ECM Issues - No Start

[XfireZ51]

Originally Posted by Macroblock

Awesome!

Verifying that the injectors are working is actually straightforward. Remove the Yellow or Gray 22-way Connector to the ECM. Turn the key to ON. One at a time, jump a wire from the (-) Battery Post to positions 1, 2, 3, 7, 8 12, 13 and 18 on the Connector. An injector that makes an audible click, is likely OK.

The injectors used in the early years of the ZR1 are susceptible to damage from ethanol in the fuel (not normally found in premium blends). The injectors develop shorts within their respective solenoid windings. Bad injectors will not produce a healthy click (a totally failed injector will not click). A current measurement can be used to verify the health status of an injector but the simple 'click' test provides discernible results.

Verifying the ECM is sending a (-) signal to each injector, without pulling the plenum, involves opening the ECM and ---CAREFULLY---checking each DRAIN PIN on the 8 Power MOSFETS. Use a 12 volt test light connected to (+) post of the battery. Have a friend turn the engine over (not literally). The test light should blink for each transistor. The ECM PC Board is marked "D" to guide you.

It is also possible to skin some of the jackets on the wires that feed the injectors and utilize a 12v test light, but by doing this you damage the wiring. To repair, coat the bare copper with heated solder and while still hot apply vinyl electrical tape.

In the case at hand, the ECM is unfortunately at fault. It looks like I.C. Component number U13 has failed (Sequential Injection Controller). As a result, only Injector 6 gets a (-) signal from the ECM.

Used this procedure today to check injector pulsing. Worked well. It may have helped w a knock issue I have been pursuing for some time, but not sure if this was what solved it for me or not.

[Macroblock]

Verifying that the primary injectors are working is actually straightforward:

Remove the Yellow or Gray 22-way Connector to the ECM. Turn the key to ON. One at a time, jump a wire from the (-) Battery Post to positions 1, 2, 3, 7, 8, 12, 13 and 18 on the Connector. An injector that makes an audible click, is likely OK.

To check the primary and secondary injectors together, remove the Brown 22-way Connector to the ECM. Jump positions 16, 17, 21 and 22 from the connector to GND.

Then remove the Yellow or Gray 22-way Connector to the ECM. Turn the key to ON. One at a time, jump a wire from the (-) Battery Post to positions 1, 2, 3, 7, 8, 12, 13 and 18 on the Connector. Both the primary and secondary injectors that make an audible click together, are likely OK.

To check only the secondaries remove Injector 1 Fuse while doing the above tests.

See page 6E3-A-5 of Factory Service Manual.

[Macroblock]

The ECM is out of the way of most of the engine heat so, the Arduino should be ok, sandwiched between the ECM's 2 PC boards.

I've used Arduinos on hundreds of devices, many in harsh environments, so I am confident it will be fine.

As I test a few hundred iterations of the code I wrote, I will monitor the Arduino for signs of heat distress.

[Macroblock]

I do have great photos, but I wasn't able to upload them to this thread unfortunately. I suspect, I'll have to post them elsewhere and link them.

[-=Jeff=-]

Originally Posted by Macroblock

The ECM is out of the way of most of the engine heat so, the Arduino should be ok, sandwiched between the ECM's 2 PC boards.

I've used Arduinos on hundreds of devices, many in harsh environments, so I am confident it will be fine.

As I test a few hundred iterations of the code I wrote, I will monitor the Arduino for signs of heat distress.

Great to hear. I have an Arduino Due in the dash with a 5? LCD to replace the DIC lights

[Macroblock]

Originally Posted by XfireZ51

Used this procedure today to check injector pulsing. Worked well. It may have helped w a knock issue I have been pursuing for some time, but not sure if this was what solved it for me or not.

I have found that if the LT5 has a dirty, clogged or malfunctioning injector, this manual 'force' activation technique can sometimes help.

[Macroblock]

Just discovered a serious error in the 1990 "RED" Edition of the Factory Service Manual that relates to the Camshaft Sensor.

Code 31 on page 6E3-A-50 describes the sensor as having a 0-5 volt output.
This is incorrect. It is Ignition Voltage which is usually 11-14 volts.

The correct voltage "(about 12 volts)" is referred to on page 6E3-C1-3.

This matters if you're reworking the ECM like I am at the moment!

[dredgeguy]

Macroblock, have been watching this thread with fascination, no clue about the technical side of this but impressed that you certainly understand and have fixed the one component that is rare, expensive and could shut us down if it goes south. Well done and thank you for posting!! I think this would make for a great article with photos for the Heart of the Beast and as Ccmano (Hans) suggested, a great side business if you have the time and enjoy what you do.

[XfireZ51]

Originally Posted by Macroblock

Verifying that the primary injectors are working is actually straightforward:

Remove the Yellow or Gray 22-way Connector to the ECM. Turn the key to ON. One at a time, jump a wire from the (-) Battery Post to positions 1, 2, 3, 7, 8, 12, 13 and 18 on the Connector. An injector that makes an audible click, is likely OK.

To check the primary and secondary injectors together, remove the Brown 22-way Connector to the ECM. Jump positions 16, 17, 21 and 22 from the connector to GND.

Then remove the Yellow or Gray 22-way Connector to the ECM. Turn the key to ON. One at a time, jump a wire from the (-) Battery Post to positions 1, 2, 3, 7, 8, 12, 13 and 18 on the Connector. Both the primary and secondary injectors that make an audible click together, are likely OK.

To check only the secondaries remove Injector 1 Fuse while doing the above tests.

See page 6E3-A-5 of Factory Service Manual.

What year FSM are u using? My 91 FSM doesn't have proc at that page.
So to clarify, are Brown pins 16,17,21,22 all grounded simultaneously before moving onto Yellow/Gray connector? Or are they done individually w corresponding pins on Yellow/Gray?

[-=Jeff=-]

I think he is using a 1990 FSM