Help needed! Serious problems with Thema S3 V6 (or maybe not?!)

[Tore]

Have some serious problems with my S3 Thema V6. This is what happened...
Started the car as normal, after 10 sec. it stopped! Never happened before. Tryed to start but it was only running on starter motor. The car is in daily use.

Started checking the timing, ignition, and fuelpressure. Everything was ok!
Since I have spare engine I tryed changing one part at the time. Every el.part is changed (yes! even fuses, cpu, relays etc) and it still doesn't start.

Next thing I tested was flushing fuel from both injectorrails (disconnect the pressure regulator) into a big reservoir. THEN the engine starts and idle at ca. 2000 rpm but running ok. If I speed up, the engine dies! as it should do because the missing fuelpressure.

Aha... I think...this is just some water somewhere in the fuelsystem.... So I connect everything back and try starting the engine. Guess what...It does NOT start! The sparkpluggs is soaked in fuel.
And I can do this test on and on... same thing happends...engine starts

All help/hints is good news!

Looking forward hearing from you out there
Best regards
Tore

[pol]

Tore,

Just a few things to check i can think of:

*Did you change the injectors? maybe the injector leaks fuel into the cylinder if the fuel pressure is high .
Then there is to much fuel, the sparkplug gets wet and cannot fire no more.
*Are all the injectors connected as should be? If you connect a LED on top of the injector wires, you can see if they receive an electric pulse from the ECU (this is a little trick i used once) or use an oscilloscope.
*Use the right spark plugs,clean and new, i don't know on a V6 but it is very critical on my Turbo16V.
*is the air intake of the fuel tank OK? underpressure in the tank can be the cause of not enough fuel, especially when you rev up. (however i doubt this one because you wrote the sparkplugs are soaked.)
*mass air flow meter OK? air intake OK?

Good luck,

Pol

[Tore]

Hi,

Thank you for mail.
I have changed all the electrical parts one by one.
When measuring the the fuel pressure I read 3,0 Bar. This is correct according to manual, when engine is running. If I speed up, the pressure increase about 0,5 Bar. This is to inject a little more fuel. this is also correct.

Anybody who has any kind of troubleshooting list or link at internet? Can I measure something somewhere at the cpu?
Have also measured wires from sensors to cpu

I have no more ideas!

Tore

[alan]

when i had a similar problem on another car (not thema much older) it was the ecu that had failed and was pumping in too much fuel by leaving some injectors open all the time

[Tore]

But why is the engine running with the fuel lines disconnected in front of the pressure regulator?

[Leo]

Hello Tore,
The most common problem with Thema fuel injection is that the wiring to the water temperature sensor (blue top) break. Can you check with a multimeter to see if there is a "resistance" in the cable? The symptom is that the mixture is too rich - sounds like your symptom. The engine will usually start though and the problem shows up when the engine has warmed up and the mixture should be weakened.

Good luck, Leo

[Tore]

Thanks Leo,
I have checked the sensor with a multimeter. It's ok. Have also replaced the sensor with a resistor similar to 0°C and 80°C. Nothing change.

Different parameters are controlling the opening time of the injector. Anybody who knows which? Looks like the time must be too long. Since the fuelpressure is 3.0 Bar, I think it must be the pulsewidth......

Any Alfa 164 people out there with this kind of problens?

Problems moving the car since it's automatic.

Regards Tore

[Leo]

Hello Tore,
I just remembered that when we replaced the engine in a freind's Thema Turbo we put the temperature sensor connector onto the idle stabiliser valve and vice-versa. The mixture was too rich for the engine to start. So that suggests that a short in the cable to the temperature sensor could cause the symptom, but if you have checked the cable then that seems unlikely.
Is the ECU a Bosch Motronic system? If the air-mass sensor is the "hot-wire" type perhaps that has failed, I have not worked on such a device and do not have any resistance values for it.

Leo

[Paddy]

Hello Tore,
Had a similar problem on a 16v Turbo and finally traced it to the mass airflow unit which was flooding the engine. Had to replace it - unfortunately expensive.
Paddy

[FJB]

The sensors - and their wirings!!
When the water temp. sensor on my new Thema S3 2.0 i.e. was down, the engine would neither run properly nor efficiently.
And it could not find its correct idle.
When fallen down from the warming-up-1300-idle to 800, it always nearly died when I pushed the accelerator.
I changed the sensor by taking the one out of my '92-S2 2.0 i.e., and everything was OK.
FJB.