turboGXL

anybody ever have this condition before? I think my FCD fried my ECU but I don't know.

How do I reset my ECU? I'm experiencing NO fuel to my rear rotor. I've tried removing the FCD and resetting the codes but I'm not sure I did it right.

One last question. What component of the fuel system triggers fuel cut? I thought it was my pressure sensor but I'm not sure

thanks everyone

adamlewis

If you just want to reset it, just unplug your battery and step on the brakes for a while to drain all the power out of the system.


However, I dont know if this will fix your problem or not.

RexRyder

iTrader: (10)

ground your boost sensor to see if that will get rid of fuel cut. I know its stupid to ground any sensor, but ur **** already fucked up.

adamlewis

Or you could try that. Id try resetting the ECU first though

The Ace

If you get no fuel, then I should be looking into the fuel system, and not the ECU. Start from the injectors (primaries) and work your way back.

Fuel-cut is triggered by the boost sensor alone. If boost exceeds a pre-set limit (i.e 8,6psi for S5 TIIs), ECU cuts off fuel to the rear rotor (which of course lowers the output/rpms, which in turns leads to lower boost).

In order to reach fuel-cut, you need to reach the boost limit. If your boost sensor is fried (i.e and constantly showing 5V -> max boost all the time), then it could be this. You cannot ground your boost sensor, but you can supply 1V to its signal line to the ECU, and see if this helps....

adamlewis

I wouldnt think itd be injectors though since it just happened right after he got fuel cut.

hypntyz7

I had a car run on one rotor after a rebuild, I was pissed, thinking the engine had gonw awry...turns out is was a poor connection at the rear rotor/s primary injector,,,contact cleaner cured it, and all was good in the rotary world again...

Check the primary injectors with teh fuel system pressurized(be careful here, follow FSM guidelines) adn crank her over to check for spray on both primaries. Otherwise, it might also be a spark problem, though highly unlikely.

turboGXL

Thanks for the info/advice here everyone.
Here's what I found out.

The boost sensor tests out good at 1.89v. With the FCD installed the ECU gives a code 13 (boost sensor), w/o the fcd the ECU does not give the same code. So I believe the pressure sesnsor is fine.

I did reset the ECU and I'm still experiencing fuel cut.

I also tested the voltage coming from the ECU to the rear primary at idle, the readings indicate that the ECU was not grounding the injector. This means the ECU isn't telling the injector to open, right?

Well, I figure this means the ECU is fried. Or could I be missing something?

Thanks

The Ace

For one, the FCD is toast. Get rid of it. I think it fried the +5V ref and short-circuited to the output signal, or even worse, it short-circuited the +12V line to the signal wire In either case, you need to fix it or get a new one.

As for the injectors: yep, the ECU is actually grounding them in order to "fire" them (same thing with the fans, the fuel pump etc). You cannt have all this amperage for all accesories and mechanisms run through your ECU, so the ECU is grounding whatever it wants to operate. So, if the ECU is not grounding whatever you are checking (in this case, the injectors), then the ECU is not working properly. In order to make sure, I would check the signal AT THE ECU, and not on the injector, so that I could eliminate all intermediate wiring too...

turboGXL

The FCD is already in the trash. That's what I think caused the problem in the first place.

And the signal to the injectors WAS checked at the ECU not the injectors.

ACE: When you say the 5v ref line and 12v lines might be fried. This would cause the ECU to see NO pressure sensor signal, correct?

Do I need to be concerned with these when I install a working ECU?

Even the current ECU does not throw a code with the FCD gone now.

Thanks

The Ace

Well, actually the +5V Vref exists only as a "setup" and "reference" voltage on S4 TIIs. On my S5 TII I couldnt find a +5V wire, so I think this is the case with all S5s...

Usually what happens with the FCDs is that they short-circuit their voltage lines (+5V and +12V) to their output (signal wire going to the ECU). In case of the +5V short-circuit, you force the ECU to constantly see MAX boost (which of course means fuel-cut, which leads to engine failure VERY fast). Note that fuel-cut limit signal is around 3.7V, so you are already past the limit when the FCD is short-circuited that way.
In case the +12V is short-circuited, you not only force the ECU to "order" fuel-cut, but you are also taxing its internal fuses (I think there are internal fuses for every input line, somebody correct me if I'm wrong). Disaster is not far away.....and the ECU throws of course the "boost sensor" error....

If the ECU is not throwing an error now, this means that a) something is seriously fucked up , or b) the problem was with the FCD only, and the ECU "sees" the boost signal just fine. Check with a DMM right at the signal input on the ECU...If the ECU refuses to operate the injectors, then of course you need to do something about it, but dont count your ECU out just yet.....see if you can swap in a "good" ECU and check it (without paying for it of course). It might be something else....

turboGXL

hmm, thats food for thought. Thanks for the input everyone. I guess nothing to do but swap in a surrogate ECU for the time being.