Help! '99 Tahoe doesn't start...

[Osteoblast]

You need:

1. A burnable air/fuel mixture
2. Adequate compression. GM spec at one time was 100+ psi cranking pressure.
3. A spark ACROSS THE PLUG GAP, AT THE RIGHT TIME.

- spark across gap, check. Will check again.

4. Adequately non-restrictive exhaust. When the exhaust is restricted, the engine will often pop or run for a short time, then stall. The exhaust is unlikely to be so plugged that the engine won't even pop.

- seems to be free. Let's assume it's free...

Lots of folks mistake "spark on my spark tester" for "spark across the plug gap". If the plugs are fouled, there's spark...but not across the gap.

- spark plugs new. Spark across gap, yes, will check again.

What does the scan tool show for Cam Offset when cranking?

-tech2 reboots when cranking. Known issue. Obd cable ordered to kill the 12v obd power.
But cam needs 1000rpm to get a correct reading?

It's REAL easy to get the distributor stabbed-in a little off. Any other sensor data looking goofy? Engine coolant temp same as ambient temp when the engine hasn't run for a long time? MAP sensor showing ambient pressure when the key is on but the engine isn't running?

-coolant 6 degrees Celsius
Replaced the distributor. Cylinder one at TDC, distributor set on cylinder 1.
Will do that again and take another distributor which I know works correctly.

EGR valve isn't stuck open?

- how can I check. Will figure that out.

What is your cranking vacuum?

-no tools. Will check that too.

Is the gasoline so old it won't burn? Gas tank empty, but the gauge shows it has fuel?

-added 20l fresh fuel. Will drain some from.servoce port and test light it.
Gauge is freaking around. Getting a code for that.

As said, fuel pressure seems suspicious. How old is the fuel filter?

-fuel filter looks not that old. Don't know.

UPDATE

Checked again the fuel pressure by bridging the pumprelay with connector 30 and 87.
Pump works.
Getting now readings at 62psi. While cranking also 60-62.

I guess it's not the fuel pump as I thought it would be initially.

I get the FC p1345 ckp/cmp correlation. Was gone, but now it's there again.

I appreciate your help.

 

[stutaeng]

That's good fuel pressure...I don't understand why you were getting lower pressure before. Probably should look into an electrical issue? But for now, continue with diagnostics.

Remove the EGR and look at the little pintle to make sure there's no piece of carbon stuck in there...be care when reinstalling it. The gasket likes to slide off and fall where you can't get it. Happened to me once.

Probably worthwhile to check for spark/gap at each spark plug, just to be sure.

 

[Osteoblast]

That's good fuel pressure...I don't understand why you were getting lower pressure before. Probably should look into an electrical issue? But for now, continue with diagnostics.

Remove the EGR and look at the little pintle to make sure there's no piece of carbon stuck in there...be care when reinstalling it. The gasket likes to slide off and fall where you can't get it. Happened to me once.

Probably worthwhile to check for spark/gap at each spark plug, just to be sure.

 

[Osteoblast]

Egr

 

[Osteoblast]

It does move. But lost a screw trying to get it

 

[Schurkey]

- spark plugs new. Spark across gap, yes, will check again.

"New" doesn't mean they can't be fouled. Cranking the engine with fuel spraying but not starting/running can fuel-foul the plugs in fifteen seconds.

But cam needs 1000rpm to get a correct reading?

A true reading should be done at 1000--1200 rpm. But I'm curious what it is at cranking, since the engine won't currently run at the proper checking speed.

-coolant 6 degrees Celsius

Is it 6 degrees Celcius where the truck is parked? The whole point is to coorelate the coolant sensor reading to ambient temp before the engine has run, as a test of the coolant sensor accuracy.

Replaced the distributor. Cylinder one at TDC, distributor set on cylinder 1.
Will do that again and take another distributor which I know works correctly.

The distributor should have molded-in marks for rotor position during installation. Even when using the molded marks, you'd still need to "fine-tune" the distributor position using the cam offset feature on the scan tool.

Procedure is in the service manual.

-no tools. Will check that too.

I'd use a vacuum gauge connected to manifold vacuum. You could just grab a reading of the MAP sensor while cranking...if your scan tool didn't power-down during cranking.

-added 20l fresh fuel. Will drain some from.servoce port and test light it.

Be careful, but yes, that's a good idea.

-fuel filter looks not that old. Don't know.

ONE tank of contaminated fuel is enough to plug a fuel filter.

Consider removing it, and dumping the fuel out the inlet side. If what comes out is full of rust and debris, replace the filter.

UPDATE

Checked again the fuel pressure by bridging the pumprelay with connector 30 and 87.
Pump works.
Getting now readings at 62psi. While cranking also 60-62.

I guess it's not the fuel pump as I thought it would be initially.

Test your fuel pump voltage WITH THE PUMP RUNNING, as close to the fuel pump as practical--generally at the rearmost harness connector before the wiring disappears on the top of the tank.

Suspicion: Low voltage with the relay in place, adequate voltage when the relay is removed and jumpered. Potential defective relay, or poor connection between relay terminals and relay connectors in the relay socket.

I get the FC p1345 ckp/cmp correlation. Was gone, but now it's there again.

As said, verify the rotor position vs. the molded numbers on the distributor, see service manual for details. Once the engine runs, you can adjust distributor position for proper cam offset.

 

[Osteoblast]

Thanks. Will work with that.

Recovered the screw. Egr back in place

Fuel burns good.

 

[Osteoblast]

Would like to upload a video. But I don't get it to upload here.

 

[Erik the Awful]

You can put the video on YouTube and put a link to it here.

 

[stutaeng]

I had a 4.3 that had everything seemingly okay such as spark, fuel pressure, etc., and it wouldn't fire ONLY when it was damp in the morning. I thought I had fixed the problem once by changing spark plugs, but problem came back a few months later.

At some point I upgraded to a battery from the V8 trucks. Towards the end (engine had low oil pressure so I replaced it) I was able to start the truck after literally cracking nonstop to a good minute or more. I never figured out the problem, but suspected moisture in the distributor caused a failure to start, then possibly flooding the engine. I think extended cranking (gas pedal pressed all the way in) helps clear out a flooded engine. Maybe try that.