So I did some re-testing to confirm and need to make some corrections;

With key in the on position I get no measurable volts at the pump power supply connector by probing red & black wires on connector alone or when the meter is connected to the neg battery post.

With truck running I get 14 V when probing the connector and, for good measure when the black meter wire is on the battery post.

I repeated the same tests on the vacuum solenoid switch and got the same results, power to switch when running but not in key on only position.

Both circuits go dark after about 30 seconds presumably based on the O2 sensor feedback.

Measured continuity in both as 1.2 Ohms (1.1-1.2 w/ meter set to 200 position). *The meter measures about 0.4 when the two needle probes are touched together.

Just for clarities sake this is the vacuum solenoid (getting vacuum from manifold and passes it to the pump valve), fuse/relay block (conveniently )tucked along side of battery, the pump intake hose (this is apparently a after install of the relocation kit) and the pump itself. Looks like the radiator let go at some point.

 

Sounds like the power and ground for the pump are good. Depending oh how complete you want to make your testing, you could try to power the motor with fused power to see what happens but it looks like the motor may be bad.


George

 

Thanks for walking me through. I came to that conclusion too but wanted to hear what you thought. Not sure why there's no power unless the truck is actually running. On the schematic it says hot in run/start which I also read as the "on" position but maybe it really mean running? Joe
PS I had already ordered the pump based on the bench testing I did, Should have it in over the weekend.

 

Yes power is supplied as always on to the relay contacts and on in run to the +V side of the relay coil but the relay contact power is not routed to the pump motor until the VCM grounds the other side of the relay coil and this only happens after the vehicle is started and then for a specified period as the truck warms up, probably until the fuel system goes closed loop. The pump supplies air into the exhaust stream to help burn unburned hydrocarbons from the rich mixture of a cold engine. This is how it reduces emissions.


George

 

Following through on the 4x4 side. The firewall solenoid was testing bad because it was letting vacuum through to the 4x4 diaphragm under the battery even when there was no call. All other components of the vacuum system checked out..

Replaced the solenoid and lucky for me the system is functioning. Ran it through all settings and the only hiccup was a decent clang going into 4Low but once it finished doing its thing it was most definitely in Low. Ran through everything twice and feels good. Came out of 4x4 into 2WD and no binding on turns so the solenoid vented correctly.

Now I should probably check fluid levels in the transfer case.

With the old solenoid in my hand I could apply vacuum and feel it sucking through the other port so was not working. I gave it a few smacks on the bench and it kinda sealed up, might of even worked again so that might be a field check and fix if you're in a jam.

 

The AIR pump went in this am and all seems to be working. Pump stayed on for close a minute on a full cold startup and maybe 30 sec when warm. Crossed fingers that it stays fixed.

 

Glad your fixed.

George

 

Note I have corrected post #6. Upon closer inspection I found mine was plumbed exactly same as diagram in post #2.