Esc And Knock Sensor Diagnostics

[arizhnt]

1990 GMC 5.7L TBI

 

I have fought this problem for the last 2 months. The first instance was in a parking lot-no start. As a test for fuel/electrical system diag I shot starting fluid doewn the tbi-started and ran. No problems for approx 2 weeks then-no start. It will start occasionally with starting fluid but no all the time. Then it started to die at stop lights-intermittant. Sometimes would restart with starting fluid-sometimes not. Checked and found code 34, tested the MAP sensor and got a range of readings, replaced MAP sensor-still no start, checked and found corrosion in the cap-alternating cylinders, cleaned and engine started. Repeated 2 more times, replaced the plugs. Inside of the distributor was rusty so I replaced the distributor and coil. Started right up bu could not see the timing mark clearly. Shut down the engine and cleaned the mark-has not started since. I have 12v at the injectors, fuel to the TBI ( I also replaced the fuel pump earlier), no fault codes, no spark. I tested the knock sensor on the engine-64K ohms (sensor terminal to the engine block I removed the sensor and bench tested:33K to 35K ohms, Retested this a.m. 100K ohms ( on the bench ), the wire to the sensor was replaced-it is wired directly from the sensor to the ESC, 2 ohms resistance from terminal to terminal. I cannot find any diagnostics for the ESC unit, (in fact Haynes does not show it in the wiring diagragm). I am at a loss as to the cause of failure on this truck.

 

Where do I go from here?

[Draenor]

Have you check for slack in the timing chain?

 

Pulled the tan(?) wire from the Distributor at the firewall when setting the timing?

[Draenor]

Quantum post......

 

 

 

 

 

 

 

 

 

 

Deja Vu....

[arizhnt]

Have you check for slack in the timing chain?

 

Pulled the tan(?) wire from the Distributor at the firewall when setting the timing?

 

 

The timing chain is tight.

 

There is no tan wire comming off of the distributor.

[bill190]

Well I would be off to the GM dealer to order a set of factory service manuals (4 books for set). Then use these to get that distributor adjusted as it should be.

 

Then you will find all the additional troubleshooting and diagnostic information you could ever hope for. And all for your specific vehicle.

 

As to spraying starter fluid and it starting, this says to me you should check the fuel system. Use the factory service manuals for this.

[bill190]

Here are the various things to check in the fuel system. The factory manuals will give you specific testing instructions for your specific vehicle, but this is a general overview...

 

http://www.asashop.org/autoinc/june98/techtotech.htm