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Trying to diagnose the no start condition in my J10. Getting a code 34, fuel is spraying but not firing. Any ideas?
I bought a new ignition module and spark tester and will be checking those later. I am thinking that I have a no spark condition but as I understand the tbi the ecm needs to see a spark to fire the injectors.
82 J10
77 J10 Golden Eagle 401
88 GW
You know it's bad when your car is on the EPA's 10 most wanted list!
The TBI ECM needs to see the distributor signal. It doesn't necessarily need to see the spark. If the injectors are firing, the signal is getting from the distributor to the ECM. So you know the distributor is working, as is the ECM.
So if you have the computer controlling a GM HEI module, it could be between the computer and the module, the module is bad, or there's a problem between the module and the coil. If you're running a normal Motorcraft ignition system, either the signal isn't getting from the distributor to the ignition module, the ignition module is bad, or there's a problem getting from the module to the coil.
The cheapest thing to start with is checking all of the wires to make sure everything is connected the way it's supposed to be. If you have a spare ignition module, swapping it in will tell you if the one that's installed is bad.
There are two sets of two wires going between the distributor and the ECU (usually bundled together). One carries the trigger signal from the distributor to the computer. The other set carries the coil trigger signal (once the computer determined delay has been added) from the ECU back to the module in the distributor. Check those second two wires end to end for continuity.
Check the module in the distributor. It's possible that it has gone bad and won't trigger the coil. A replacement ignition module isn't terribly expensive and is useful in a box of spare parts you keep in the truck.
Check the wires that go from the 7 pin module to the coil to ensure they're connected and working properly.
If all else fails, it's possible that the computer has a bad connection or is otherwise broken in some way. If you have a spare computer, give it a whirl.
I'd be surprised if the problem was anywhere but one of those places.