96 Tahoe dies while driving and won't start

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

east302

I'm Awesome
Joined
Oct 4, 2013
Messages
3,434
Reaction score
3,156
Location
Jackson, MS
He has verified spark at each plug and has verified that each injector is getting 12V (ignition on) and is getting pulsed ground while cranking by jumping the individual voltage/ground circuits at the injector harness.

What I'm reading is that he also says that he gets constant ground at each injector with ignition on (not cranking). That is, he used a test light from voltage to the injector's VCM ground feed and it lit up with ignition on and flickered when cranking.

If that is what he is seeing, that doesn't seem right. To me, shouldn't there be ground supplied only when cranking?




Sent from my iPhone using Tapatalk
 

eyesi

OBS Enthusiast
Joined
Sep 21, 2017
Messages
57
Reaction score
17
Location
Moctezuma Sonora Mex
Maybe someone will know for sure, but if your VCM is providing a constant ground to each injector (instead of momentary when needed to fire) then that seems like it would be your issue.



east302, if the injectors were really grounded all time , his engine would be hydrolocked, cylinder bores full of gas,
 
Last edited:

east302

I'm Awesome
Joined
Oct 4, 2013
Messages
3,434
Reaction score
3,156
Location
Jackson, MS
That makes sense.

Maybe he can confirm that he is seeing the test light on when jumping the injector voltage/ground circuits.


Sent from my iPhone using Tapatalk
 

eyesi

OBS Enthusiast
Joined
Sep 21, 2017
Messages
57
Reaction score
17
Location
Moctezuma Sonora Mex
in my opinion, after all test and replaces you are done Nightflyer, and if you have all injectors pulsating, and all spark plugs firing, i would check power and grounds circuits at vcm, probe with another distributor cap (very known issue), before replacing vcm. Not synchronized timming you would have a p1345 dtc, or cam performance p0341 dtc, but, if vcm grounds are not ok, a lot of strange things happen, believe me, i have done lots of money fixing gm grounds
 

eyesi

OBS Enthusiast
Joined
Sep 21, 2017
Messages
57
Reaction score
17
Location
Moctezuma Sonora Mex
That makes sense.

Maybe he can confirm that he is seeing the test light on when jumping the injector voltage/ground circuits.


east302 . i dont trust in test lights for injection pulse test, i plug another well known injector outside in harness conectors, and hear them or feel them while cranking/running, if injector not pulses or continually stucks on, then i check circuits, pretty simple. Nightflyer concern is not that complicated, there is a very basic path to determine what is wrong
 
Last edited:

eyesi

OBS Enthusiast
Joined
Sep 21, 2017
Messages
57
Reaction score
17
Location
Moctezuma Sonora Mex
You must be registered for see images attach
Okay...Update:

The chevy runs....;)!!!!

The grund connections on the VCM and ignition feed are corroded. so i added some new cables like in this thread:

https://chevroletforum.com/forum/si...walkthrough-vcm-ecu-ground-wire-update-39893/

THANK YOU FOR YOUR HELP...;) ;) ;) !!!!!!
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
You must be registered for see images attach
 
Last edited:

krr711

Newbie
Joined
Oct 30, 2014
Messages
5
Reaction score
5
Hey Guys,

I'm Matthias from Bamberg, Germany. I've an 96 Tahoe (350 Vortec TBI) and a real big problem:

This is the thread from the tahoeyukonforum.com:

My car died three weeks ago while i'm driving (it was like, someone cut off the ignition) and won't start again. Nobdy in Bavaria and Germany knows why.....:(

- the battery is in a very good condition
- the car cranks very well but won't start
- the chevy has very good sparks
- the fuel pump is running and new
- fuel pressure at schrader-valve (is that the name?) is about 61psi and 63 while cranking
- changed the distributor cap, rotor, plugs and wires
- changed the ICM
- changed the CKP-sensor
- it misfires whit starting fluid (one time)
- the plugs are sometimes wet and you can (sometimes) smell gas
- the timing chain is okay (tested with turning the crankshaft and look at the distributor..the rotor moves

sometimes it seems like, that the chevy would like to start. it sounds like, that there is no pulse to the injectors.

btw: there are no codes stored in the PCM and all cables ok.


August,23:
Before this happend, the chevy runs very well...okay, sometimes rough idle (when it was very warm) and a little bit stumbling. but when i remember, the car ws often hard to start when the engine was hot....:(

I've doublechecked the spark plugs after some cranking the engine.....6 of them are dry...no fuel....:(

The fuel filter is new...changed it last month....;)

Ignition coil, cap and rotor are from delco.


August, 24:
I've spark on everthy cylinder, fuel presssure, etc..is okay.

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

It's all tested:

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

September, 11:

New injectors (mpfi) don't fix the problem....no fuel in the engine. All spark plugs are dry....:(

There are no trouble codes stored.
The ECT display the correct temperature.

September, 17:


Installed test light on each injector circuit:

Ignition on: light is lightly on
Cranking: light flickers
diconnecting VCM (red an blue): light is off

It's flickering while cranking and constantly on by ignition on.

Live data:
Now zero rpm, temperature it at 17 degrees and tps is at zero.
I've double-checked the fuel pressure...

I've tested it with another fuel pressure gauge from a friend (he has an professional one and i cant find mine)...his fuel pressure gauges reads 50psi at ignition on and engine off. While cranking it goes up to 52psi...:(

September, 20:

I've installed an other fuel pump...59psi at the schrader valve

Aaaand: no fuel at the injectors and no start..:(

The chevy wants to start with starting fluid. The first time i used too much starting fluid, so it backfires one time thru the intake..:(

September,21:

The distributor cap is from acdelco. The TPS is at 0% when closed.
I've tried it with the unpluged MAF and air temperature sensor...nothing...:(

But there is something that i've forgot: The last weeks when myy chevy works, there was something strange: when i cranked the engine, the chevy won't start. But when i stopped cranking it seems like, that the engine starts very slowly.....not all cylinders are firing. It's like one cylinder...then the other, etc. Like an old diesel..;) but when the engine works, everything is fine. good idle, etc... You know what i mean? I don't know how to explain it in english, sry...:(



east302 from the tahoeyukonforum.com helped me soo much. Thanks to him...;)!!!!!

Here is the link to the thread:
http://www.tahoeyukonforum.com/threads/96-tahoe-dies-while-driving-and-wont-start.96116/

Please: could someone help me? what can i test and look for?

Best regards from Bavaria/Germany

Matthias


p.s.: soorry fpr my bad english..;)

My 1992 Chevy had a similar event and after I checked everything it could possibly be, I replaced the pickup coil in the distributor. It fired right up. There is a resistance value that is easily found for your truck. I checked mine and it was shorting out when it got hot. Best of Luck!
 

krr711

Newbie
Joined
Oct 30, 2014
Messages
5
Reaction score
5
My 1992 Chevy had a similar event and after I checked everything it could possibly be, I replaced the pickup coil in the distributor. It fired right up. There is a resistance value that is easily found for your truck. I checked mine and it was shorting out when it got hot. Best of Luck!
 

Blackwater

Engineering Geinus
Joined
Dec 16, 2015
Messages
324
Reaction score
80
Location
Lawton, OK
Ok, In my experience I have seen a number of reasons why trucks just die and wont start. I will name the most common to the least common. Fuel: fuel pump, fuel filter, fuel regulator, injector wires pinched and grounding, bad injectors. Ignition: Timing, sparkplugs, sparkplug wires, distributer cap, coil, distributer. Others: Ignition switch, the little wire from the positive side of the battery, timing chain/gears, low or no compression, cracked block, bent piston rods, holes in pistons, rods shot out of the block or heads, valve train, crank, clogged intake, clogged exhaust.

Of each of those three categories fuel is the most common. I personally had issues with grounding of one of the injector wires which killed both injectors since they are in parallel circuit. but didn't find this out until after I changed fuel pump, fuel filter, spark plugs/ wires, distributer cap, coil, and one tow truck. I found it when I was changing plugs and wires with the breather off and after it started I left it running and placed the breather and air filter back on and it died. I started the truck without the breather and did it again. It died. I repeated the process but put my hands on the base ring and it died. I then took it off and found the ring was pinching the wire and worn away the insulation.

Another instance. I got a call from my assistant chief on my volunteer fire department stating there is a truck like yours that died and wont start again. I drove down there and sure enough the only difference was his was 4x4 and a different vin number. Even the paint was the same. I took a look at it after I used a Brush truck to hose down the truck due to him off roading. we popped the hood and I noticed the battery was not secured and bouncing around. I noticed the little wire that is normally attached to the red battery cable had been pulled out of the terminal. I told him to start it. As he went to start it I grabbed that wire and touched the pos. terminal and it started. He came back and asked what did I do and I told him watch my hand and I let go of the wire to the terminal. Truck died. I went to the tool cage and got out a connector and tools and repaired it. Afterwards, we were talking about both trucks and that's a different story.
 
Top