanparts.com, it appears that the rears are universal to each side, but the fronts are left right. Thanks for the tip!!!

#15

Richard, yes on the sensors…Right and left up front and same in the back.

If you criss-cross fronts or run two of the same you’ll get the ABS light-on after you drive at …say 10mph.

Ask me how I know and how long it took to figure it out.

RP

#16

I made that mo’foin ABS my biatch!!! After swapping the pump, the car started and the light went out. I’m hoping the bulb didn’t burn out. More to follow after my test drive…

#17

I’ve never tried to trouble shoot a bad ABS unit, so I don’t know if a change of relays would have helped. It sounds like it is working now and that is all that really counts.

#18

Doing a test drive at 10:00 PM probably isn’t the smartest thing I’ve done, but I just couldn’t help myself. Okay, yup, the ABS does in fact work! I was able to make the tires chirp at about 30 mph, but the ABS functioned and I didn’t get lockup!!!

I spent about two hours this afternoon verifying (again) that every wire had continuity and was working correctly. After that didn’t fix the problem, I swapped the pump over from my street car, hooked everything back up, and started the car. With the car running, I sat there staring at the light. For about ten seconds the light remained lit. As I was sitting with my heart sinking, thinking that there could absolutely be nothing wrong with the system because I’ve checked everything and was certain that all of the components were good, the light went out. It felt good… Not that this is really that big of a deal, but I’ve spent every night working on this for the last week and all day Saturday and Sunday. That being said, if I had a known to be good pump, control unit, harness, and four sensors, I could do the install in just a few hours after all I’ve learned during this adventure.

The system does have a few quirks that concern me a bit. Jim Levie, read this part.

  1. The light remains lit for about ten seconds each time I start the car. One time I started the car and started driving before the light went out. The light never did go out and I drove for about a minute. I stopped, restarted the car, and the light went out after about 15 seconds. Could this be an issue with one of the relays on the pump? Is this normal? It sounds like Patton has the same issue.
  2. The brake pedal seems a bit spongy. I bled the brakes using the 2 person method. To make it easier on the pumper (Stephanie), we bled the brakes with the car running. I filled the master cylinder 2 or 3 times (good thing I used the cheap stuff) and the fluid was flowing clear at all wheels. I’m wondering if there may be a bit of air trapped in the pump. I’ll bleed the brakes again and see if that helps.
  3. I’m planning to install a longacre warning light. I’m not sure of the wattage, but do you think this light will cause any problems?

To get my street car running again, well it runs but won’t stop very well, I’ll need a working pump and LF wheel sensor. Anyone got spares? Thanks to Robert for the tip on left and right sensors; that would have stumped me for sure, to Steven for providing electrical schematics, Jim Levie, Scott and others for various tips and motivation. I can’t wait to try this out at RA!!!

#19

I’ll bring you a used ABS pump at RA. Poke around ebay and see what a fair price for it is.

#20

FishMan wrote:

[quote]The system does have a few quirks that concern me a bit. Jim Levie, read this part.

  1. The light remains lit for about ten seconds each time I start the car. One time I started the car and started driving before the light went out. The light never did go out and I drove for about a minute. I stopped, restarted the car, and the light went out after about 15 seconds. Could this be an issue with one of the relays on the pump? Is this normal? It sounds like Patton has the same issue.
  2. The brake pedal seems a bit spongy. I bled the brakes using the 2 person method. To make it easier on the pumper (Stephanie), we bled the brakes with the car running. I filled the master cylinder 2 or 3 times (good thing I used the cheap stuff) and the fluid was flowing clear at all wheels. I’m wondering if there may be a bit of air trapped in the pump. I’ll bleed the brakes again and see if that helps.
  3. I’m planning to install a longacre warning light. I’m not sure of the wattage, but do you think this light will cause any problems?[/quote]
    The ABS light should go off when system voltage rises once the engine fires. A weak alternator might cause a delay in the ABS realizing the engine is running, or there could be a problem in the ABS module. The first thing I’d do would be to monitor system voltage and see if it is climbing once the engine starts. If the battery is charged system voltage should go immediately to at least 13.5v at idle.

Go find a wet parking lot or a sandy area and get into the brakes hard enough to activate the ABS (front & back). Then re-bleed to get out any air that had been trapped in the ABS unit. I’ve changed out ABS units several times and not had a problem with air in the unit, but then I use a pressure bleeder and go through a liter of fluid (for a total flush) following a master cylinder or ABS unit replacement.

A warning light for what?