Hot Rod Forum banner
1 - 15 of 15 Posts

·
Registered
Joined
·
747 Posts
Discussion Starter · #1 ·
Hi all, as many of you know I had all sorts of problems with my 4-wheel disk brake conversion. The primary problem was a defective master cylinder. I also installed a vacuum pump which really made the brakes even better.

My 8" dual diaphragm booster requires 18" of vacuum. My pump running all the time pulls 25".

What is the best option to control the pump?

#1 put it on a relay and let it run all the time?

#2 use a vacuum switch to control the pump?

#3 use the brake light switch to control the pump?

Thanks!
 

·
Registered
Joined
·
747 Posts
Discussion Starter · #8 ·
Hey all. Brakes are working great but I'm having a hard time controlling the vac pump run time.

I have a Jegs vacuum control module that's supposed to be calibrated for 18-22" shut off but my pump runs continuously until I'm pulling 25" and even then it short cycles on to off.

I fear I'm going to cook the pump. Have another module coming Sunday to see if it actually works properly.

Also 49 Ford is using his 1/8" pump port for manifold vacuum. Is this correct it looks an exhaust port to me.

Thanks to all.
Bicycle handlebar Motor vehicle Automotive tire Bicycle tire Bicycle part
 

·
Registered
Joined
·
747 Posts
Discussion Starter · #12 · (Edited)
Okay just to update...the new vacuum switch from Jegs came today. I installed it and I still have the same problem. The pump runs and at 25" vacuum it will shut down and then immediately starts again. The swtich in normally closed so vacuum, breaks the curciit and the relay then drops out. The switch is suppose to shut off at 18"-22". I read somewhere that the switches have an adjustment screw and this one does have a screw. I tried several different adjustments and could only get the pump to shut off at 22" but it still short cycles.

I used avacuum gauge to check for vacuum leaks and found nothing major. The system leaks down about 1-pound in 30-minutes. I wouldn't think that would be a big enough leak to cause short cylcling. Could the relay be casuing the problem????

Thanks!!!!!
 

·
1949 Ford Coupe RESURRECTION
Joined
·
1,047 Posts
Did you take a look at my website on this subject? And is your vacuum gauge out of calibration? And do you have a canister and correct check valve(s) in place? No offense, but you are missing something. Relay probably isn't the issue..
 

·
Registered
Joined
·
747 Posts
Discussion Starter · #14 ·
Yes , I looked at your site. I have check valves but my snap on vacuum pump and gauge is very old. I actually think I'm loosing vacuum through it when I do the leak down test. You can see in the picture I posted earlier the sensor I used is diferent than yours. If you remove the sensor from the base fitting there's a small screw on the under side to calibrate the switch. So if my gauge is reading incorrectly I really may be in the range shut down range of 18"-22" . I just need to figure out why it won't shut down and stay off for awhile. It will run about 20 seconds then stop and immediately start up for another 20 seconds or so.
 

·
Registered
Joined
·
747 Posts
Discussion Starter · #15 ·
Hello- I talked to Jegs tech guy today. He said it could be the relay. So I picked up a relay at Autozone today. I installed it and the pump stops and doesn't start again until I hit the brake pedal. HOWEVER- the relay doesn't hold and comtunely clicks trying to retart the pump. I tried this with two different vacuum sensors and have the same problem. I think the original relay I bought from Jegs is just a defective relay and the one I bought at Autozone is just cheap and poorly made China junk. I'm going to the electric supply house tomorrow and buying a heavy duty american relay .

I will keep you posted and thanks.
 
1 - 15 of 15 Posts
Top