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Ultimate TPI install - injectors not getting signal

Just finished installing the ultimate TPI Fitech setup on my 1990 TPI Corvette. (38351 kit which uses factory injectors, so not throttle body)

On intitial start I'm getting no injector pulse. Have a test light and nothing - the injector connector does have 12V on orange and 3.5V on black which looks to be correct.

Fault codes coming up for all injectors as shown

Any ideas please?

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I did notice that the ignition fuse feeds nothing and doesnt even have an output cable or connector, but the ignition feed does go directly to the relay which then feeds the other circuits. Not sure if it is meant to feed anything as maybe usedon another kit

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What is the voltage reading on the handheld while cranking?  When voltage drops much below 11 during cranking, the injectors will likely not fire.  Also check your key wire connection.  If it is loosing power during cranking, the unit is shutting off.


Thanks Austin

I have direct fed the fuse box with 12V feed and fully charged battery and still nothing

Well, I decide to start disconnecting circuits to eliminate potential isses. Unplug the electric fans, no change, unplug the transmission plug (Not VSS) and the car starts!


It was getting spark, but no injector pulse, but now the injector pulse is there and it runs. I plug the transmission lead back in and it still starts - really don't know whats going on

700r4 lockup harness?

Btw, the only voltage that is a concern is the battery line on handheld dashboard.  If it falls below 10.5 to 11v during crank, the injectors can't open.

Correct, the 700R4 lockup harness. But thinking about it a bit more, because there is a lot of slack in the wiring loom in places  (because its a generic wiring loom) I had folded back and cable tied a number of the harneses together to make the loom look tidy. I cut away the cable ties to unplug the transmission connectors, so do wonder if the wiring loom where cable tied together had a signal being cancelled out by voltage or signal on another loom or something similar?