Another FA24 Challenging Issue

RESOLVED:

Three issues in total. 1st one made the other two hard to find and the 3rd one was causing the issue refereneced in this post

1) Poor crimp in AC1 engine connector on Bank 1 inlet cam signal. Random fall out of signal.

2) Missing injector o-ring on port injector to intake manifold (minor issue)

3) As a final follow up to this post. I went back and did the ignition test and YES the direct injectors fired! Wiggling the main engine connector would allow me to change this effect, so that really helped me narrow down the issue. I found two loose grounds under the intake manifold. My assumption is that the ground for the DI box to trigger was floating, and with the coils firing (and drawing current) that would come up enough to trigger the DI box when the ground wasn't making good contact.

Seems to be solved.

Yes I have two of these things with M150's incase you have seen my other posts.

Back story:

Stock engine, endurance car

This car was purchased with an M150 already running it. Car ran well but lost a motor due to oil starvation. We had a local shop swap motors because I was focused on the primary (other) car. Car started and loaded fine with the new (used) engine. But when we got on track it started to miss at high RPM. closed loop was full negative, and was still too rich. Found out the car was originally tuned with FA20 injectors. Ok, no big deal. New plugs, back to FA20 injectors. Now car doesn't run at all. I find a broken wire to the Bank 1 inlet cam position, resolved that. Car now runs but SUPER rich, even through lambda doesnt show it. As if one cylinder is running rich and another lean (etc). Lots of smoke with no coolant/oil smell.

Next I flip to 100% secondary injection, still doesn't run. So I disconnect the DI box and the car fires right up and runs fine. So on port injection, with the M150 set to 100% port it ran seemingly ok. As soon as a plug the DI box in, the car dies... even though I have 0 direct injection commanded!

Next I replace the DI box, DI pump and DI injectors. Same thing. Car will run, but super rich (despite lambda saying otherwise) and will die idling. Unplug DI box, move to 100% secondary.. car runs fine.

Of course I am tempted to replace the secondary injectors with aftermarket/higher flow rate and just run the car on port. But this really has me baffled. I would prefer the fuel efficiency advantages of the DI as well.

I did have another person (MoTeC dealer) look at the logs remotely and he didnt catch anything.

What happens if you use the output test function for each of the primary and secondary fuel injectors?

Same thing with Fuel Test and Ignition Test, you can use this to cut fuel or ignition to individual cylinders to isolate faults like this.

a DAQ data export from Tune 1.5 would be a lot more helpful to diagnose something like this.

One possibility worth a mention that I have seen multiple times now - the ecu usually gets the blame of course...

The GT86 driver boxes ground through their case/mounting bracket, and there are now many clueless companies out there promoting aftermarket "lightweight brackets" made from anodized aluminium or powder coated steel which if you're unlucky, nicely isolates the driver from ground.

So if it has an aftermarket bracket I would look at that closely, you wouldnt be the first to be caught by one of them.

I am definitely not blaming the ECU. It actually likely something else.

@Adam I will double check that. Its a stock bracket, but that doesn't mean its grounded properly.

@OMS I went through that and everything seemed as normal EXCEPT when i ran the ignition test ALL of the direct injectors and spill valve solenoid were firing (!!!). I sent this information to MoTeC but so far with out any real response. Its been weeks.

The engine harness seems to have been designed such that you can't plug the wrong connector into the wrong injector by controling length, but last night I was poking around and MAYBE you could stretch bank 1 and swap them. So I am going to run the output test on those two injectors and more time to make sure they are right.

How would the IGNITION test cause the INJECTORS to fire -- you must have a serious wiring issue.

I went back and double checked a few things. Let's forget about the ignition trigger injectors thing, I definitely can not get it to repeat that.

But when I ran an output test everything operated as it should. Except the primary fuel. None of the injectors fired. Then randomly I could get one to fire for 5-10 cycles the it would stop. Ingnitoin and secondary operated as designed.

Reminder I am using an M150 with the factory DI box. Also this car ran for about a season.

Clearly there is a primary fuel issue, but I am not sure how to sort that other than to replace the DI box which I did. I tried a noid light on the output of the M150 to the DI box, but none of the outputs seem to have a duty cycle.. they are either on or off. I assume this is correct and is managed differently because of the DI box.

I am wondering if the DI box won't fire the injectors until it seems fuel pressure etc.

The M150 uses ignition resources to drive the EDU box and they are high active.

So if there's a path to ground the injector is off, when there's no path to ground the current source 'requests' the EDU to switch the injector.

It sounds like you have a wiring issue. These cars are pretty notorious for wiring issues in the engine harness due to age.

Do you have access to a picoscope?

Direct fuel pressure is measured by the ECU not the EDU box.

Another thing to check - ECU Pin B5 (may be labelled something like 35-5 in Motec docs) controls the EDU relay, this needs to be low for the pump and DI injectors to work.

I left out the car is rewired and has a pdm. I did check for +12 at the two pins (b2+ and b+) on the DI unit. Pdm shows enabled for that output.