engine is on firing on three cylinders. Just rebuilt distributor tonight still not firing on all cylinders. It has new ECM, Injectors, fuel pump, fuel line. Has about 25 miles on a new ecm and this problem started. I bench tested two injectors and work ok. Shot gas in the thottle body starts firing on all cylinders. Fuel pressure 43lbs when running. Jumper one injector to 12 volts will not fire cylinder. Shut car off watch fuel pressure gauge drop when jumpered injector. Did have a problem a couple weeks back with water in the fuel but drained tank and ran fine for 200 miles.

 

Remove injectors found 6 would not spray only two would barely spray.
Found fine rust particles cleaned with mineral spirts. Fuel tank has few rust spots going to use fuel tank liner to correct problem. This car has all new fuel line, injectors, fuel pump. Didnot think the little rust in the tank would hurt anything. Fuel fuel must be letting the small particles get by.

 

Glad you found your problem... did you figure out that the ECM fires the injectors by providing a ground, not 12 V. I found out when MY TPI was firing on only one bank... my son had snagged on of the 12V leads with his foot and pulled it out, so only had 12V to half of the injectors. (PO converted this '86 carb'ed V8 to TPI with a '85 setup. Kid did a mediocre rewiring job.)
Tony