marlaman

Hey it's been a while since i've been active on here since attending school and working takes up most of my normal playtime, anywhoo~~

My car is only currently firing the primary fuel injector for the front rotor, the injectors are all good as i did have them cleaned and tested by Rich at Cruzin a while back. So i assume somwhere in the wiring harness there is a break in the wire.

So my question is this, Could i just rewire both the primary fuel injectors from the ECU(By running fresh wires from the ECU to the FI's, BUT there is only 1 wire per injector on the S5n/a ECU--so would i just ground the other wire to the chassis--because in the FSM it says the sending signal to the injectors IS ~~12V's) or do the leads from the ECU go into some type of sending unit? I can't find a damn thing in my FSM or Haynes manual about it so any help would be greatly appriciated, I am very sick of running on 1 rotor and wondering how much of a toll it will take on the engine.

Anyway that's for you help i appriciate it.
Matt

Oh by the way, anybody have any tricks to remove the sway bar end links? those are stuck on like Stink on Sh*t and i don't have access to a lift or jack.

WAYNE88N/A

First the easy part- I just used a rotary grinder with a dremel bit to remove my old bar link bushings. That's if you're talking about the bushings, lol....If the weight of the car is still on the sway bar, I wouldn't recommend trying to bang the bolts out. Some **** could start flying...

Now to the hard part- How do you know that only the front injector is firing? Have you read the injectors electrically from the ECU and found a dead circuit there? Cleaning the injectors does NOT extend the useful lives of these things- they do go bad. If she's bad (injector coil blown), you'll see it at the ECU- the voltage will not be present at the pin on that particular injector circuit. If the coil's good, but the ECU circuit is bad (not "dropping" the ground), you'll see a steady 12v (or about 14v with engine running) that doesn't fall as the engine is revved...

ilike2eatricers

Take a look at my thread. I had one of my primary injectors fail on me and went through alot of BS for a simple solution.

https://www.rx7club.com/showthread.p...njector+driver

RotaryResurrection and Wayne88N/A helped me solved the problem. They are gurus that helped me understand fully how the injector circuits work.!

patman

iTrader: (3)

injectors all have 1 positive wire from ecu and the other side goes to ground which is a ring terminal mounted on top of the rear rotorhousing. the positive wire goes from ecu to injector resistor pack to injectors.

pat

RotaryEvolution

iTrader: (30)

i would test the + wire to see if it does actually have good continuity and to be sure it is not grounding out on the block or chassis and test the ground circuit, if both are ok then see if you can find a good injector to test with.

patman

iTrader: (3)

my bet is with the grounds...they go bad all the time

RotaryEvolution

iTrader: (30)

but only affecting one circuit sounds a little odd.

RETed

For a bunch of guys who have no problem figuring out freshmen college calculus, you are all wrong about the fuel injectors.
Stock ECU spits out a pull-to-ground signal, while the other side of the fuel injector is +12VDC.


-Ted

patman

iTrader: (3)

i didnt say i didnt have a problem figuring it out.... calculus sucks.

are you sure about that? I thought the ground terminal that bolted onto the rotorhousings was the injector grounds?

either way, he still has to test the wiring.

my bad, guess i dont know everyting after all. lol.

HAILERS

You need to go to the ECU with a digital meter. Pull the plug off and take a look at 3W, 3X, 3Y, and 3Z. With the key to ON.

You should see battery voltage at each one. 3Y is the REAR PRIMARY, the one you indicate is not working *somehow*. If there is battery voltage there, then most likely the wiring is good at ahd through the fuel injector.

Like the man said, it's the ECU and its fuel injector drivers that pulse a ground to the fuel injector circuit. Maybe you have a bad ECU, Maybe not. Maybe a bad fuel injector. Swap the rear primary with a secondary injector.

Or like Wayne suggested, connect the ECU plug up and backprobe the 3Y with the meter. Start the engine and rev the engine. The voltage should drop at 3Y if and when you rev the engine. Compare the voltage drop to the good injector. IF it does not drop........probably a bad ECU driver.

About the ring terminal that is the grounds for the ECU that is on top of the engines rear rotor housing.........it's the ground for the guts of the ECU , but since the engine starts and runs, it must be a good ground.

You NEED to rid yourself of ANY idea of grounding one of the wires of the fuel injectors to the chassis. Your gonna whack something big time before the fuses blow.

marlaman

Thanks for the info All, I know for a fack because of backprobing--and also the fact that every once in a while the injector does fire--so i'm leading at the theroy of a ground for the primary rear injector being good but having a bad ground or voltage wire---one or either of them could be broken, i know my ecu is fine, i have done the tests.--aside from the one wher ei rev it up, that's a good idea--thanks!

Hailers, Thanks for the advice, i allready have tried 6 different injectors on every one of the clips and all my injectors are good.

So knowing that somewhere in the wiring harness the wires could be broken for the injector, what should i do to fix this annoyance?

Thanks,
Matt

WAYNE88N/A

Figure out which two pins on the small plug at the ECU are the grounds (sorry, don't have the schismos with me now), run a TEMPORARY wire of at least 14 gauge from each pin (just push it in the back like you would a meter probe, make sure it's fairly tight) and screw/bolt it to a ground near the ECU using ring terminals, if you wish...

Start the car again, see if anything changes. If it does, you probably have a bad/dirty/loose/corroded ground out there on that rear rotor housing. Clean/repair as necessary...