S4 Turbo II no injector pulse
 

So my car has been undergoing a bit of work over the past few months. Nothing terribly major, but I've run into an issue at this point.
I have a Power FC and Banzai Racing adapter harness and when I attempt to start the engine the injectors are not pulsing despite the Power FC showing it's percieved duty cycle.

Here's what I have done so far in an attempt to correct the issue:

• Verified that the Power FC is not faulty
• Replaced the engine harness with a new OEM one
• Replaced the injectors with new DW units
• Checked the "eng inj" fuse and it's not blown
• Checked the resistors in the resistor pack and they are within spec (6.3 ohms)

I've also cleaned all of my grounds besides the starter ground. I have fuel pressure while cranking and a very strong spark from the coils. I cannot figure out whats going on, absolutely no fuel sprays from the primaries during start up. Prior to the Power FC install, I was having an issue with the engine bucking while under light load which I thought was TPS related (replaced with a new one now).
Never had any issues starting and idling though, just random lean spots while going over bumps and turning. Also if I had the car idling to operating temp, I would open the door and sit down and it would die as if the engine was out of fuel and then start right back up no problem (I figured this was related with the issue of going lean over bumpy roads, hence the reason I replaced the old broken harness thinking there was a short).

Any ideas? I'm stumped.

Thanks,
Steven

Have you verified 12V at the injectors with the key on IGN?

No I have not. Will I have to remove the upper intake manifold to verify at the connectors or should I probe wires elsewhere? Which pins are proper to check at the ecu? I don't have my manual handy (at work).

Probe at the respective ECU pins. 3C, 3F, 3E and 3H.

I will do this after work and post the results.

Thank you

Check voltage at the injector connectors. The PFC only supplies ground to open the injectors.

Also since you have a PFC the injector wire are 4W, 4X, 4Y, 4Z, but again that is not for checking voltage.

Pull the UIM, use a spare injector connector on the injectors and supply 12V & ground , listen for a click on each and check for spray on the secondaries.

Fuel pump should prime as soon as you turn the key to the on position, it should not just have fuel pressure while cranking. Double check your connection to the COR.

I will try this method when it cools down a bit outside. As far as the fuel pump is concerned, it primes when the key is switched on and then runs as it should during cranking.

Thanks

Still no luck. I checked each injector for a click and there's no issue with them. Is there anything in the harness that would cause my above mentioned symptoms (original post prior to pfc install) and then in turn prevent the ground pulse from making the injectors open after the pfc install? The car ran prior to this, just had an odd grounding issue or maybe a short somewhere.

Are you focusing on the primary injectors as the secondaries don't work unless under load and above 3800 rpm.

Do you have spark while cranking?

Happen to have a spare crank angle sensor? Plug it in, spin it and see if you hear the injectors work.

I do have spark while cranking also I have a spare cas on another engine actually. I'll do this now.

I spun the cas and I could here the injectors working (clicks and mainly hissing sounds from each as I spun it). I installed that cas and tried the same method with the original one, same results. I then tried to crank the car with my extra one, no start.

Are you certain that you are getting fuel?

Sounds like you are losing voltage to the ECU or the injectors while cranking. Power to the injectors comes from the main relay.

If the main relay was bad, the fuel pump wouldn't prime with key on correct? Could a CPU cold solder issue cause these symptoms? The warning light clock worked when it wanted to and my horn function was intermittent as well.

Thank you

Edit: the clock's issue is in the warning light panel itself, but the horn's intermittent issue could be related to the odd loss of power going over bumps in the road if the CPU points need to be re-soldered correct?

CPU doesn't play a role. And in a stock situation w/the key to on the Engine fuse powers the Circuit Opening Relay which powers the pump.

Ah, thank you for the insight. As far as your previous post, I am certain I am getting fuel. I tested this by removing the feed line and having the car turn over. As far as the main relay is concerned, I will purchase another now then and see what happens when it arrives.

Thanks

In my past comment I meant to say "w/the car running and the key to on." But if you want to bypass the Main Relay all you would need to do is remove the four wire plug to the relay, which has two plugs in all, and jumper the B/G to B/Y and B/W to W/L. You can then see if the relay was faulty and thus the cause of your problem although don't leave the jumpers in place as this could eventually drain the battery.

Fuel pump will prime since you are getting power to the ECU and COR with the key in the on position, ths issue appears to be when you turn the key to start. This is when it is critical that the power to the ECU does not get interupted. Power is supplied by the main relay to pin 1C.

A quick test is to push start the car. If it starts and runs then you have narrowed down your search. Keep in mind that all the fuel injector testing has dumped a lot of fuel into your engine.

I attempted to push start the car a couple of times with no luck starting it. I also replaced the main relay anyway just in case. Is there anything else that would interfere with power getting to the ECU during start up? Thank you and Satch both for your help so far.

Have you checked the voltage at pin 1C (for your aftermarket Power FC) w/key to start? The voltage should be 12 volts w/key to on but upon startup the voltage would drop as voltage is supplied to the starter. Voltage would normally drop down to around 9 volts or so. If it is too low then it might not be enough to power the PFC thus causing your problem.

It drops to about 10.5 V while the car is attempting to start according to the Power FC.

The voltage should be more than adequate.

Have your primary injectors ever worked properly after the installation of the PFC?

No they have not. Since installing it, the car will not start. I thought it was the fault of the Power FC originally so I had it tested in a FD locally and the car started up no problem. I followed the instructions very closely and verified that my wiring was correct after recieving the adapter harness.

The FD car you tested it in I would assume had a PFC to begin with and you just switched yours for the existing one?

Correct. Rotorsports transferred its map to my power fc and started the car.

Are you certain you have don't have the primary injector wiring wired to the secondary wiring and vis versa? A simple continuity test would validate that this aspect of the wiring is correct or not.

I will check again. Im not sure how this mistake couldve been made being that prior to installing the adapter harness and PFC the car ran. I'll go check the wiring from the factory harness through the adapter to the power fc.

Let's go all the way back to basics:

Did you modify the trailiing coil? Did you verify that both trailing coils are firing correctly?

What is the boost reading o the commander with the ignition on?

The trailing coils should be fine. I trust your work. I will verify trailing spark just in case of course, I did verify leading spark though. I'll check the boost reading in the afternoon while I take a look at the wiring as stated earlier (it started raining).

Ok so we did the trailing coil for you.

I am starting to think that there is no problem with the injectors getting power. The fact that you hear the injectors with the spare CAS, yet the car does not start while push starting is pointing back to the original questions being asked. Check your fuel pressure. When you were installing the new engine harness did you disconnect the fuel lines? Have you verified that you do not have the supply and return mixed up.

The PFC is supplying the ground to the injectors, if they were not getting power while cranking, there would be no injector duty reading.

have u tried removing the power fc and trying to start it?

I verified fuel pressure before, and I am sure the lines are installed properly. Feed from fuel filter into primary rail, primary rail to secondary rail, and secondary rail to return. I will check fuel pressure again tonight just in case though. It can't hurt since I'm going to remove the upper manifold anyway while I'm rechecking the grounds. Is there anything in the charging harness that would impede power reaching the injectors properly during start up other than the main relay? Also I was under the impression that the duty cycle reading on the commander was just a calculation according to target spray volume and injector size.

Thanks for your help. Hopefully I can get the car started soon.

Removing the Power FC would require me to remove the adapter harness and I'd have to buy another factory trailing coil. So no I have not.

bump

Can't help you if you do not answer the questions being asked.

Sorry, I've been preparing for a trip and checking the boost reading with the key on slipped my mind. I did however check the fuel lines and pressure, everything is okay there. I will check the boost reading tomorrow morning and post before I head out of town.

Thank you

If you checked your fuel pressure, what is it?

Pull your plugs are they wet or dry?

I'm back from my vacation now. I ended up not having time to post this before my (very) early flight to Seattle. Here's the information that you needed from me:

Boost Reading - 40/42 mmHg before cranking and while cranking it reads 58/60 mmHg

Fuel Pressure - 45 psi when priming and 42.5 psi while cranking

Plugs - Dry

Also, I'm not sure whether or not this would help but my injector duty cycle reads 10/11% under initial cranking and as the engine turns for a while it goes down to 2/2.4%

My cranking speed is 238 rpm.

-Thanks

You do know that your primary rail is the short one right? Not trying to be smart, this a common mistake on this forum.

Pull the hose off the primary rail (short) and prime the car into a gas container, verify flow.

It really sounds like you have your feed and supply mixed up. Does the diaphragm on the primary rail have vacuum nipple? There are j-spec rails with reverse flow.

I know that my primary rail is the one closest to the engine. No offense taken, I appreciate being thorough. I'm 99% positive that the feed and return lines are properly installed but since I'm not looking at it right now I will not claim 100% correct installation. I did prime the feed line into a small container intitially before connecting my fuel pressure tester (just to make sure before wasting time). The rails are usdm flowing from right to left on the primary and left to right on the secondary (looking from the driver side). Also I'm not positive on the presence of a vacuum nipple, the only feature that stood out to me was the banjo bolt mod done during the rebuild (I guess).

-Thank you

I shouldn't be my injectors, the engine wouldn't start with the factory injectors and I replaced them with new aftermarket ones just to make sure. I've also checked them by rotating the CAS at this point and they all make noise. The factory ones click when 12v and ground is applied to the as well.

-Thanks

I am out of ideas without seeing the car. Everything reading from the commander is fine. The PFC is grounding the injectors to open them.

I guess you could try installing jumpers in the connector to the resistor pack to bypass it temporarily and see if the issue is there, but the fact that the spare CAS is firing them, means the resistor pack should not be the issue and the PFC is getting the signal. The only thing I can possibly think of is fuel routing.

I am sure it is something simple, but again not being able to see the car makes it more of a guessing game.

Edit: switch the fuel line just for kicks to rule that out. It can't hurt anything.

I most likely is something very simple, but what is beyond me at this point. I wish I were closer to your shop. I really appreciate your help. I'll switch the fuel lines tomorrow afternoon. If I cannot get the car to start by this weekend then I will arrange it to be transported to you for this issue and a few maintenance things. What's your turn around time looking like normally? Message me please.

-Thank you

I am sure it is something that could be sorted out in a few hours. We always have 8-10 cars in the shop for rebuilds, but things like this I just fix and then go back to the larger projects. In other words we would be able turn it around quickly.

Alright sounds good, I'll give Elaine a call and setup a plan and transport next week If I don't get it started. Thanks again.