1990 TBI Fuel injection after engine runs and is driven around then turned off it will not start again.

If this is still TBI the issue is the air in flow valve located on the passenger side of the Throttle body. Un plug it and unscrew it . I believe it is a 7/8 wrench. Clean it with carb. cleaner and spay out the TBI and in the hole where this goes. Re install and se how it runs. Other wise its a vacuum leak. If you have a fuel injected model it may be lose of fuel pressure.

Will it start and or run with a shot of carb spray down the throttle body?

can you hear the fuel pump running?

have you checked to see if there is fuel pressure?

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

SOUND LIKE FUEL PUMP.REPLACE FUEL FILTER,CHECK FUEL PRESSURE SHOULD BE 9 -13 PSI. FOR TBI FUEL INJECTION AND 55 - 61 PSI FOR MFI MULTIPORT FUEL INJECTION SYSTEM.

check your fuel pressure if it has the CPI injection pressure should be 58-65 psi with key on engine off.If your motor has the TBI throttle bodt injection your fuel pressure should be 9-13 psi with engine running.

for tbi injector it will be around 14-20 psi...for multiport injection it will be 40-60 psi

Fuel injection needs 20-30 pound pressure to fire the injectors. Try to check pressure before filter. If its low your pump is no good. If its ok then you have pressure drop after the filter. Filter on backwards or clogged.

You first need to check the fuel pressure, an easy way to access this is to buy a can of spray starting fluid, spray it into the TBI throttle valve and if the truck starts and dies you have no fuel pressure. Replace the fuel; pump, and make sure you get the right pump, it is a low pressure system.

Make sure you are getting power to the injectors. I have the same,350 tbi. Check the fuses and relays and check the wires at the tbi to make sure one of them is not rubbed through. The injectors have to be getting intermitent power .

There are three relays all grouped together on the firewall on the passengers side. All three are related to your situated. We can eliminate one of them because you stated that the fuel pump is operating fine. Now that leaves the relay for the ECM(engine control module) this tells the injectors, cold start and run, when and how much fuel to supply and also controls ignition timing and spark advance. The third controls the AC compressor. Now I've got to remind you that I started working on fuel injection systems the day they started failing here in the US around 1972.These were such vehicles as Mercedes, Saab and Volvo. I've worked on every configuration, TBI, MPI, diesel etc.etc. I may on occasion cross one fact with another or mispronounce certain aspect of a system however, These three injectors are where you want to concentrate your efforts. With some finnesse you can swap the harnesses from one to another. If your car runs fine and your AC suddenly does not, then you know that that relay is faulty. Do this until you get your answer. Best of luck my friend, Dana

sounds real easy either a bad idle air control solenoid or more likley a blown throttle body gasket. to test fro a blown gasket, with engine running and cool spray carb cleaner or brake cleaner around base of tb were it bolts to intake. when it hits the bad area, should idle down and be normal for a second or 2. iac is possible,try this first since its so common and let me know