Died in the Heat.. (88 745T 181K)
My 88 740 wagon was purchased 5 mos. ago and I have put 14K on it since. All long road trips, oil changes of Rotella T at 2-3K, etc and it has been running flawlessly although I suspect an in tank pusher pump not working due to the nature of the main pump "singing" at 1/3 to 1/2 tank full. Today at the end of a three hour trip I cooled down for 20 mins and then drove out to eat lunch. When I came out 45 mins. later, the car started and went 1/2 block, leaned out and would only idle (stumbling and sputtering). It acts as though it has vapor locked in the 90 Degree temp. I can hear the FPR click when turning on the key, but I have never since I purchased this car heard the main pump "whirr" when turning on the key as on most of my other Volvos. I waited till this evening for cooldown, but it never started. I am going to try a full tank of gas in the morning and jumping the FPR as well as try the ignition boost relay on the fenderwell. I also have an MAF coming to try tomorrow.
Any suggestions?

Well...I checked the next day and no resistance reading from the load side of fuse No. 11 (in Tank Pump) Filled up with gas and it finally started and I limped back 170 miles with fill ups at 60 mi. intervals. Found the rubber hose from the pump had torn open and replaced the AC Fuel pump with the NAPA Carter equivalent $70. Used solid 5/16 hose and now running fine. The 90 Plus degree weather was more than the main pump could handle without flooded suction provided by the in tank unit. I had also checked the fuel pump relay(s) and both were OK. Now I get the "prime" sound when bumping the starter.
Thanks for the suggestions. (4th. pump issue in 25 yrs of Volvo's and 16 cars.)

An off the wall that happen to me. Cat converter completely blew out and clogged the exhaust. It would only idle. Once I ran the big three checks, fuel, spark, compression. Loosen the exhaust manifold and it started right up and ran.

Have you replaced your fuel filter?