Volvo 1995 2.9 liter. Had to replace the timing belt and valves after tensioner failure. Followed the timing alignment procedures. Starts and runs smoothly through the rpm range. After engine warms up, cranks but will not start. Maybe not related but wiring to the temperature sensor associated with the dymanic camshaft timing adjustor was broken then spliced back together.
Any ideas on where to begin the diagnosis? What kinds of computer controlled adjustments can be expected after warm up? "Vacuum advance" etc.

 

This sounds like an electrical issue. Since you have a splice there, I would re-do this splice. Do not solder in wires that can get very hot or that vibrate. A butt (mechanical) connection/crimping is the recommended method.

Have you pulled any codes yet?

 

Thanks Henry. I agree with the electrical issue. We did pull the codes and they were temperature sensor signal missing and lean operation. I am not sure if we created the signal missing issue when checking the butt junction. I need to clear the codes and repeat the opeational tests. Do you have any idea what a lack of temperature signal would do to the engine control? Stop fuel injection? Shift the timing etc. I have not found any logic diagrams explaining how the temperature signal is used in the control of the engine.

 

Which Engine Control system do you have? My '98 has Motronic 4.4.

Is you fan behaving erratically? You can test the ECT (Engine Coolant Temperature) Sensor, by measuring its resistance at certain points. You can download the procedure from k-jet.org

Usually, missing signal, or wrong signal (too hot, too cold) from ECT Sensor causes many issues.

ECU uses different strategies for cold or hot conditions. Wrong ECT signal affects fuel injector pulse width, advance / retard (hot/cold) timing, EVAP, EGR, Idle speed, Transmission. etc. If ECU establishes an "open-loop" it will ignore O2 Sensor signal and dump too much fuel, which may cause a no-start.

 

The temp sensor controls injector duration. It could be a connector problem, I would clean and tighten the connector first.

Now, a total lack of feed from the sensor, the computer will measure the time the engine is running and use predetermined temp/time points for an estimated engine temp, this is for the first 10-15 minutes. There can be a problem with this on subsequent hot starts, the computer is assuming the engine is cold when it actually is not.

A sensor that is working but not feeding the correct data, well, can affect fuel consumption and eventually the catalytic convertor, whether lean or rich.

Volvo does have a scan tool that could read live data, including the engine coolant temp., something very nice to have I guess but only a dealership could afford.

DanR '94 964 356,000 miles (122,000 on the new engine)