I am growing attached to my wife's 87 740/t
I'm not sure if it is fear or pity.
I am not nor will i ever be a great mechanic, but the previous owners of this car were just cruel in their neglect.
She was just refusing to idle, and would stall every time you turned your head.
Making a looong story shorter, I replaced the IAC, the hoses coming to and from. Cleaned and re-gasketed the Throttle body, set the TPS to specs, and it was better but not good enough.
So i took a breath and wrenched myself into the timing cover bottom cover looked like a pit bull had used it for a chew toy, the Harmonic balancer was spun, the bottom timing belt sprocket's nub was broken off, and all of the front engine seals had RTV sealant on them to stop the oil leaks.
So i ordered parts let's call it $235 and we're not done.
The timing belt wanted to walk off the cam sprocket turns out i had a square belt in a round sprocket, and the intermediate shaft sprocket, had a weird ridge on its outside edge . and the tensioner was warped (i had a spare)
So we washed the front of the motor and i managed a patch on the lower belt cover with gorilla super glue and some appropriate gauge plastic.
With all new belts and the ignition in the neighborhood of being able to be compensated by the computer, she was feeling much better.
Then my wife had a flat on the fwy, and for some reason it would not start, as it was being hauled up on the flatbed the driver reached in and turned it on, voila it ran , don't know why. So I drove the car for the next three day first two days she was o.k., the third day as i was pulling into work I could feel the throttle response get sluggish but i was there and didn't have time to fuss with it.
After work on the way home she stopped and refused to start.
Towed hone, went to the pick-a-part Saturday, and got newish Cam gear, intermediate gear,lower belt pulley, tensioner, assorted nuts and bolts and the replacement timing covers and back plate..
I redid the timing belt, and everything went back together clickety click.
But it won't start.
I put my run forever f/p relay in the console and pulled the return line from the FPR and there was gas aplenty (or so it looked). I pull the #11 fuse and I can hear the main pump load up. and I can hear the main pump run when I stick my head under the car and it sounds smooth and happy.
I replaced the cap and rotor on general principal, plugs were new three months ago passeing smog and looked clean ad no change in the gap when I pulled them prior to doing the timing belt.
I have a gizmo I bought from Harbor fright, that attaches to the spark plug wire and lites up when it gets spark from the coil. Compression is 190 across the board, and i have pretty much stopped there, for lack of any more inspirations.
all thoughts, suggestions and ideas are welcome

 

The first thing that comes to mind with a no start is the Hall effect sensor in the distributor. It detects crank angle and the computer uses that to determine engine speed and timing. They seem to start to fail intermittently a little before they completely fail. I have seen them fail once and it's final. If you can find a wrecked 740 or 760 (from 85 to 87 non-turbo or to 89 if turbo) in a junk yard, you can pull the whole distributor to get the hall effect sensor. It the part of the distributor that's hidden beneath the shield under the rotor. Later red blocks use a flywheel pickup, so there is no sensor in the distributor. The reason i suggest a wrecked car is you can be a little more sure that a failing hall effect sensor is probably not why it ended up in the junk yard to begin with.

Also when the car fails to start, look at the tach and see if it registers anything while cranking. If it shows nothing, you know it's not detecting any engine movement. Volvo has some sort of convoluted test that you can probe a few points on the ignition computer and turn the engine by hand (key on, coil unplugged) to see the hall sensor switch between 0 and 5 volts. The hardest part is probing the contacts.

The car being an 87 should have never had a round tooth timing belt sprocket. That's more proof to your earlier statement of the previous owner's neglect.

It sounds like gas should be available with your tests, so if the hall sensor is not it, I'd start diving into determining whether or not you have spark.

Good luck.

 

compression, gas, and spark.

your tester says you have spark, so lets verify you're getting injection.... much like that spark plug tester, there's a thing called a 'noid' light you plug into the injectors, and it lights up when they are fired.