zenbeast

Injectors not getting voltage pluse from ECU. I have a new ECU that came out of a running car.
1. I have checked the grounds.
2. I have checked the injectors.
3. I have checked the Fuel Pump and the flow all the way to the far end of the rails. the far side of the regulator.
4. I have spark.

To sum it up i just need gas pulses so my injectors will feed the ports.

Maybe my air flow meter.. ?

What would keep the ECU from sending pulses.

Any help would be great..
So who can get this car running..

zenbeast

I was looking at the Wire diagram and noticed that the Main Relay supplies the neg side of the injectors. I think that was one of the grounds i checked. lol..

I will test this out tomorrow.

elmayimbe4eva27

iTrader: (2)

Based on your profile it says you have an S5 RX7. The injectors are supplied 12v from the MAIN RELAY via a B/Y wire. Check your EGI INJ and COMP fuses. Make sure the B/Y wire at the MAIN RELAY has 12v w/ key on.

zenbeast

I just updated my info.
86 S4 NA .. not S5..

Your post sounds just like what i was thinking. I will have to look up what the comp fuse does. ..

satch

iTrader: (1)

The injectors get voltage from the B/Y wire supplied by the Main Relay w/key to on and they also get voltage from the Green wires from the ECU w/key to on and when the ECU injector driver needs to turn on the injectors the ECU sends a brief ground signal to the injector to complete the circuit. If the ECU is not sending the ground signal then it could be a function of the CAS. Also, only the primaries will get the ground signal unless the engine is above 3800 rpm and under load and then the secondaries also receive a ground signal so they can fire.

The B/Y wire from the relay is powered by the EGI INJ fuse but this supplies constant voltage to the injector w/key to on and is not the wire that supplies the ground signal.

zenbeast

Ok i just took the main relay out and it works. I get continuity when powered and none when no power.. So i will check to see if the plugs are getting the power to pass after fight night..

And if they have power then what... check from thew relay to the ecu?

I thinking...

satch

iTrader: (1)

Pin 3E at the ECU (smallest plug has 8 wires in all) is the wire that sends the ground to the front primary injector and is colored Light Green. Pin 3C which is Light Green/Black is the ground signal for the rear primary injector. W/key to on both of these wires will have battery voltage at their respective pins and w/key to start the voltage would drop to about 8 volts or so in a normal situation. Check these two wires under both situations explained above.

elmayimbe4eva27

iTrader: (2)

There's also one other fuse to check; 15A Engine. Its located inside the car, under the drivers foot.

Correct me if i'm wrong here Satch but, early S4 models came with low-impedance injectors and late S4 and all S5 models came with high-impedance injectors, right? If i'm correct then to the OP, you have low-impedance injectors and you're using a resistor pack for your injectors, which should be located on the passenger side somewhere around and in-between the shock tower and MAF. The connector on the resistor pack can also be used to check that you are getting 12v w/ key on up to that point.

I had a similar issue as yours, my problem was i didn't have a resistor pack installed when i did my swap
Thanks to Satch, he helped me the whole way through that mess. So i thank him and recommend listening to him as well

zenbeast

My solenoid resistor pack is testing out fine.
Main relay is getting 12v to pass fine..
I am going to go out and test the resistor pack for voltage on the plug right now.. It will probably be fine

So whats next?

zenbeast

I have checked the voltage all the way to the to the .. well secondary injectors..
Main relay-->resistor pack-->secondary injectors..

So i am back on the other side..
NOTE: i have changed the ECU out.. and I am getting coil spark , so my CAS seems to be doing its job.
The CAS puts the timming in to the ECU and it provides the other side of the injectors...

What am i missing..
Who wants to meet up and plug in my ECU to see if their car starts on it...lol

I am not sure what else there is...

satch

iTrader: (1)

Did you check the ECU as suggested in post #7 or not?

zenbeast

I have checked the ECU at pin 3c and 3e.. They are getting the volts.
But it think i may know the issue..
I do not have a fuel pump test gage.. So when i tested i just did a visual check on the fuel was moving.

But i found a gage and made a test meter.. I tested this out using water pressure from the house first..
It seems the after hooking this up and testing the fuel pump pressure.. I do not have pressure..

So fuel moves but i dont think its at the 28 psi.. i think was the minimum...

So i need a fuel pump...

myfc3s

iTrader: (2)

Back track a little, does your car idle or does it even turn on? have you checked to see if your spark plugs are wet after cranking it a few times, have you checked to see if your fuel pump filter is not clogged better yet a new fuel filter?

zenbeast

I am guessing the fuel filter is under the car? Or is there an access panel.. Like the pump?

blmcquig

iTrader: (15)

fuel filter on an FC is by the clutch slave cylinder. its kinda a pain to change (until you get an FD, then you will remember how easy the FC fuel filter was to get to)
open the hood, stand on the drivers side, and look towards the trans bell housing. the filter is on the chassis next to it.

zenbeast

Ok i checked the fuel filter... its fine... In fact i could blow through it.. i know yumm..
So i researched my testing of the pressure.. I was testing the wrong line... I was testing the return line..
So i found a good pic here and tested the left line.. and im getting 39lbs of pressure of of the line..

So I guess im back to the Why am i not getting the fuel through the primary injectors... All i can think of is the ECU..
Since i have tested all the way to the ecu.. pin 3C and what 3E... Maybe the CAS... But i doubt it.. since i have spark.. Honest...

I am stumped ..

satch

iTrader: (1)

Pin 3C and 3E should drop to 8 volts or so with the engine running or attempting to start the car. Do yours? I believe you stated they have battery voltage w/key to on but they also need to behave as mentioned above.

zenbeast

Ok so the "Plug side" is 12volts neg.. since they come from the injectors and drop off at 3C and 3E pins..

and the Pins coming out of the ECU at 3C and 3E are about 8 volts pos..
When i am cranking.. Right.

satch

iTrader: (1)

The two pins would be 12 volts w/key to on and about 8 volts while cranking.

zenbeast

I have test 3C and 3E they start out at 12 and when cranking they go to 8 volts.

So what is next.. What would tell the ecu not to send volts to the injectors..

satch

iTrader: (1)

Pin 3C and 3E "are the ECU" so the ECU is not the problem then (breathe sigh of relief). I'm not sure why you believe the primary injectors are not pulsing when you try to start the car but if they are not then the plug that attaches to the injectors are either loose, cracked or perhaps the injectors are stuck in a single position such as either open or closed. The wires that run to the injector might also be damaged as well.

zenbeast

I took the injectors out and made test/cleaning bench device. Just to make sure that they are clean and work.

So the plug wires 3E n 3C are from the injectors.
NOTE: injectors are just coils/solenoids . So the volts from there shows that the plugs and wires are good. i get the 12 v and 8 v ...

The ECU sends the other voltage.. Probably by grounding out. Right..

zenbeast

zenbeast

I think i will pull off the intake and d a primary injector test.. I think it said to wire the injectors tight and put a towel under them and crank.. to check for gas flow.

Any thing else i should need to know?

satch

iTrader: (1)

The 8 volts is the ground signal and because it occurs so fast your multimeter cannot possibly see it so it shows somewhere inbetween 12 volts and 0 volts.