No spark 5.7L

[skylark]

Are your plugs so fouled out that they won't fire?

 

[Lloyd Delmont]

New plugs

 

[Schurkey]

1988 K2500 5.7l. Is not firing.New coil,new distributer,new plug wires.

the truck just quit while driving like i turned the switch

I also checked the ignition switch. The rotor button is turning while trying to start.

New plugs

Do you have power at the coil and ignition module when the key is turned to "Run"? If the wire harness is in good condition, power from the coil also powers the module. But wires can break, insulation gets damaged leading to wire corrosion, etc. For that matter, you could have popped a fuse protecting the ignition system.

If you still have fuel spray but no spark, the ECM is getting an RPM signal from the module.

It is a bypass ignition.

Huh? WHAT is a "bypass ignition"?

 

[evilunclegrimace]

Do you have power at the coil and ignition module when the key is turned to "Run"? If the wire harness is in good condition, power from the coil also powers the module. But wires can break, insulation gets damaged leading to wire corrosion, etc. For that matter, you could have popped a fuse protecting the ignition system.

If you still have fuel spray but no spark, the ECM is getting an RPM signal from the module.


Huh? WHAT is a "bypass ignition"?

It is what GM called the ignition system on the TBI trucks. If you look at schematic you will see that the terminals on the ICM are labeled. Term A is Reference Low. B on the ICM is connected to D5 on the ECM. That is what is labeled Bypass. Term C is Reference and Term D is EST.

 

[Matt Conner]

I had a similar problem and ended up replacing the ECM after doing literally everything I could think of, no issues since

 

[Lloyd Delmont]

Yes ,i do have spray, and power going to coil at run postion and at start postion. Let me mention this I have been trying to help my friend over the phone. I starting to lose confidence i what he is telling. I am going sunday to put my own eyes on it. We will see where thats goes.

 

[PlayingWithTBI]

Good idea, it's hard to diagnose stuff long distance, take a scanner with you.