1975 2.0 FI stock motor...

#1...disconnect the FI connector at the injector and the RPM does not change...Disconnect the injectors one at a time and 2,3,4 all make a big difference in RPM...

To help in trouble shooting, what is the voltage to the connector ??? Can I measure it or is it too small i.e. milivoltage...

By looking at the Haynes wiring diagram, the signal comes direct from the ECU...Therefore if I have no signal or weak signal at the injector, what are my options...

This injector is brand new from recent engine rebuild...But could be bad, will check operation...

Any thoughts...Need opinions...

2-OH!

Maybe test each injector differently. Pull one out at a time, put the injector into a glass jar and check it's spray pattern. If one is different than the others, swap it to see if it's injector related or connection related. The FI trigger points work in pairs. A problem there would likely effect 2 injectors at a time.

The easiest thing to do from this point since you have locked down the problem child, is to swap it out. i.e. Take and swap #1 and #2 injectors around. Start the engine and pull the #1 lead. If the idle still doesn't drop, then you most likely have a broken wire to the injector, bad terminal or something. If the idle drops when you pull #1 after the swap, bad injector. Pull #2 to test that theory. If idle doesn't drop, you just moved problem child from spot 1 to spot 2, replace injector. It is a lamemans test, but works.

You could use a noid lite too but Dan quickie method is the easiest.

I also like to take out the injectors and testing the spray pattern to verify how they are working. Use a glass jar and killer the power to the dizzy so there is no sparks if you do this. Look for a nice fan spray of fuel when you turn over the motor.

Geoff

There are at least three possible points of failure here if your #1 cyl seems dead:

1. ECU
2. Wiring Harness/Plug
3. Injector

Note that I'm assuming you have normal compression on this cylinder and also that you have spark. If you cannot isolate the problem to the FI system, recheck the compression and spark.

The ECU is unlikely to be the cause of the problem. D-Jet uses grouped injection, where the 1&3 and 2&4 injectors are fired from the same circuits in the ECU. If #3 is working, it's very unlikely that #1 (at the ECU plug) isn't getting a signal.

Wiring harnesses on these cars are getting into really bad shape as time passes. The easiest way to check if there's a harness and/or ECU problem is to buy a "Noid" light at your local FLAPS (about $7). Make sure you get the "Bosch" light. Disconnect the injector and plug in the Noid light while the car is running. Is it flashing? Yes? Then the ECU and the wiring harness are good. No? Pull the wiring harness plug at the ECU and use a DMM to check the continuity of the connection between the ECU plug and the injector plug. You also need to check the ground connection at the injector plug (the ground cluster is at the back of the engine). Both good? Then your ECU has a problem. Either bad? Your wiring harness has a fault. Check at both plugs, and also at the ground cluster. All of the pin-outs are on my web page.

If your Noid light is flashing and the cylinder is still dead, check the injector for spray. Pull it and stick it in a jar and re-start the motor. You're working with raw gas here so take all needed fire precautions. No spray? You have a dead injector. Spray? Well, then it isn't the FI system that's causing the dead cylinder. Check compression and spark.

BTW, I agree with the other postings that pulling the injector FIRST and looking at the spray pattern is the fastest way to determine if the FI system is at fault, if you're still fishing for the cause. I keep a Noid light in my glove compartment, along with a cheap $10 DMM for those mysterious roadside diagnostic sessions.