What is this connector for???

I bought this Jeep a few weeks ago and the previous owner told me that the power brake booster is bad (pedal only travels half way and is rock hard - ABS equipped '91 - :nosmile Anyway, I was degreasing the engine bay today and came across this connector that is unplugged. I took some pics and it appears as if it runs to the power booster pump (I think that's what it is?). I'm afraid to plug it in in case something detrimental would occur - I figure he unplugged it for a reason. Is this what it goes to and could you think of any reason why it'd be unplugged? I thought that I read the pump would automatically turn itself off if it overheated / ran too long, etc. I'm starting to wonder if the booster pump is what was bad and not the brake booster/master cylinder assembly as I previously thought.

Also, if it indeed is the booster pump that is bad, anyone have a ballpark estimate on cost? What could i expect from a junk yard and how long / hard to install? What if I bought new and had a shop do it? I HATE working on brakes, but if it's going to be ungodly expensive for a shop to do it, maybe I'll suck this one up (assuming there aren't any special tools, etc required)

bump - trying to find out what that is on that side of the vehicle? Is that the booster pump? Is this the plug for it? I appreciate the help.

OK, the brake booster is the big round black thing behind the master cylinder, it's vacuum-powered (not electric) and nowhere near that plug. I had to read your first post 3 times before I figured out what the hell you were referring to as a "booster pump".

I don't know what that plug is. The only way to find out is to plug it in...I don't see it causing any harm. If something bad happens, just unplug it again.

anony91xj said:

OK, the brake booster is the big round black thing behind the master cylinder, it's vacuum-powered (not electric) and nowhere near that plug. I had to read your first post 3 times before I figured out what the hell you were referring to as a "booster pump".

I don't know what that plug is. The only way to find out is to plug it in...I don't see it causing any harm. If something bad happens, just unplug it again.

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I appreciate the help, but I know enough to know that the info you gave does not apply to my XJ. In the early ABS models (91, 92 for sure - may have been others) the brakes aren't vacuum operated - they are hydraulic. There is actually a booster pump that turns on and pressurizes the system (this pump and fluid take place of the vacuum portion of normal vehicles). It was a troubled system from what I've read and only lasted a few years.

gone postal said:

I appreciate the help, but I know enough to know that the info you gave does not apply to my XJ. In the early ABS models (91, 92 for sure - may have been others) the brakes aren't vacuum operated - they are hydraulic. There is actually a booster pump that turns on and pressurizes the system (this pump and fluid take place of the vacuum portion of normal vehicles). It was a troubled system from what I've read and only lasted a few years.

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You are correct the early ABS systems used a computer controlled "electric hydraulic pump' to operate the brakes. Sometimes when the ABS computer detected a problem people just disconnected it and the brakes when went to non-ABS but still depend on that electric pump to operate. The problem with that is when that pump fails you will have no brakes at all.
The master cylinder is not a pump, only a valve for that electric pump.
Newer systems have a real master cylinder as a backup.
If you plug it back in your "ABS" light will come on.
It can be a dangerous system when not properly maintained because there is no real backup system.

langer1 said:

You are correct the early ABS systems used a computer controlled "electric hydraulic pump' to operate the brakes. Sometimes when the ABS computer detected a problem people just disconnected it and the brakes when went to non-ABS but still depend on that electric pump to operate. The problem with that is when that pump fails you will have no brakes at all.
The master cylinder is not a pump, only a valve for that electric pump.
Newer systems have a real master cylinder as a backup.
If you plug it back in your "ABS" light will come on.
It can be a dangerous system when not properly maintained because there is no real backup system.

Click to expand...

Good info to know. The ABS & BRAKE light are on right now. So does that plug disconnect the pump or are you saying that is is disconnecting the ABS system? (which I believe is under the rear seat?) I don't think I have the pump's assistance right now b/c I don't hear anything run when I start the vehicle and the brakes are poor (but I do have some pedal - I can drive the vehicle, but reserve it strictly for the beach). I have about half of the pedal travel and then it is hard as a rock. I can move it a bit and that's the brake pressure that I get, so I guess tha I'm strictly mechanical right now - just compressing the fluid in the lines w/ my foot and that is what is actuating the brakes. I guess I'll plug it in to see what happens, but I was just wondering if it's a closed loop system - I don't want it shooitng fluid everywhere. I just wasn't sure if it used my actual brake fluid or if it has a seperate fluid of it's own?

It only disconnects the ABS the pump still provides your only stopping pressure.
There are some post about how to safely remove it by installing a NON-ABS master cyclinder.

langer1 said:

You are correct the early ABS systems used a computer controlled "electric hydraulic pump' to operate the brakes. Sometimes when the ABS computer detected a problem people just disconnected it and the brakes when went to non-ABS but still depend on that electric pump to operate. The problem with that is when that pump fails you will have no brakes at all.
The master cylinder is not a pump, only a valve for that electric pump.
Newer systems have a real master cylinder as a backup.
If you plug it back in your "ABS" light will come on.
It can be a dangerous system when not properly maintained because there is no real backup system.

Click to expand...

I don't know much about this setup, but something doesn't sound right. From what you're describing, there is no braking at all if the hyd pump fails. Doesn't that imply no brakes if the vehicle is turned off or stalls? This would never pass DOT, which requires a mechanical braking system that doesn't rely on power. Hydraulic or vacumn assist is fine.

lawsoncl said:

I don't know much about this setup, but something doesn't sound right. From what you're describing, there is no braking at all if the hyd pump fails. Doesn't that imply no brakes if the vehicle is turned off or stalls? This would never pass DOT, which requires a mechanical braking system that doesn't rely on power. Hydraulic or vacumn assist is fine.

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Thats what the hand brake is for.

OK read up here.
http://www.naxja.org/html/techarticles/uninstall_OEM_ABS.htm

lawsoncl said:

I don't know much about this setup, but something doesn't sound right. From what you're describing, there is no braking at all if the hyd pump fails. Doesn't that imply no brakes if the vehicle is turned off or stalls? This would never pass DOT, which requires a mechanical braking system that doesn't rely on power. Hydraulic or vacumn assist is fine.

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The backup is a pressure storage bottle called a accumulator but when it's empty your out of brakes.

Quit wasting time with that abs junk(got a complete set if you want it!) and replace it with a 96+ booster and MC. It will take a couple hours and you'll have better brakes than ever. I did it on my 91, had to reflare a couple lines (you can buy adapters) bleed the system and you are all set. I have a booster and MC from a 97 you can have for $60 shipped if you want to do it. You will find a nice write up on the changeover at Madxj.com too.

PS The aforementioned connector runs the abs pump assembly that's under the panel to the left of the connector. Not connected, NOT GOOD

Don't listen to any of these fools. That plug has nothing to do with the brakes. It connects to the flux capacitor. It transers the 1.21 gigawatts required by flux capacitor. Just kidding I have no idea.

Quote:

"Quit wasting time with that abs junk(got a complete set if you want it!) and replace it with a 96+ booster and MC. It will take a couple hours and you'll have better brakes than ever. I did it on my 91, had to reflare a couple lines (you can buy adapters) bleed the system and you are all set. I have a booster and MC from a 97 you can have for $60 shipped if you want to do it. You will find a nice write up on the changeover at Madxj.com too.

PS The aforementioned connector runs the abs pump assembly that's under the panel to the left of the connector. Not connected, NOT GOOD"

I second that...that ABS system is a fatality (yours!!!) waiting to happen....fix it with the vacuum booster/master cylinder upgrade...did my 90 in a day, and she stops on a penny.....with rear discs (coming soon!!) she will stop on a DIME......do a search, and you will find LOTS of info regarding this swap, but DO NOT DELAY...take care,

Bret S Gray
1990 XJ
1992 MJ

asatxj said:

Quit wasting time with that abs junk(got a complete set if you want it!) and replace it with a 96+ booster and MC. It will take a couple hours and you'll have better brakes than ever. I did it on my 91, had to reflare a couple lines (you can buy adapters) bleed the system and you are all set. I have a booster and MC from a 97 you can have for $60 shipped if you want to do it. You will find a nice write up on the changeover at Madxj.com too.

PS The aforementioned connector runs the abs pump assembly that's under the panel to the left of the connector. Not connected, NOT GOOD

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Okay, a few ?s about your swap. If I wanted to go that route, I have to remove all ABS equipment, master cylinder, etc. I then install new master cylinder / booster while reflaring lines (or where can I buy adapters?) and figuring out how to get the booster to connect to the pedal (is the '97 like the '96 in the article where you don't need to do a rod swap?) Anything else?

Why is it not good that the ABS pump isn't connected? Does that just mean I don't have ABS?

Can anyone confirm whether or not the claim in the other article ( http://www.naxja.org/html/techarticles/uninstall_OEM_ABS.htm ) about there being a lifetime warranty is true? If so, I'd imagine most people would opt for that rather than swapping boosters, etc.

And finally, should I just connect that connector then????

langer1 said:

it does nothing to warranty the lives of the XJ's occupants should the system fail at an "inopportune" time.

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Good point. Yes the system has a lifetime parts replacement/recall for the ABS pump and the actuator(master cyl). The reason they are recalled is the system is crap. Without the pump, no brake assist at all. You can stop, but not easily. You can just go down to the local dealer and have them patch it back up, but the system will fail again in the future. If it were me I would be swapping all that crap out. Best of luck to ya.

gone postal said:

Okay, a few ?s about your swap. If I wanted to go that route, I have to remove all ABS equipment, master cylinder, etc. I then install new master cylinder / booster while reflaring lines (or where can I buy adapters?) and figuring out how to get the booster to connect to the pedal (is the '97 like the '96 in the article where you don't need to do a rod swap?) Anything else?

Why is it not good that the ABS pump isn't connected? Does that just mean I don't have ABS?

Can anyone confirm whether or not the claim in the other article ( http://www.naxja.org/html/techarticles/uninstall_OEM_ABS.htm ) about there being a lifetime warranty is true? If so, I'd imagine most people would opt for that rather than swapping boosters, etc.

And finally, should I just connect that connector then????

Click to expand...

No rod swap is needed. I took a 97 mc/booster and put it in my 91. We reflared the lines with the proper connectors on it but you can get the adapters at decent parts stores. With the ABS pump disconnected you will lose brakes progressively. and very soon have NONE. Meanwhile of course,no ABS. SOME parts have a lifetime warranty, not all. As others have said, the system is junk and will fail.

IF you reconnect it it may work for a time. Without diagnosing it, tough to say how long it will work if at all.

Just a tip, you may wish to look into replacing your front flex hoses too, ABS pressure is quite high and they can become weak. Upgrade to the longer YJ ones so when you lift it you have enough room!