No start: No spark, no fuel, no CEL, bad ECU?

[Berkeley91FJ80]

My 91 FJ80 is at a local mechanic and he has 'narrowed' things down to the ECU computer. How likely that he's right? Seems like something else might be signalling the ECU to disallow spark and fuel?

Background: Sometimes if the engine was hot I'd need to let it cool for 10 or 15 minutes before the truck would start. Other than that it was starting/running fine til one afternoon last week, then just nothing - she cranks but won't start. Also I had just put a bottle of 'guaranteed to pass' addititve in the fuel tank the day before. If that disloged some gunk and clogged the fuel filter, would that cause the ECU shut down the ignition?

Wondering what the most likely scenarios are before yanking the ECU.

Thanks!!

Rob

 

[SiRaDuDe]

I would serious ly read this thread, same symptoms

https://forum.ih8mud.com/80-series-tech/639406-wont-start-no-spark-after-rebuild.html


When you turn the key to the ON position does the CEL light up?

If not, unplug your AFM and try again... IF the CEL turns on with AFM unplugged, you have a faulty AFM.

If AFM is not your problem (CEL must light up on KEY ON position)... Follow these instructions for testing ignition.

 

[dakotan2]

The symptoms regarding having to let it cool are exactly the same as I had. I replaced the EFI relay and that problem went away. Sorry, no idea why you don't have any spark. Good luck!

 

[Pin_Head]

Note that the AFM does not unplug at the AFM, but fartherdown the wires. Don't touch any screws on the AFM.

 

[Kernal]

Berkeley: here's link to a 3FE diagnostics web page:

http://www.sdsysdesign.com/tlc/fsm.html

 

[CJF]

Note that the AFM does not unplug at the AFM, but fartherdown the wires. Don't touch any screws on the AFM.

Definitely don't touch any srews, but the connector *is* right at the AFM.