I have 91.5 running gear sitting under an 85 crew. I swapped entire breaking system. Only things different are 1 brake line, 1 Extention from Rwal to axle, and a lengthening of wiring harness (soldered in 18 extra inches in the middle of the harness. I have a firm peddle with truck off, truck on however, I have dash warning lights and a peddle that loses preasure. I have run the fault diagnosis and am reading code 3-Open dump valve wiring or bad control module I checked all connections at the rear of truck. I want to try and keep the ABS before I break down and ditch it for a different proportioning valve. How should I proceed?

 

Also, disabling the ABS module doesn't help. On and they are well bled, I even had the brake shop do it. I just didn't let them start diagnosing at 50 an hour.

 

It is probably the dump valve. Temporarily bypass it to confirm, or plug / cap the rear brake lines before and after the dump to test.

JP.

 

With all the problems guys seem to have with this early ABS system, I don't understand why you would want to use it? My 84 Crew, with it's original braking system, works great...If I need ABS then I will pump the pedal manually and have the same basic effect.

 

I`m going to say dump valve also, same symptoms as I had a couple of months back. I bypassed mine and now a super firm pedal and almost too much rear brake, but I also have 3in shoes and 1 1/16 wheel cyls. I plan on fixing it proper...someday.

 

I say fix it. Nothing sucks more than having your rears lock up in bad weather because the ABS isn't working right.... ask me how I know...

 

Thrashingcows, I here ya. I might ditch the system yet. However, I still want to try and make it work. It worked when I pulled it apart, so it should work again. Could the extra length of wire goof with the reading from the sensor?

 

tHISS, GOOD question, my 91 d350 has always had the brk.&abs lites on but it has a 38 in. ext., added to the cab ,,,,so what y'll think does the extra length of wiring have a effect on true fuction???? JIM, WANA,WHAT 'YA THINK.

 

Bump

 

Sorry for the shameless bump earlier in the week. I have been doing so searing and found that a 10 amp fuse was stuck where a 20 belonged (we were goofin with the fuse block the night we were ready to fire and blew quite a few headlight fuses) and that the front prop valve had the wire loose. Took car of these issue and reset the RWAL and lights went out, until I stepped on the pedel. Good pedal initially, then stomped on it and pedal could be pushed to floor and lights back on. Now when I unplug the RWAL I have similar brake feel. While driving the breaks work good at low speeds and initially, but I doubt they will work good on a panic stop. I am going to be stubborn and keep trying to keep the abs system. Mostly because, I don't want to re-bleed the system, oh I checked the master reservoir and it is still full.

 

I know what you mean mine does it in the rain but when the truck gets warm and ideas why??? Thanks