Fuel injection - injectors not firing

[IronDog]

I've got a GM dual injector TBI system; has worked OK for 75K miles or so. But every now and then - when I try to start it - the injectors won't fire. No spray of gas. The fuel pump is pumping, the starter is turning, the plugs are firing. It has done it when its warm and when its cold. It did it when it was new and again this morning. Everything is working except the injectors simply aren't working. Sometimes I unplug the computer or disconnect the battery for a few minutes; I wiggle the connectors to the injectors; one time I pulled the wiring harness away from the manifold where it looked like it was trying to melt the wiring loom; once I stripped the injector wires out of the loom all the way back to the hole in the firewall where they route inside to the computer to see if there was a short. And I cuss at it. I've never found anything wrong and I've never fixed anything, but after a few minutes or even an hour or so of fiddling around with it, it fixes itself, the injectors start firing, it starts right up and runs fine! It's getting a bit inconvenient! And I'm running out of ideas except to replace the computer. Any ideas?

[rustywagoneers_com]

you may have an injector driver getting weak inside the ECM ( it is a gang of 4 transistors, one transistor running 3 transistors which operate the ground to the injector - also known as a Quad-Driver-Module )
an injector with low resistance will cause them to shut down - they sort of go into a 'protection' mode like a stereo will..
you may have a bad 12V feed up to the injectors ( inj. fuse or wiring )
you need to get a 'noid' light, which plugs in to the same connector as a TBI injector and see if it blinks the next time your truck does the no-clickee-injectors thing.. or if in fact it has given up finally..

it is also possible that the ignition module (or the wiring between it ant the ECM) is not getting the proper square wave back to the ECM, which is what the ECM uses to trigger the injectors in the first place.

best of luck, and I hope it helps at least a little

peace, Dave

[Tripwire]

Ditto what rustywagoneers_com said, you need to get ahold of an injector test lamp - they are not all that expensive. It should blink while cranking. also make sure you have 12 VDC to the injectors with the key in the on position.

Go to their web site and download the install and wiring manual - if you dont have it already

You Could have a bad pressure regulator that is stopping fuel flow - this happened to me on my 4.2

Call the companies tech support line they are very helpful. Dont get frustrated, with a minimum of test equipment you can completely test each piece of the system and find the fault

[pb]

How is the crank wire connection to the starter solenoid?