One bank no spark after engine installl

Looking at the 2.7 348 diagram (355 could be similar), the +12V supply to the middle pins of the coils has no relays or fuses; it goes from the ignition switch, goes only through the main fuse box, splices out into two wires inside the fuse box which come out at fuse box connector "F" as Yellow and Yellow/Black, Yellow (1-4) to pin 9 of inline connector 119, Yellow/Black (5-8) to pin 9 of inline connector 118. The connectors 119 and 118 are shown on the diagram to be near the ECU-s but may not be really there. After this, the Yellow and Yellow/Black both go to the inline connector No. 1 and from there to the ignition coil middle pins.

If you don't get ignition switched +12V on the middle pin of the coil for the non working bank, the main suspects are the connectors 118 (or 119) and 1.

 

If they're detecting the trigger signals from ECU pins 1 & 20 without removing the plug from the ignition power module, then indeed it could be an earthing problem (or an ECU problem).

If you can't find the specific ground for that circuit (#70046), then perhaps you can compare the resistance between pin 4 of the ignition power module and any known good ground in the engine bay, with the resisitances from the RH engine ECU plug sockets #14 and #24 to that same good ground. i.e. with the ECU and power module not plugged in. Also compare it with the O2 heater earth wire to ground. These wires are spliced together, so the resistances should be similar. If not, the splices may be faulty. If they are similar, but perhaps a little high, perhaps it is the unknown ground itself which is not secured properly.

Grounds diagram

I had a look around my car (5.2), but couldn't find a ground for my 02 sensor. Anyway, the 2.7 and 5.2 circuits are too dissimilar. When I first bought my car, I had a baffling turn indicator problem which also affected the brake and reverse lights, but only when the car was warm. I eventually found an earthing point above the LH radiator outboard support bolt. There's one on the opposite side, too.

 

I think Bob is saying that the weak signal is between the ECU and the power module (rather than to the coil pack), Miroljub.

Cheers,
Ian

 

I have not looked at the schematics and therefore have no idea how the ignition system is triggered but I'll throw this out there just in case. If the ignition is triggered by separate position sensors for each bank and if that trigger signal passes through the ECU unaltered it is possible that the air gap on the position sensor is too large. Again, probably not even a possible scenario but easy enough to check if it's remotely possible.

 

What was the reason for the rebuild? Were you having problems before this. I'm a little concerned that you didn't have a spark problem beforehand.

The mechanics said you were getting a weak ECU/power module trigger signal (and I assume it was at the right rate), but it was present. How can the air gap between sensor affect the strength of the signal from the ECU to the ignition power module? The ECU is just getting timing signals from the sensor and using them as a baseline for its output signals. It can advance/retard the timing of the spark firing to get the best engine performance. If it was a sensor gap problem, wouldn't the ECU either not get a signal and not trigger a spark or get intermittent signals and only send the occasional spark trigger? If it got any trigger signal from the sensor, the ECU would still output the same strength signal to the ignition power module (unless the ECU was faulty or there was a high resistance in the circuit (e.g. caused by a bad ground)).

Unless we're missing something here, I think your best bet would be on something being broken when the engine was removed or installed.. or someone forgot to tighten up a ground wire properly somewhere.

 

If I remember correctly this car has piggyback ecu's for fueling. They must share multiple sensors with the stock ecu's.

Have the splices been checked on everything?

 

Thats great !!!!

Yes I ground the heck out of everything

Always remember 90% of the time if a new issue arises, its something you took off..
Glad you found it

 

Oh, that says something right there.

 

It sure does!

Poor Bob had the full Gray Sharpe treatment. Glad he is getting his car exorcised

 

I wonder where that mysterious "70046" ground was. It would have been handy to know.

Anyway, good to hear it has been sorted.

 

So is Gary not so Sharpe.

What did he do!