Are the fuel injectors powered by the ecu or by a external power source?

[nismo13s]

I think i may have found my crank no start problem. I had a tech from my shop come over and we found that the injector had power going to them when the ignition was on, then we unpluged the ecu and 1 of the wires had no power. the second wire still had power ???. so we turn the ignition off and remove the key. and we still had power to the second wire ???. now what i need to find out is...

What powers the fuel injectors? the ecu or a external power source?

Does the ecu ground the injectors to fire the injector?

If the fuel injector power souce is EXTERNAL does it have a fuse or what?

This has to be may problem because the injectors have to get grounded somewhere.so can someone please help me. I have a drift day on sunday and probably wont make but i need to try or else im out $100.00. ohhh and the other thing is that there is a possibllity that i fried my ecu. so if someone has a ecu let me know how much and i might have to buy it.Thanks

Modified by nismo13s at 8:21 PM 5/4/2006
Modified by nismo13s at 11:28 AM 5/23/2006

[Bluefire]

Ecu does not power the directly injectors. But the ecu switches a relay that powers the injectors. Actually I don't even know what motor your talking about but, thats how the SII RB25 is

-BLuefire

[Joe]

basically yes

series 1 is powered by a switched source (use something from the fuse box). series 2 is al self contained (you dont have to do anything)

[Sil240]

I have the same prob, i have voltage going to my injectors all the time,The ecu is supposed to ground out one side of the injector to fireI still cant get my car to start because of this same probIf you have any solution please please let me [email protected]

[nismo13s]

basically yes

series 1 is powered by a switched source (use something from the fuse box). series 2 is al self contained (you dont have to do anything)

My motor is a 94 rb20det, i dont know what series it is. does the rb20 and rb25 use basically the same style of electrical for the injectors.

can you be more detail on where i can find these power sources. do you have any wire color and position in car?

[Darius]

I don't know about the RB20, but the Series 1 RB25 has a plug with 7 wires that connects the injector wiring harness to the ecu harness. The 7th wire (gray) is for 12VDC "ON" power to the injectors. I temporarily have my wire hooked directly to the battery, but I just started it up so that's not the best. I would find a wire near the fuse box that has "ON" power and run that injector power wire to it.

If the RB20 only has a 6 wire plug like the Series 2 RB25, then the injectors are powered thru the ecu. IF you are not getting power to any injectors and the key is "ON", check your relays and if those are good, and continuity to the injector harness is good, then it might be an ecu issue. If it is an ecu problem, that's a good excuse to get a power fc.

Someone with an RB20 will be better able to help you out if my comments don't apply.

[Wulfgang]

The injectors on the RB20 have all their high sides going to the battery through a fuse. Or at least that's how they should be. Depending on who did your wiring, you may have something different.

The low side is just like all other cars... it goes to the ECU. The ECU has internal switches (transistors) that ground the low sides to drive the injectors.

If you were to unplug your ECU and measure the voltage at both sides of each injector, you would see 12 V everywhere. Also, when the ECU is plugged in but the ignition is off, you should see 12 V everywhere. This is just because no current is flowing and so there is therefore no voltage drop across the injector.

The only easy way to test the ECU is to turn the CAS by hand (engine not turning, but ignition on) and listen for the injectors clicking. The more sophistocated way would be to check the waveform at the injector low side with an o-scope.

[Wulfgang]

In case that wasn't clear, I am just trying to say that even tho the ECU does ground the injectors to fire them, it is virtually impossible to "check" the ECU function with just a multimeter because the ECU never holds the ground statically. Spinning the CAS is the only option unless you have an o-scope.

[tuppidsay]

You could just go to Harbor Freight and pick up a set of noid lights for $10. U just plug the light into the injector harness connector and try to start the motor. If it blinks your computer is properly grounding the circuit and firing the injector. Just better than messing with the cas in my opinion.

[nismo13s]

ok, well like i posted earlier i have power to both sides of my injectors. i put a noid light on it and the it doesnt light up. i pulled the cas and turned it by hand and it did not up, but i did hear the injectors clicking. can anyone lead me in the right direction. i have not one clue what to do.

[Wulfgang]

I think you're on the wrong page... you might try looking elsewhere before trying to force an injector problem.

For example, does your fuel pump work? Do you have spark?

[nismo13s]

ok, so i have checked everything, and the car still wont start. i have check my electrical, fuel, everything. this is what i have so far.1 i have spark, pull coil packs and check for spark2 i have fuel pressure and all injectors are firing. plugs get soaked.3 I have checked base timing and the timing is dead on.4 all grounds and all vac lines are connected.5 self test on ecu got 55 all good.

so now i have no clue where to go from here. has anyone had or has heard of any symptoms like these. any help is appreciated. thanks for looking

[Darius]

Check to make sure everything is in order with your IGN and ECCU relays. I had the same issues with everything else working and it turned out my ECU was not automatically grounding itself. I jumpered a wire from the orange wire on the eccu relay to ground and it fired right up. For the time being I will be using the jumper wire until I can afford/justify a PFC.

[nismo13s]

Thanks, I will give that a shot. If it doesnt work then i am back to square 1. I will post up later.

[nismo13s]

ok, well i jumped the orange wire at my eccs relay to ground and nothing happened, it still cranked and cranked and crank...before i jumped the wires the ecu light was on and it went off when cranking now the light on the ecu does not turn on when i put the key in the "on" position, when i crank the light will flash quick and then go off . I am now back at square one. I am not sure but i think my ecu is fried I mean I have spark, i have fuel, i have air, fuel lines are good. so what else could it be. again any help is appreciated. I have been on this for a month now and i really want to drive my car again. so if anyone has ANY ANNNNY ideas please let me know. Thanks.
Modified by nismo13s at 11:30 AM 5/23/2006

[Sil240]

It may not be that your ECU is fried, Because I have the same exact problem and I have 2 ecu's from totatly diff places.I highly doubt that both of them are friedMy car still is not running.Have NO clue why not