1988 Turbo II
FD Power FC with Banzai Racing adapter kit
720/1680 injectors

Ok so a day after my triumphant thread about getting my car running, today it didn't want to start. Yesterday (first start of a rebuilt engine) it fired right up and idled fine with no signs of any problems whatsoever.

Today though it would crank and crank and nothing would happen, not even a sputter. At first I checked to see if it was flooded but that was not the case, it's just not getting spark from the coils. I checked all the fuses with a multimeter and they were ok. The ground under the UIM is clean and I had added a ground by the ECU. A lot of this wiring had all been fine on my previous engine and had not given me any trouble. Since then I did tap into one of the four ECU ground wires (on the adapter harness) for my digital EGT gauge because I didn't want to stack another ring terminal on a bolt down there. I tapped into FD pin 4D, listed as Ground (input), but I'm not sure that's the problem since the car just ran yesterday and showed no signs of electrical problems.

After checking the fuses and checking for wet plugs, I noticed on my Power FC that I wasn't getting a tach signal. There had been some aftermarket wiring at the alternator that I then removed and that fixed the problem. So now I get a tach signal but the coils won't fire when I turn the engine over, and that's the car's current condition.

But here's the kicker: I plugged a spare CAS into the harness and spun it by hand. The coils started making spark and a tach signal showed up on my Power FC. But like I said, when I actually crank it over with the starter the coils don't fire. I checked the resistance on Ne and G terminals for both crank angle sensors (the installed one and the spare one) and they were all around 160-170 ohm, which is well within spec.

One weird thing I noticed was that my Power FC did not show any injector pulsewidth during cranking according to my logs (parameter name : Advance InjFrPr ). But I think I remember it showing pulsewidth during cranking on other cars I have logged before. TPS voltage was at maybe 1.30 volts (s4 narrow range) due to the fast idle cam and a stop screw adjustment, but adjusting the TPS voltage down didn't seem to affect anything.

Maybe I need to post this thread in the FD forum as there are a lot more Power FC users there.

 

Have someone push in the flapper on the mass airflow sensor. That was my cold start and running issues for like two years. Just a thought. Im sure it could be anything. However why not try the easy ones first right!

Also make sure that Big BAC valve hose thats under the Intake hose is hooked up..

 

Sounds like that wire that you removed was supplying 12v while cranking

Freak- he doesn't have an AFM, the PFC eliminates it

 

The wire I removed was a redundant wire from the alternator directly to the junction block I am using for my battery relocation, I guess in an effort to boost battery voltage or something. It seemed like a good idea at the time, but it must have been causing some electrical noise. I'm guessing the factory alternator wire is shielded and this wire I added was certainly not. After removing that redundant wire I even tried turning the engine over with the alternator disconnected in case it was the source of some electrical noise, but that didn't help.

I think tomorrow I am going to cut the wire that is spliced into my factory ground pin 4D.

Just to confirm, I am sure it's not a fuel pump related issue. I tried starting the car with the fuel pump diagnostic connector jumpered (fuel system pressurized) and it did not help at all.

 

This is an electrical issue. The coils & injectors need to see a constant 12V while cranking.
1. Check all your fuses.
2. Disconnect the coil connector, hook up a voltmeter and measure the voltage at the 12v wire wile having someone turn the ignition over.
3. Check to see if the commander stays lit while engaging the ignition
4. Check that you have power at the PFC , pins 1A, 1B, 1C (1C while cranking)

 

The fuses are definitely good, each fuse on the car was metered for continuity. It wouldn't hurt to double check though. I'll check for voltages on those pins when I can get somebody to help me. But there is another thing I forgot to mention:

With the key in the ON position, I measured voltage on FD pin 4E (CAS Ne signal) and FD pin 4G (CAS G signal). Both read about 5 volts. The FD FSM specifically lists that as an incorrect voltage and says it should be under 1V. Should I try swapping the crank angle sensor first? I didn't do that just because I only wanted to restab the CAS if necessary. It might be a while before I can get someone to help me test those other wires during cranking.

 

The CAS rarely go bad, but you can try swapping it.

 

I'd find out if your Main Relay is dropping out when the key is Held to Start. Maybe remove the starter trigger wire and hold the key to Start and see if you have pwr on the coils small wires or not. If you do still have pwr there, then under the same conditions, see if there is pwr at the ECU with the key HELD to start with the starter trigger wire off.

If I had power at both places as described above........then I'd see if I had REF VOLTAGE at the ECU with key held to Start. Ref voltage could also be seen/tested at the TPS or boost sensor if this PFC is similar to the stock ECU.

I also remember two other people who had similar problems with their cars. Spin spare CAS by hand....got spark. Spin CAS installed in engine.......no spark. I've no idea how they fixed their problem. Seems implausible how it could happen.

Stuff I wrote is similar to what Banzai wrote. Just added a couple of things. To confuse you and make you work harder. humor

 

I think I just figured it out a minute ago.

I left the car alone for a couple days because I just needed a break. I came back to it and was going to disconnect the starter and check for power to the coils, but nobody was around to help me. So just for the heck of it I checked voltage at the CAS pins again, and this time it was .9V (in spec).

So I said screw it and tried to start the motor. It fired right up. It ran for about 5 minutes and then died. I checked the CAS voltage and it was back at 5 volts again.

It seems to be an intermittent CAS failure, perhaps temperature related. This morning was cooler than the other day I tried to start it, and perhaps as the engine heated up some kind of electrical component lost connection inside the CAS. What an odd problem, I've never heard of that before. I'm going to swap in my spare CAS in a few minutes.