1993 ST 1100 front ABS pump failure

[tkhelm]

ABS warning light, with the error code indicating front ABS pump failure. Mechanic says the catalog price for a replacement pump is about the same as buying the whole bike of the same year. So it seems there's not much choice but to just keep riding without ABS. With fingers crossed we were hoping that resetting the error code or changing the brake fluid might resolve the issue but no luck.

I haven't seen any listings for this part on eBay (for this model year) or references to front pumps even in this forum (although I see one thread for a rear pump). Can anyone suggest any other alternatives I might have?


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[Upt' North]

Hi dude.
Yes ABS is great until it isn't and will probably kill off millions of vehicles in old age.
You can still get the part but like you say it'll cost a lot, around $1000.00.
Is your bike linked brakes, can't remember for the early ABS 1? I think they are.
You could remove the ABS correctly but will that pass your local inspections? And if linked could be a pain in the Arris!
Make sure if you buy used part you can return it if it's U/S.
Good luck.
Upt'North.

 

[tkhelm]

The catalog price was more than that, at $2300...ugh. Used would be fine but even that's probably pricey enough to be not worth it. Although I really liked having ABS when things have slipped.

I think linked brakes came in with ABS II in 1996 but someone may correct me on that. It's easy enough to turn off the flashing for the ABS warning light so I don't think there's anything to be gained by removing the faulty pump. Just wish I could cross this wire with that wire, recite the proper incantation, and have it working again.


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[mudduc]

I still have the entire braking system, ABS II, from the 1997 ST1100 I parted out hanging on the wall in my garage. It is still a closed system with all the brake fluid included and leak-free. I'd be willing to send it to you for shipping cost if you want to see about making it work on your ST.

Later,
Kent Larson in Minnesota

 

[Sc0tt]

Hi tkhelm

I've recently got my 95 (ABS1) system back up and running. Cost of parts was a whole $0.03 for an o-ring. With these modules, they don't allow for the transfer of fluid from the module during a fluid flush. You end up with 20+ year old fluid that causes corrosion, particularly around the plunger.

Pulling them apart is pretty easy (unless you run into the same issue I did). Just replace the damaged o-rings (if any), clean it all up and reassemble. There is no real procedure listed for re-filling the modules. I did find a very complex write up, but I simply flushed and them filled fluid through the plunger cap, reassembled the plunger, topped up again, and then replaced the plunger cap. The modules themselves appear to have a reservoir so can tolerate some air in the system (as it makes its way to the reservoir). Bleed as normal and you are all good (at least I was).

The only other thing I had to replace was the ABS fuse.

Good luck.

Scott

 

[Slydynbye]

I have a theory, I don't think the pumps get fresh fluid unless they are activated.
After I service the Brake fluid I go out and Stab the brakes to get some fresh stuff into my ABS pumps.

 

[Garry_Coates]

Hi Scott,
I also have a 95 ST with the same problem in Melbourne Australia. Did you do both or just the one indicated by the error code? I am interested in any details you have as the only alternative is to send them to Norm Keller in Canada.
Regards
Garry

Addition: All good -just found reference at: https://www.st-owners.com/forums/showthread.php?162226-1993-ST1100AP-ABS-Modulator-Fault-Code-1-Resolution-Frozen-Plunger-Pump

 

[jfheath]

The system will generate a fault code for the ABS if it cannot go through the cycling process when the ignition is first turned on. There could be a number of issues here:

• one related to the sensor which reads the position of the ABS unit - check wiring (unless the sensor genertaes a different code);
• one related to the wiring for the pump motor - if the wiring has failed, the pump motor cannot cycle, so a fault is reported;
• One is the fuse blowing (same as above);
• one is the amount of fluid in the system. I got a fault once when I pushed the pistons back in, forgetting that I had flushed and bled the system when the pads were half way through their life. Result - reservoir overfull, pump couldn't cycle; fuse blew; fault code. I removed fluid from the reservoir, replaced the fuse, all was well again.
• One due to the ABS modulator dying

Worth checking out the top four possibilities though.

Nb the brakes work perfectly OK if the ABS system is not armed.

All of which is gleaned from personal experience with a 2000 ABS/CBS/TCS model - some of which may not apply to yours. All of which completely exhausts my knowledge of the ABS modulators.

 

[Ron]

There was a guy in western Canada (Chillywacker???) that rebuilt the ABS units. He had a continuous ad on ebay, I think rather cheap I thought.. I don't have an ABS I bike so I never really paid much attention.

 

[Sc0tt]

Hi Garry

Sorry, only just saw your post responding to mine. My bad. I did both in the end. The system only seems to indicate the first failure of this type. You will fix it and then the fuse blows again, this time from the untouched modulator. ie: when the fuse blows due to the front modulator being stuck, it can't test the rear. If your code was only for the rear, then the front "should" be ok.

The fix was stupidly easy in the end. Just had to replace a single o-ring (between the two modulators). The rest was just freeing stuck parts. My biggest issue was that the front modulator was super corroded at the plunger cover. SO much so that you couldn't depress it to remove the circlip. Even when I managed to pull the circlip out (part magic, part luck) it wouldn't release. I ended up drilling a hole and using a slide hammer to remove it. Everything else was easy after that.

Hi Scott,
I also have a 95 ST with the same problem in Melbourne Australia. Did you do both or just the one indicated by the error code? I am interested in any details you have as the only alternative is to send them to Norm Keller in Canada.
Regards
Garry

Addition: All good -just found reference at: https://www.st-owners.com/forums/showthread.php?162226-1993-ST1100AP-ABS-Modulator-Fault-Code-1-Resolution-Frozen-Plunger-Pump