I have a 93 Chevy G20 VAN G20 with a 4.3L engine that has TBI my van starts and runs for a few days. Then it will not start after sitting for a day or two it starts again and runs fine. What could be the possible cause? The fuel pump&fuel filter are working fine but the injectors are not spraying.c

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

Ignition module. I know you said the injectors won't spray. The computer gets the signal from the module to fire the injectors. Replace the ignition module.