98 Tahoe with no spark
kstar24
10-13-2008, 05:08 PM
I have a 98 Tahoe 4x4, 230,000 miles 5.7 engine.
A week ago it just died going down the road. Changed the Fuel pump relay started right up.
Drove it for about 3 days, it died again. Changed the relay again, this time it didn't start. Hasn't started since.
Put a fuel pressure gage on, it was showing no pressure.
Hotwired the fuel pump relay and got 65psi on the fuel pump. But it still would not start.
The fuel gage is sitting at 3 O'clock.
Hooked up an ODBII and received com failure, missing engine controller.
I was told there is no pulse to the injectors.
Just an extra note: I did notice the last time that I started it before it died that it did hesitate to turn over, but it did. 40 miles later it just dies.
Any ideas?
thank you
A week ago it just died going down the road. Changed the Fuel pump relay started right up.
Drove it for about 3 days, it died again. Changed the relay again, this time it didn't start. Hasn't started since.
Put a fuel pressure gage on, it was showing no pressure.
Hotwired the fuel pump relay and got 65psi on the fuel pump. But it still would not start.
The fuel gage is sitting at 3 O'clock.
Hooked up an ODBII and received com failure, missing engine controller.
I was told there is no pulse to the injectors.
Just an extra note: I did notice the last time that I started it before it died that it did hesitate to turn over, but it did. 40 miles later it just dies.
Any ideas?
thank you
777stickman
10-13-2008, 07:04 PM
I have a 98 Tahoe 4x4, 230,000 miles 5.7 engine.
A week ago it just died going down the road. Changed the Fuel pump relay started right up.
Drove it for about 3 days, it died again. Changed the relay again, this time it didn't start. Hasn't started since.
Put a fuel pressure gage on, it was showing no pressure.
Hotwired the fuel pump relay and got 65psi on the fuel pump. But it still would not start.
The fuel gage is sitting at 3 O'clock.
Hooked up an ODBII and received com failure, missing engine controller.
I was told there is no pulse to the injectors.
Just an extra note: I did notice the last time that I started it before it died that it did hesitate to turn over, but it did. 40 miles later it just dies.
Any ideas?
thank you
Need to check all fuses in the under hood fuse panel especially ones labeled ECM (B, A, etc.) If you have any doubts about a fuse, replace it!
When you turn the ign sw to run do you get normal responses from the dash lites and gauges? Does the fuel pump run for 2-3 seconds? (Maybe and ign sw problem)
Were there any DTC's stored in memory? (probably can't even get there since you can't communicate with the ECM)
Next is wiring at the ECM.
Next is the ECM itself.
A week ago it just died going down the road. Changed the Fuel pump relay started right up.
Drove it for about 3 days, it died again. Changed the relay again, this time it didn't start. Hasn't started since.
Put a fuel pressure gage on, it was showing no pressure.
Hotwired the fuel pump relay and got 65psi on the fuel pump. But it still would not start.
The fuel gage is sitting at 3 O'clock.
Hooked up an ODBII and received com failure, missing engine controller.
I was told there is no pulse to the injectors.
Just an extra note: I did notice the last time that I started it before it died that it did hesitate to turn over, but it did. 40 miles later it just dies.
Any ideas?
thank you
Need to check all fuses in the under hood fuse panel especially ones labeled ECM (B, A, etc.) If you have any doubts about a fuse, replace it!
When you turn the ign sw to run do you get normal responses from the dash lites and gauges? Does the fuel pump run for 2-3 seconds? (Maybe and ign sw problem)
Were there any DTC's stored in memory? (probably can't even get there since you can't communicate with the ECM)
Next is wiring at the ECM.
Next is the ECM itself.
kstar24
10-13-2008, 07:18 PM
Thank you for the response.
All the fuses have been done, the ony way the fuel pump comes on is to hotwire the relay.
All gages and lites respond correctly except the gas gage which stays at 3 o'clock at ALL times.
Could not get to any codes.
All the fuses have been done, the ony way the fuel pump comes on is to hotwire the relay.
All gages and lites respond correctly except the gas gage which stays at 3 o'clock at ALL times.
Could not get to any codes.
777stickman
10-14-2008, 09:58 AM
In the I/P fuse block pull the "crank" fuse #8 10a.
In the underhood fuse block check these fuses for 12v power with the key in the "run" position and then in the "start" position.
1. IGN-E
2. ECM-1
3. ENG-1
If no power found, most likely ign switch.
If power is there on all 3, most likely the ECM.
In the underhood fuse block check these fuses for 12v power with the key in the "run" position and then in the "start" position.
1. IGN-E
2. ECM-1
3. ENG-1
If no power found, most likely ign switch.
If power is there on all 3, most likely the ECM.
kstar24
10-22-2008, 06:27 PM
Well we just put in a new computer, and it still will not start. Ign. switch is good. Can not hear the fuel pump engage at all. The gas gage is still sitting way past full at 3:00.
Tried to run scan and still can not get any reading. Com error.
Any other ideas?
Tried to run scan and still can not get any reading. Com error.
Any other ideas?
777stickman
10-23-2008, 10:24 AM
Bummer!!
Pull the 2 top plugs on the VCM. One is marked "white" and the other "black".
On the "white" one check for "hot batt" power (key off) on pin 21.
check for good grounds on pins 17 & 18.
On the "black" one check for power on pins 5, 13 & 18 (key in RUN).
At the DLC check pin 16 for "hot batt" power (key off).
check pin 2 for continuity between pin 11 of the "black" VCM plug.
check pins 4 & 5 for good grounds and continuity from pin 5 to pins 17 & 18 on the "white" plug.
Pull the 2 top plugs on the VCM. One is marked "white" and the other "black".
On the "white" one check for "hot batt" power (key off) on pin 21.
check for good grounds on pins 17 & 18.
On the "black" one check for power on pins 5, 13 & 18 (key in RUN).
At the DLC check pin 16 for "hot batt" power (key off).
check pin 2 for continuity between pin 11 of the "black" VCM plug.
check pins 4 & 5 for good grounds and continuity from pin 5 to pins 17 & 18 on the "white" plug.
Schrade
10-24-2008, 04:57 PM
Well we just put in a new computer, and it still will not start. Ign. switch is good. Can not hear the fuel pump engage at all. The gas gage is still sitting way past full at 3:00.
Tried to run scan and still can not get any reading. Com error.
Any other ideas?
Why did you buy a new ECM computer? You must be rich. Can I have some money?
Follow the electricity. Just like following water, except you don't get your fingers wet. If it ain't gettin' to the end of the hose, there's a hole somewhere. Work you way back to the faucet (battery).
Tried to run scan and still can not get any reading. Com error.
Any other ideas?
Why did you buy a new ECM computer? You must be rich. Can I have some money?
Follow the electricity. Just like following water, except you don't get your fingers wet. If it ain't gettin' to the end of the hose, there's a hole somewhere. Work you way back to the faucet (battery).
j cAT
10-24-2008, 07:24 PM
Well we just put in a new computer, and it still will not start. Ign. switch is good. Can not hear the fuel pump engage at all. The gas gage is still sitting way past full at 3:00.
Tried to run scan and still can not get any reading. Com error.
Any other ideas?
if the crank sensor is bad the fuel and spark will not go...must have crank position to computer to get spark.... no engine rotation the fuel pump will shut down in 2 sec...
could also be a load of other things too, what I see here though is communication error ,,,,this was a crank sensor for me...
Tried to run scan and still can not get any reading. Com error.
Any other ideas?
if the crank sensor is bad the fuel and spark will not go...must have crank position to computer to get spark.... no engine rotation the fuel pump will shut down in 2 sec...
could also be a load of other things too, what I see here though is communication error ,,,,this was a crank sensor for me...
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