i posted here abuut my nonrunning 740 about a month ago. it turned out it had poor compression becuase of a blown headgasket and warped head. i had the head straightened, decked and it got a valve job. the piston rings were all replaced and the motor rebuilt with all new gaskets. now the starter cranks in the on position and the car still doesnt fire. the timing is set. the wire to the oil pressure sender is missing and the same with the coolant temp sensor in the block...will this keep it from starting?

 

Can't say. Go to www.stepbystepvolvo.com and download free guide to 740 no-starts and see if that will help.

 

Agreed. Since your car had a multiple amount of failures, the problem could be anything at this point. Based on what you've described, your car has had failures in different regions of the engine (head gasket, oil sensor, wiring, coolant temp sensor...). If this is true, it is very likely that other systems in your car have failed as well (ignition system, fuses, fuel pump, etc).

 

In this kind of situation, it's very difficult to make a diagnosis. There have been so many things done, and the people who did them along the way have to have done them well enough... The good thing is that it's cranking over.
But, to the point of your question: The Oil Pressure sender will not effect the starting, but the Cooland Temp. Sensor in the block WILL. There are actually three such sensors, two for the FI/computer, and one for the gauge. The guage is not important for starting, the other two are. They are located under the second and third intake manifold bellows and are difficult to get to with the manifold in place. But they have to be functioning to signal the computer.

 

Is it even possible to get to the aft temp sensor on aB21E with the manifold in place? Seeing it is hard enough, getting a socket on it was nearly impossible I tried for 30 minutes and gave up, mainly because I felt I could never get the new one in without cross threading it. .