Introduction
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Part 2. In this video i give an example of one way i go about trouble shooting a no start issue when i have limited resources. on a 95 Chevy Tahoe
We will be looking at the oil pressure switch side of the circuit This isn't how I usually go about it however I wanted to give an example of what you can do with just the basic tools and schematics to trouble shoot a no start issue hope you enjoy
Content
Hey guys, we'll round some hair from Robinson's out of tolls of time, calm welcome back today, we're going to revisit the Chevy Tahoe 5.7, with the relay issue.
Trucks been running great, however, like I mentioned at the end of the last video I would like to go back and revisit that oil pressure switch to make sure it's working correctly before I return it back to service.
So, let's get in there and see we got first I'm gonna do is fire it up, I'm plugging relay and seem stage running you see it drop dead.
Your fuel pump kicked on right away, just timed out.
Alright, let's see, what's going on, let's take a minute and review this wiring schematic one more time before we move ahead to much further.
As you can see, this is the fuel pump oil pressure switch.
It shares the same power source as the fuel pump relay.
That goes up to that main fuse, which we know is good because we check that in the previous video.
So if everything work working correctly, it would switch over and go to this gray conductor, which would go straight down to the fuel pump and allow it to run as long as there is oil pressure, even if the fuel pump relay fails.
So this tan wire goes up to your oil pressure gauge.
Okay, so the next thing I would do is make sure I have the correct control voltage and everything going to the pressure switch.
So you want to unplug it as you see, I have it unplugged I have to air clean, remove to get me better access and I got the pressure switch and remember by looking at the wire schematic.
It should be this orange wire.
As you can see, we have control voltage.
So let me see if the fuel pump kicks on when I install the jumper so go back to his commander, and you can see it's the orange and a gray wire the brown ones for your your pressure, gage.
Let's take install a jumper and see the pumpkins on yep fuel pump kicked on okay.
So that's telling me that that oil pressure, slides fuel pump switch isn't working correctly.
So what I'm going to do, I'm going to go pick up a new one, I'll come back and we're going to bench test that new one to see how it operates and we'll take it from there.
Okay, guys I, just got back from the forest or I got the new pressure switch and now I'm going to show you how to do a simple bench test.
So I can show you how it operates and plus I'll be making sure to switch works correctly before I install it onto the vehicle.
So what I'm going to do after looking at the wire diagram and inspect and wiring on the vehicle, I determine it's the two outer terminals that are connected to the contacts on the inside of the switch that are going to close somewhere between three to seven psi, give or take.
So what I'm going to do to be performing this test? As you can see, I got an air regulator, I'll be taking this pressure, switch screw it into the air regulator hook and compressed air up to this side of the regulator.
This regulator could go anywhere from zero psi from nothing up to a hundred, but like I mentioned, we only have to go up to ten at the most.
So the next step before I go hooking compressed air.
Up to that, so I got my multimeter I'll, be setting this to continuity.
Okay, so when it contacts closed, the circuit will become continuous will be a continuous loop.
Therefore, two contacts will close.
The current will flow from one terminal to the other and you'll hear that audible signal on my multimeter.
So let's go ahead and perform this test.
Hopefully you can see what I got here.
I got the compressed air hooked up to the regulator right now.
It's turned all the way down.
It's back going down to zero psi.
I got my alligator clips hooked onto the pressure switch I, take and hook up my multimeter.
It set up the continuity.
So what this is going to act, like is oil pressure, except for I'm, going to be using air pressure, so by the time that it's hard to read this gauge, because it's a zero to 160 psi.
However, the first line represents somewhere around five psi.
So by the time it hits that first line I'm, saying those contacts should close and you'll hear the audible signal on the multimeter.
Let's give it a shot.
Okay gauge is just starting to come off the pin, not quite five.
As you see right, there was about four psi and the contacts closed.
So this switch is working correctly, every time right around 3 to 4 psi.
It's kicking in closing the contacts who's coming down right behind the distributor, and you can see that's where the oil pressure switch is located.
Okay, guys, I'm back over at the bench, I got the old pressure switch removed from the vehicle it wasn't too bad to remove.
It does require a special socket.
However, if you have an inch and 1/8 open end wrench, you can reach down there and break it loose or a pair of channellocks or some means of grabbing a holder.
That's not breaking it loose and then you can reach down and simply unscrew by hand.
It's an NPT, it's a pipe thread.
So it's a tapered style thread.
So once you break it loose it'll get easier as it goes.
So, let's test this one and see what we got: okay, I hooked up to the two outer terminals, just like before I'm still the meter that set on continuity.
So let's see what we got: okay, I'm just starting to lead to, pin okay, mi5, there's time, there's 20 and, as you can see, the contacts still haven't closed or if they did closed, you're shot.
So this, which definitely is faulty so let's go and I install the new switch and see what happens before installing the new switch you're going to apply some thread compound onto the threads.
The last thing you need is it to leak and create another issue after you fix one.
So that's installed.
Okay, as you can see, I've got the new switch installed.
The harness is plugged back in.
Let's do a couple checks: okay, I got everything buttoned up after reinstalling the switch as you see the air cleaners back on it, I feeling pretty confident about the repair, since we bench test everything so I'm going to reinstall the relay and see what fires up so now, I feel much more comfortable about returning this one back to the customer to get all our troubleshooting check, the entire circuit everything's back up to snuff.
So you should be good to go all right, guys, I, hope you found this video helpful.
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I will run simple, Ronson's Auto tools in time that calm thanks for watching stay tuned.
