nolimit

Ok people need a little advice. 3.0 complete rebuild and have fuel issues. The fuel pump is operating I have checked fuel at cold start injector and to the fuel rails but will not start. the injectors were serviced by witchunter so everything I know to check I have checked. You can pour a little fuel into the throttle body and she fires right up and runs until thats gone. Any ideas.

Dan.3

possibly a loose ground somewhere. If you have gone over you ground connections yet, I would start with that.

nolimit

Thanks. I'm not sure were all the grounds should be. This truck was in pieces when I got it but should be able to locate on wiring diagram.

sb5walker

If you have fuel pressure, but no fuel in the cylinders, the injectors aren't firing. Have you checked for power at the injectors when the ignition is on? If no power, trace wire back to IG2 terminal of ignition switch.

The ecu fires the injectors by grounding them, so if the injectors have power, check for the grounding pulses while someone is cranking the motor. Try a test light between the two injector leads or a continuity tester (or ohmmeter) between the not-hot injector lead and a good ground, but the pulses are very brief, something on the order of 30 milliseconds, so your instrument will have to be fast-responding to catch it. (There is only a not-hot injector lead if all the injectors are disconnected. Because they are wired in parallel, if you just disconnect one injector, power from IG2 will go through the connected injector, to the terminal on the ecu, and back up the wire to the disconnected injector, making both leads hot.)

If you're not sure, the troubleshooting section of the fsm has an alternative method of troubleshooting the injector circuit of the 3VZE on page IG2-194:
http://personal.utulsa.edu/~nathan-b...86troubles.pdf

That technique doesn't check for grounding pulses but verifies that voltage from the injectors does make it all the way to terminals #10 and #20 at the ecu when ignition is on. If those terminals are hot, but the injectors are not firing, then you can be fairly sure the ecu is not grounding them.

A way to check whether the injectors are firing is to place the metal rod of a mechanics stethoscope against the side of the injector while someone is cranking the motor - the clicks will be loud and clear if it's firing.

Here's what normally should happen: The distributor generates crankshaft position (NE) and camshaft position (G1 & G2) signals, which are sent to the corresponding terminals on the ecu (grounded by G-). Based on those, the ecu turns around and sends an ignition pulse to the igniter on IGT. The igniter, if it is working right, sends a pulse back to the ecu on IGF - that's a check to make sure ignition is firing. The ecu, receiving the IGF pulse, pulses ground on #10 and #20 to fire the injectors.

A problem with any of those components or the connections between them, or any key system grounds, will result in no injector grounding pulses.

First, check the connections at the distributor and igniter. Sometimes a pin gets pushed back in a connector and doesn't make contact, so check for that. Be sure to verify that the igniter ground is good.

Here's a wiring diagram for the ignition circuit:
http://personal.utulsa.edu/~nathan-b.../9systemci.pdf

If you haven't found the problem, you'll need to check all the signal rotor clearances and signal coil resistances in the distributor and check the igniter. Here's a good post with a method for doing that:
https://www.yotatech.com/forums/f2/n...89-95-a-10543/

But - those are specs for the 92-95 distributor, so see this post for the earlier distributor specs:
https://www.yotatech.com/forums/f116.../#post51126569

And also see the fsm instructions for checking signal rotor gap and coil resistance, but keep in mind the different specs in the above post.
http://personal.utulsa.edu/~nathan-b...12onvehicl.pdf

See also page EG2–195 of the EFI troubleshooting section of the fsm:
http://personal.utulsa.edu/~nathan-b...86troubles.pdf

Igniters can be killed by hooking battery or jumper cable up backwards, and they can be killed by low resistance on the coil, so may as well check both coil circuits while you have the ohmmeter in the neighborhood.

If you STILL haven't found the trouble, check that all the wires involved have continuity, and check all ecu grounds, especially E1, E01 & E02, and if necessary check all of the grounds, engine and chassis.

nolimit

Thanks for that info. I'll be back at it tommorow. Will post what I find.