I have a Non Turbo S4, I was wondering if anybody has tested the resistance of the fuel injector wiring harnesses. What I did is measured the injector harness from the ECU plug to the injector plug. The positive leads measured .006 ohms the negative leads on the other hand measured 0.504 ohms across all 4 grounds. Has anybody else have similar experience? In my mind the resistance in the negative side means poor ground. Can someone confirm the resistance values of the negative lead on the fuel-injector plug.

 

.5 ohms is not very much at all. As for the .006 most good leads have more resistance than that. I have a decent Fluke and i think just my leads touching is .1. If you look through most flow charts they normally ask for values under 5 ohms.

 

You confuse me witht the way your checked things. The wire(s) from the ECU to the fuel injector plugs ARE the grounds for the injectors.

The OTHER wire on the injectors is the POWER wire for the injectors.

So if you ohm'd out the wire from the injector(s) plug(s) to the ECU small plug and got say .4 ohms or near that, that is just fine. I'm talking ohming it out from one end of each wire to the other end of said wire.

I don't know if your car is a early version with the solenoid resistor package in the power side of the injector wiring or not so I'm not real sure what you did there.

Negative wire colors would be........light green........light green/red........light green/black .......and light green/white.

On the cars without the solenoid resistor package ........all the injector power wires are the same.........black/yellow.

The color of the power side of the injector wires for cars with the solenoid resistor package .................well I'll post a jpg later showing those wire colors.

 

I think the power wires are technically supposed to be black/white (according to the diagrams) but after all this time they have turned to yellow.

 

If the car is a ealy one then the circuit looks like this jpg below. The power wires for the injectors are what you see there. Brown/yellow, brown/red, brown/white and plain old brown.

Each resistor in the resistor package is 6ohms. The solenoid resistor package looks like the one in the second jpg. Not my car just a jpg stolen off this site.

Third jpg is another of the early wiring. Somewhat better than the first jpg.

 

The reason I was testing the wire resistance from the ECU Plug to the fuel injector plug is because I was replacing the fuel injector connectors and used crimp connections to wire in the new fuel injector pigtails. According to peoples opinions they tell me that every-time you introduce a crimp connector it is like introducing a small resistor inside the circuit.

My car does not have fuel injector resistor box.

I understand now that the operation of the fuel injectors is ground triggered.

 

Next time maybe check the resistance prior to putting new connectors/pigtails on? I wouldn't expect much of any added resistance if crimped right. I mean if I ohm'd out from one end of the wire to the other I'd expect no more than ????? say 0.4 ohms.

 

The resistance from one end of the wire to the other, i'm referring to the 4 injector wires from ECU side leading to the injectors (green wires), measured 0.006 ohms when tested. The other wire in the injector plug "ground" measured 0.510 ohms when touching the engine block.

 

The ground wire you mention is the POWER wire to make the injectors work. It's color would be black with a yellow stripe.

That wire is also connected to the lead and trail coil assy along with going to a condenser near those assy and also is connected to the Main Relay but if the key is OFF then it's not really going to anything inside the main relay. It goes to all four of the fuel injectors. All the black/yellow are spliced together.

So if you disconnected all four injector plug............unplugged both coil assy along with the condenser........and the key is off.........I'd expect an open circuit if you ohmd one black/yellow injector wire to ground. Like no ohms at all.

For the black yellow wire on each injector connector just put the key to ON and see if there is batt voltage on each of the black/yellow. Done. No more action needed. IF those wire were shorted to gnd the EGI fuse would blow each time the key was put to ON.

 

The .550 ohms your reading is coming from either the coil assys and or the condenser. Not worth looking to see which. Just check for power on that wire.

 

Sorry to revive such an old thread, but while reading and then checking my car i found some info that people who have low impedance injectors and looking to run high impedance injectors might find useful.

I bought the car 2.5 years ago with 153,000 miles on it and i've always wondered what the hell the green plug connector is... The previous owner had replaced the secondary injectors with ones from a company called "oside tiger" but hadn't replaced the primaries. A few months into ownership and my car began flooding being hard to start after being turned off (going to the store or whatever).... i later replaced the primaries myself with the injectors he included that he hadnt installed, I guess the low impedance injectors were affected by the lack of resistor box to the point they were flooding the car... It seems like this company oside tiger provided a connector to plug into the spot the resistor pack plugged into. I cannot say for sure but it seems like all the connector does is connect all the wires together... I cant see a fuse or anything. So apparently i've been running high-impedance injectors for 25,000 miles with no issues, and the work-around to allowing them to run on a low impedance Rx7 is to just connect all the resistor box wires together?

Included a picture of my ECU for reference as some seem to be concerned that this may burn out the ecu, i believe its been replaced but i dont know if its a pre or post 87-1/2 ecu.