Intermittent start problems on my’90, 740, 16v. Start problem doesn’t seem to be related to temperature (engine or outside air) or how long the car has set-it just seems like sometimes it doesn’t get starting fuel. Sometimes after setting for 2 days it starts right up & sometimes it won’t start after setting 2 minutes. Get a 2-3-2 socket 2 fault code return in test mode 1 after a no-start event. Whenever car doesn’t start it will start immediately if I spray starter fluid in the air intake and then it will run fine at idle, acceleration and cruise. I took it to a mechanic and he replaced the in-tank fuel pump. After he replaced it, the car still had intermittent start problems, he disconnected the battery to reset the computer & it worked O.K. for several weeks. Replaced the FI relay, still intermittent no start. Checked engine RPM sensor and it seems O.K.- it returns a code 3-3-1 (socket 2), and 1-4-1 (socket 6) in test mode 2.
I had a no-start and swapped the Radio noise suppression relay with the aux. fan relay & the car started right up… (yes, I read VolvoLisa's post) thought I had solved the problem, but now the car is doing the same thing again.
It seems like, after a computer reset, it would work good for quite a while, then start acting up. Now the time before it doesn’t start after a reset seems to be much shorter. Not sure where to go next. Any suggestions? I’m thinking the cold start valve or temperature sensor, but not sure I have the tools to test them or know how. I haven’t checked the pulsing of the Fuel Injectors, but I’m sure they are not pulsing or the car would start. Could this be an “air” problem? When I disconnect the AMM lead the car runs rough/won’t start, so I assume it is O.K. Not sure about the Oxygen sensor or if it would cause such symptoms. Any help or suggestions appreciated.

 

Look on the inside of the drivers side fender around the back of the headlight area.Look for a sliver block with a black module mounted to it that is the power stage.If you are in crank and no start try tapping on it and starting again.Could be the problem.The other thing would be to try to get a fuel pressure guage and install it and watch it and see if the fuel pressure drops to full Zero when the car sits.It should hold pressure while it is sitting.