Fuel pump, crank no start

Check the 15-amp fuel pump fuse first. If it's okay, a quick check is to swap the fuel pump relay with one of the other ones like it. If you still don't hear the fuel pump run for two seconds when you turn on the ignition switch, we'll have to make some voltage tests in that circuit. The best tool for that is a test light. If you don't have one, you can find a perfectly good one at Harbor Freight Tools, any hardware store, or any auto parts store.

Here's a link to an article on how to use it, if you need it:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Fuses check out okay. I did swap the relay for the wiper relay same number. weird thing is i left wiper relay out but wiper still worked. Also i notice before i put new pump in was my gas gauge didn't work when key in on position.

Like to add that today i jump the relay and fuel pump came on and fuel entered the line but still no start. But nothing at all with relay in and swapped out with same relay.

On most car models you should hear the fuel pump run for one second when you turn on the ignition switch, then it turns on again during engine rotation, (cranking or running). I might have sent you down the wrong path by your observation the fuel pump is dead for that initial one second. I should have had you check for spark first. Most crank / no-starts involve a loss of fuel pump, injector pulses, and spark, all at the same time.

Find an injector that you can back-probe through the connector next to the wires. Use the wire that is the same color at all of them. You should find 12 volts there, but I can't tell if that is all the time the ignition switch is on or if it's for just that one second. If you let me know, I'll add a notation to the diagram I posted earlier.

There must be 12 volts at the injectors when you're cranking the engine. If there is not, we need to look at the main relay circuit, and the fuel pump relay is just a part of that circuit.

I will do that and post back what i find. Thanks

Do i need to remove the intake to get to injectors? I'm pretty sure it's not getting spark.

Yes, intake has to come off to replace the injectors, but I was hoping you could reach the connector on any one of them to take the voltage reading without doing that. If you must remove the plenum to do the voltage test, I'll try to figure out an easier way to do that.

I apologize that I didn't make these easier to read. Step 4 at the very top of the second drawing says to remove the intake plenum.

I was really hoping i didn't have to do that. Seems like that's when i start breaking s*** when i take things apart that i'm not familiar with, but i got to get this car fixed. Ugh. It's not firing so assuming that much what else can i look at . crankshaft sensor was replaced 5 years ago. Could that gone out again?

I really appreciate you taking the time to help walk me through this. Everyday i been trying something in between 2 jobs.

Here's a different way to test this circuit. Look for "Engine Controls 3" fuse. It looks like that will be a red 10-amp fuse with two small holes on top for test points. This is actually a better place to test because while it is in the same circuit as the injectors, testing right at the injectors doesn't include this fuse in the test.

Turn the ignition switch to "run", then check the voltage on both of the test points on this fuse. If you see 12 volts on both of them, the fuse is good. If you find 12 volts on just one of them, the fuse is blown. If you find 0 volts on both test points, check again while a helper is cranking the engine. If you never see 12 volts there, swap the main relay with another one like it.

Well i got 0v on both while cranking, but don't have another relay to swap out that i saw. How can i test the (3412 main) relay?
Let me add that on one side of fuse the test light was really really dim i almost didn't see that it was on.

Where do i go from here? Just to update problem i have a crank no start. New fuel pump crankshaft position sensor was put in 2013, no fuel in line (pump not running 2 seconds but does when i jumper relay ) and no 12 volts at ec3 fuse both sides. I might have to send to shop because calling junkyards and can't find parts. Ugh. I know it has got to be something simple but I do not know. 98,000 miles was great running car.

We're making progress. Even if the test light was dim on one test point on a fuse, it has to be the same on the other test point if that fuse is good.

Since the fuel pump runs when you bypass the fuel pump relay, we know 12 volts is getting that far, therefore, it should also be on terminals T1 and T2 on the main relay. Pop that relay out and double check there's 12 volts on two terminals in that socket. Those are the two blue arrows in the diagram. In the rare event it is missing, there's a break inside the fuse box.

Assuming you do have 12 volts on two terminals for the main relay, either that relay is defective or it isn't being turned on. The main relay goes by other names on other car brands, but they all get turned in by the Engine Computer. The computer does that when it sees signal pulses coming from the crankshaft position sensor and the camshaft position sensor, meaning the engine has to be rotating, (cranking or running). No reference is made to any sensors for your main relay. I suspect the computer turns the fuel pump relay on separately, but in this case it can't because the problem lies before that.

If you look at these charts, we're down to step 4 already. They include a lot of little steps in between the big ones, so it looks more involved than it really is. If you have the 12 volts on the two terminals in the main relay's socket, try a different relay or jump terminals T1, (blue arrow), to R2, (orange arrow), then see if the engine starts. We know one of the terminals to use. That's either one that lights up with the test light. I can't find a drawing that shows the individual terminals and their designations. Look on the bottom or on the side of the main relay to see if they have the designations shown. They're usually printed on the side on import cars and molded on the bottom for domestic cars. One of the two where the test light didn't light up has to be R2.

Thanks, I'll try that when I go home for lunch. I really appreciate it. also I got a hold of a scanner tool if that will help pull codes and give you some more information.

Why does it have to be -6 degrees out?. Brrrrrr

I went back to test that ec3 fuse that was dim and got nothing with key on or cranking but fuse is good.

I went back to test that ec3 fuse that was dim and got nothing with key on or cranking but fuse is good

Either the relay is defective or the Engine Computer isn't turning it on.

Use the scanner to see if there's any diagnostic fault codes in the Engine Computer or in the Body Computer. These charts cover the crank / no-start diagnostic procedure for use with a scanner.

Before you start this, there's one more thing regarding the main relay. If that is a gray, 1"-square relay with four really skinny terminals, (two are a little further away from the edge than the other two), their mating terminals in the fuse box are known for becoming spread, then they don't make good contact with those on the relay. Often the relay will work while you hold sideways pressure on it. If you find that, there is usually enough room to go in beside each one with a small pick to squeeze them tighter.

Well here's the codes and whatever they mean. Not familiar with scanner but figured out how to do this part....
U2105, u2107, u2105, p2176, p0261, p0264, p0267, p0270, p0037, p0057, p0646, p0458, p05600.

And thanks a lot, I appreciate all the help you're doing . All else fails I'll just break down and take it to the shop pay that expensive bill that don't want to pay, but i need car running for my job instead of driving my Avalanche. The difference in gas mileage is crazy I'm losing money daily.

What tested the three fuses related do the ECM using test light hooked to positive and all 3 fuses lit up so is the ECM grounding out somewhere or shorted?

P0037 HO2S12 Heater Control Circuit Low Voltage
P0057 HO2S Heater Control Circuit Low (Bank 2 Sensor 2)
P0261 - Cylinder 1 Injector Circuit Low
P0264 - Cylinder 2 Injector Circuit Low
P0267 - Cylinder 3 Injector Circuit Low
P0270 - Cylinder 4 Injector Circuit Low
P0458 - Evaporative Emission Purge Solenoid Control Circuit Open
P0646 - A/C Clutch Relay Control Circuit Low
P2176 Throttle Actuator Control System - Idle Position Not Learned
U2105 - Loss communication with ECM
U2107 - Lost Communications with Body Control System (BCM)

The first nine fault codes shouldn't prevent the engine from starting. Most of them likely set due to the underlying problem, and will not need any attention.

The "Lost communications" fault codes point to a failed Body Computer, but there's two things to try first. Check the three fuses with the blue arrows pointing to them. If they're all okay, disconnect the negative battery cable for a few minutes. Even better, when it's disconnected, touch the negative cable to the positive one to insure all the computers' memory circuits are fully-discharged. Reconnect the cable, then see if the engine starts.

I will try as soon as i get home. Thanks again

No luck. Did you see where i said all 3 engine control fuses are testing positive for ground with test light?

Sorry about 3 pics. The last one is the one i wanted to show hose 3 fuses yest negative ground.

Body control mod is one behind glove box i think. I going to pull it out and look at inside it. Or not right now. Its freezing cold out. Lol

I'm thinking unplug the BCM and test those fuses again for ground short and see if its gone.

What you thinking??

How did you perform those tests? To check for a ground, the test light's clip has to be on the battery's positive post, then the light will light up when you probe a point that is grounded. I suspect you found places that will check to ground. We know there aren't going to be three separate problems develop all at the same time. Also, if there was something shorted on one of those circuits, that fuse would have blown.

I put test light on positive and check the fuses and all 3 light came on. Only those 3. I just had a hunch that T least one was going to light up but all 3 did. Light came on then slowly dimmed but remained on.

And fuses are all good throughout the system.

What you're doing is powering up those circuits with the current that is flowing through the test light. The light dims once the capacitors in the driver circuits inside the various computers charge up. You're seeing the same current surges that often cause fuses to blow for "no reason" when the disconnected battery is reconnected.

Okay, I see. Makes sense.

So what's next step?

Everything points to a failed Body Computer.

First I'd disconnect the negative battery cable to see if the Body Computer has locked up. We jump to defective computers too quickly and blame them for everything, but there was such a case in the early 1990's, and GM did have a lot of Engine Computer problems in the late 1980's to mid 1990's. Disconnecting the battery did temporarily solve a lot of those problems, which is why we became accustomed to doing that. It's less of a problem today, but it's something simple we don't want to overlook.

I did that with the last step when you told me to disconnect the negative cable and then touch the positive to drain the memory for the computer.

Another week down. What to do next?

Could my key be bad?

Crankshaft sensor?

Body Computer.

The alternative is to use a scanner to look at what the computers are seeing and responding to. That will let you command the computers to do things such as turn relays on and off. That will show if they can control them.

Okay, so this is what your thinking?

Shame on me. I thought I posted the location already. Sorry, but it appears I did not.

It's listed as "behind the upper right side of the instrument panel".