A quick way to test the pump on the bench would be to apply battery voltage to pins 3 and 2 while holding the your thumb over the output air port. If the motor quits running after 3 seconds your pump is probably good. If I'm not being too nosy, where did you order the pump from and what was the cost. My pump may need to be replaced too.

 

I tested it on the bench. Actuator went up and down. Pumped very slowly, and kept pumping. Never put out much air. https://www.ebay.com/itm/Actuator-Pu...72.m2749.l2649

 

It's not a very strong pump and it will pump forever (on the bench) if the pressure port is not blocked off. If the port is blocked and it continues to run then the pump is not producing enough pressure to activate the pressure switch or the pressure switch is defective. In either case the pump assembly is bad and needs to be replaced.

 

I installed the new pump. 4wd works as it should now.

 

Is there a chance you could run a test for me? The motor should run for about 3 seconds to pressurize the line. I'd like to know how long your 4WD holds that pressure before the pumps kicks back on. I've read that is should be around 3 minutes on a system with no leaks. Mine is only holding pressure for about 3 seconds. What is yours doing?

 

I pulled the 4WD air pump out of my Tracker, plugged the output air line with a pressure gauge
and jumpered power and ground back to the car.





I only jumpered the red and black wires. The pink wire is not connected.





This is the instrument cluster in 2WD, engine running.





I put the lever in 4WD and the pump shut off when the pressure reached 6 psi.





As soon as the pump motor started the 4WD drive light came on. After I reconnected the pink wire the 4WD light
came on AFTER the motor stopped running (proper operation).

 

Summit racing has these pumps for $160 but you will have to use the connector from your old pump.
https://www.summitracing.com/parts/m...SABEgKhwvD_BwE

 

I tested my pump on the bench with a battery and a fuel pressure gauge. It would not hold
pressure. I sent it off to Troy at Refurbished 4x4 Actuator Air Pump Repair for a rebuild. He
only charges $132 and I didn't have to splice my connector onto a new pump.




The 4WD indicator stayed ON the whole time the pump was removed from the car. When I
jumpered a dummy load (a 12 volt Harbor Freight test light) across pins 2 and 3 the 4WD
indicator went ON and OFF with the 4WD lever operation. The computer senses the open
pink wire as "system pressurized" signal.




I reran the pressure test after the pump came back from repair.





The pump sat on the bench for an hour with no measurable drop in pressure, so in my case
a rebuild was a viable alternative to replacement.