96 Tahoe dies while driving and won't start

[east302]

Just to confirm, you said that you have spark at all eight cylinders, right?

Your fuel pressure is within spec (60-66 psi) and since it doesn't drop within a few minutes, your regulator and injectors should be good.

Have you done a compression test?

Do you have a scanner that can read the output from the engine coolant temperature sensor and throttle position sensor? Try holding the gas to the floor when cranking, see if it starts. That would probably indicate a bad ECT sensor.

You can test the ignition feed circuit to each injector and see if you're getting power to the main harness. Disconnect the harness at the intake and with the ignition on, see if you get voltage at each ignition feed circuit. It would be the pink wires, circuit 439:





If you have no voltage, look for a wiring issue between the fuse block and the harness.

Edit: could be a stuck open EGR valve, but I'm not sure how to test it.


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[Nightflyer]

I've spark on everthy cylinder, fuel presssure, etc..is okay.

My OBD-Software can read the ECT and TPS data...everything is fine.

I've never done a compression test...i think it's not necessary. The car runs fine and dies wirhout any signs of no compression or something else. The timing chain is okay.
Tomorrow i'll check the harness of the injectors.

The car is not starting while holding gas on the floor...i've tested it..

What is, when i have no power to the injectors?

 

[east302]

If you have no voltage to the injector(s) then look for a damaged wire between the harness and fuse block.

I would suggest looking at a stuck open EGR valve, but those should, in theory, throw a code when the pintle isn't cooperating. I know you can test it with a scanner, commanding the pintle position to certain points, but I believe that requires a running engine.

GM does have a procedure for testing individual injector solenoid operation and poppet pressure drop/flow, but the test equipment would probably cost you more than a new spider assembly.

What voltage are you getting for the closed TP sensor? It should be below 1.25V.

What temperature is the ECT reporting...close to ambient and not some oddball number?

The wet plugs does sound like leaking injectors, though.


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[Nightflyer]

So,

It's all tested:

- there is 12V on each injector
- 0.78V at the TPS
- the EGR looks pretty good (seems to be new)
- teh ECT reports the correct temperature

Not all plugs are wet...only two of them. The other six are dry....

 

[bigfootchiro]

Here is the link....

http://www.rockauto.com/de/catalog/...5.7l+v8,1061356,fuel+&+air,fuel+injector,6224

In the ite description is 5mm and 6.5mm listed

The 6.5mm are the new MPFI design and the 5mm is the old CPFI, which you do not want. Click on the pictures and you will see that the 6.5mm is controlled at the injector. BTW, do not buy them individually. If you do buy it, buy the entire assembly.

And btw, @east302 is the man when it comes to this stuff! Glad he chimed in. He helped me a few times already through some issues with my truck. Thanks @east302 for helping people out on these forums!

 

[east302]

So,

It's all tested:

- there is 12V on each injector
- 0.78V at the TPS
- the EGR looks pretty good (seems to be new)
- teh ECT reports the correct temperature

Not all plugs are wet...only two of them. The other six are dry....

Does your scanner have history data for cylinder misfires?

Well, you've got fuel (or too much, which cylinders were flooded?), spark and air.

The next step, since you have power to the injector harness, would be to see if the computer is grounding each injector during cranking. A noid light would normally be used to see if it flashes during cranking, but you may have to rig something up to fit the spacing between the voltage supply and VCM circuit terminals in the main harness.

Or, you could put a test light to battery positive and probe the ground (or test light across the two terminals) to each injector during cranking and see if the light flashes.


I haven't done it, but I've read where you can check to see if each injector is spraying by disconnecting the coil and coil module, removing the upper intake, reconnecting the injector harness and then pulling each injector one by one to see if it sprays while cranking. Careful, it's fuel so use a towel or something. Also, those stupid plastic squeeze clips on the injectors can break.


It sounds like intermittently sticking poppets flooding out some of the cylinders. There is a GM procedure for cleaning them, but it requires the truck to be running.

If I was going to throw a part at it, it would be a new MPFI assembly. I did this on my 98 truck, and it was a noticeable improvement over my 98 Tahoe.




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[Nightflyer]

Hi east302,

Cylinder 1 and 4 are wet..the other are dry.

The history shows nothing about misfiring....everything else, but not this.

But i remember one thing: I've changed the spark plugs 3 or 4 months ago...and it looks like they are running with poor gas (not rich enough...sorry, my english is not so good.....) and sometimes when i start the tahoe it seems like, that not enough gas is coming to all cylinders. The chevy starts very slow. I hope you could understand what i mean....

Nathan & east302: thank you for your help. When it works and my chevy is fixed and runs very well, i'll send you some beer from Bamberg/Bavaria....

THANK YOU SO MUCH.....!!!!

Matthias

 

[east302]

Well, hope you get it figured out. Let us know if the new injectors solve the problem.

Your English, by the way, is arguably better than many Americans.


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[bigfootchiro]

Well, hope you get it figured out. Let us know if the new injectors solve the problem.

Your English, by the way, is arguably better than many Americans.


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Bahaha, right?! If only some Americans would try as hard as you @Nightflyer to speak proper English! I hear the beer is very good over there in Germany. I need to have a vacation over there!

 

[east302]

Yeah, I wouldn't mind seeing Germany one day. I had some German beer at DisneyWorld that was really good...I think it had (of all things) grapefruit in it.

Germans would probably think it wasn't a "real" beer though, lol.


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