The idle shutdown mechanism depends on how the ECM is set up... there are many ways this can be done. Running it at high idle might or might not override the idle shutdown, dependent on how the parameters are set. If you have ambient air temperature override, you can tape a hand warmer to the temperature sensor.
If you mean the fuel pump relay, it is in the front row on the relay rack, to the extreme left (drivers side in US models.) It is a big white relay. You may download a diagram of Volvo 740 relays from the Internet. I always keep a set of spare relays with me because of failure issues due to overheating.
My 2007 Volvo uses .5-.6 gph at idle (600 rpm), if I set it for a hi idle (900 rpm) it uses 1-1.1 gph.
Idle is set by the computer.
how do I set the timing on a BMW 740
Idle is automatically set by the computer with the use of an idle motor.
The idle speed is set at the factory and is NOT adjustable.
To set the idle, adjust the carburetor.
The idle is computer controlled
You have two fuel pumps and filters on this car. One set is in the gas tank that can be reached by way of the trunk . There's a plate that can be removed to give you access to change them out. It's a little tricky, but not to bad to change them out. The other set is under the car approximately under the drivers seat. These look like two canisters are very easy to change out,
The timing can be adjusted by loosing the 2 bolts that hold the distributor on any pre-1989 740s. Be sure your timing belt is installed properly too. Another note here, the harmonic balancer on the 4 cyl Volvo has a rubber mounting between the inner part that attaches to the crankshaft and the outer part that the drive belts go around. They are known to slip. If your timing is way off, put a small white paint mark on the crank pulley and rev the engine a few times while watching it with a timing light. If it is changing positions a lot then you are going to have to replace the balancer before it comes completely apart. you cannot set the timing in a 740. if it doesn't run, it's not right. No one said it did not run. Timing belts can be off as many as three teeth and still run. Over 35 years in the Volvo business myself. Do note the question was about a 1990 Model that is a crankshaft position sensor fired car. The timing is not adjustable on a 1989 or later as the above answer states, PRE-1989
The timing chain is slowly set as the mechanic tightens the thread.