While thinking about how this is supposed to function I'm gonna say the check valve is meant to avoid back flow to the manifold from the reservoir and other lines at times when those components are at higher vacuum than the source. If the reservoir is at max vacuum of say 20 in/Hg but manifold vac is low that would scavenge from the system. Guess it might not affect engine performance much but maybe could cause weird symptoms in the HVAC and 4x4(?).

 

I believe I have correctly diagnosed the secondary air system (AIR) and got the vacuum correctly routed to the AIR solenoid vacuum switch. On startup I hear the exhaust burbling down by the pump as the system is now opening the vacuum valve by the pump and pulling in (not blowing out ) air into the exhaust through the non-functional pump. I bench checked the pump to the best of my ability and believe it is shot.

Trying to figure out if I'm testing for power to pump correctly and if the relay is working. Since I have no training in this and I'm not very good at it, looking at the circuit provide by swartlkk I have a couple questions:

1)Does truck need to be running or is ign in "on" good enough for testing?
2)Can I test for power to the pump by simply hooking leads to the connector with the ign in the on position or should the neg of the multi-meter be connected to the neg post on the battery?
3)Does the relay send power to the pump or "complete" the circuit? I get power (12-14V) to the hot side of the pump connector when the other lead is connected to neg post of battery but nothing (very small) reading on the multi-meter when I probe both sides of the pump power connector. Calling @GeorgeLG !

 

Ignition on, does not need to be running for electrical tests. Vacuum of course is another story.

The relay does two things. It routes +V power to the pump motor and +V power to the solenoid/relay internal to the assembly to energize the pump motor.so +V needs to show up at both C2 A and C1 A for the pump motor to energize. You test for this with the positive lead of your meter on those two points one at a time and the negative lead of your meter on battery negative once with the connector attached and again with the connector removed (4 measurements). The reason why you do these twice is to see if proper power can still be delivered when the motor is loading the circuit. In addition to that the ground side of both functions at C1 B and C2 B must be sound to complete the circuit back to the battery. There are a couple of ways to test the 2 grounds:

One is to move the meter negative lead from the battery ground to C1 B and C2 B with everything connected and see if you get the same readings as before. If not, tell me what you get and we go further to figure out what is wrong with the grounds.

George

 

Thanks George and I did read the write up you have here as asked in my AC thread . So I would be probing the relay block at position 87 and 85? Also if I connect pump I figure I will blow the 30 amp maxifuse which is how it was when I got the truck. Right now the motor is disconnected.

 

I need to be more clear on what we are diagnosing. So when you got the truck, the Air Fuse, 30A was blown? Are you trying to figure out why that is? If that is the case then the problem is almost certainly the motor itself. We can test the circuit getting power and ground to the motor and we can test the disconnected motor with a fused test wire.


George

 

Yes 30 amp fuse was blown when I got the truck. I agree that it is likely that the pump took out the fuse. I was/am trying to diagnose if the relay is sending power to the pump or if the power that I am seeing on the hot pin of the pump power connector is always present and it takes a functional relay to complete the circuit.

To reiterate, using a multi meter I get 12V to the hot pin of the pump connector when the neg of the multi meter is connected to the neg battery post. I get no reading when the meter is connected to both pins of the pump connector. So I was trying to figure out if there could be a relay problem.

In other words, why don't I get a reading when probing both pins of the pumps power connector with the multi meter?

 

The fact that you get +12V on any connector indicates that the relay is working. The ability of the circuit to maintain minimum voltage under the motor load is another story and can be tested later. There are 4 wires at the connector for the motor and its solenoid. Which two are you measuring with your meter after you pull the negative meter lead off of the battery negative terminal(C2A/red, C1A/pnk-blk, C2 B/blk, C1 B/blk)?

George

 

Well I'll take that as a positive.

But now I'm a little confused and I want to answer your question correctly. I wish I could check right now but to be clear, the plug connector to the motor only has two wires leading to it and unless my eyes are that bad, it has only two male pins (are you counting the wires to vacuum solenoid as well?).

I don't remember the colors of the wires off hand and didn't have the diagram in front of me at the time but one led me to believe it was the most likely hot. I used an alligator clip on it and another to the battery and voila, 12V. When using clips on both pins I get nothing. Looking at the diagram I would say it was red and pnk/blk but I'm not home to verify.

 

OK, lets start with the two pin connector for the motor. That should be red and black wires. Motor disconnected, positive meter probe on red, negative meter probe on the battery negative post and you get +12V, correct? If so then the relay works but we don't yet know how the circuit performs under a load, but that's for later Moving the meter negative probe from the battery negative terminal to the two pin motor connector and the black wire should also give you +12V. If no reading then there is a problem with the ground that we need to find and because the power wire and ground wire travel in the same harness branch for a while you may be blowing fuses because of a wiring fault (corrosion, breaks, short to ground, short to power, etc). If I have that right then the next test is motor disconnected, resistance from the two pin motor connector black wire to battery negative post meter on lowest ohm range. Should be continuity with less than a few ohms reading. If not then inspect that black wire from the motor connector to the frame grounding point


George

 

Correct. Makes sense, I will check for continuity in at the pump plug connector and get back with the result. Thx!