Tbi swap build thread

[brontotx]

Originally Posted by rfmaster

Turn ignition key into RUN position (do not crank). With a DVM measure voltage (with respect to engine ground) on both injector terminals - you should have voltage (11.5 to about 12Vdc) on both sides of the connector. Repeat for for both connectors.

When you pour a bit of gas into TB do you get engine firing up???

//RF

Sorry, RF, but I respectfully disagree. Again, I'm no expert (I'm worse - I'm an engineer), but my understanding is that one side of each injector always has the 12V+ and the ground is switched/pulsed to the other terminal/side of the connectors by the ECM. Thus, testing for voltage across both injector connector terminals as you suggested will not show 12V (I just checked my truck and confirmed the lack of 12V across the injector connector terminals when in RUN).

With the key in RUN position, you should be able to measure 12V from the red wire on one connector (or the white wire on the other connector) to an engine or chassis ground, but not to the other connector terminal.

In regard to pouring gas into the TB, he said it would start in post #186.

cjracing: The relationship between the ignition module in the dizzy and the injectors is that the module tells the ECM that the engine is spinning (and at what RPM). The ECM needs to check that the engine is spinning because it is a potentially very dangerous situation if the ECM allows the injectors to fire (i.e.,release fuel into the TB) when the key is in the RUN or START positions and the engine isn't spinning. Since FB72 said his engine would start when he poured gas into the TB, the ignition module is working fine and it is my belief that his problem is (1) an ECM problem, (2) an open in the wiring between the ECM and the injector connector, or (3) a stuck/defective injector.

Since the injectors are basically solenoids, I reiterate my earlier suggestion to apply a ground to the non-12V+ terminal of the connector to see if the injector will fire. With a confirmed 12V+ on one injector terminal and a ground to the engine or chassis on the other, the solenoid/injector should click and allow fuel to flow. If fuel doesn't flow, either (1) the injector is stuck or defective or (2) there is no fuel pressure in the injector pod. If fuel does flow, then the problem is upstream of the injector connector in the ECM or wiring. While I've never tried this test, I don't see why it wouldn't work, nor do I think it risks harming anything.

That is my $0.02 and please understand that I am not trying to offend anyone or debate their advice - I'm simply trying to help.

Mark