1991 C3500, 454 TBI, A/T, CC Dually... eng. WILL start if you pour fuel into throttle body (yeah, I know), fuel press. to TBI is good (both F/P's ok), obviously spark is ok, I re- built TBI and checked injectors= ok... replaced some mice chewed wires (engine ran with these wires bad, then stopped running BEFORE I repaired them), no "Check Eng." light when key is turned on/ eng. not running, cannot get codes because of this--- bad ECM or...? and yes, I SEARCHED! I need my tow rig back!!

 

The oil pressure sender is in the fuel circuit. I would check that.

 

Ah, but if the eng. does run when fuel is poured down T/B, would that not eliminate the oil press. sw. as the culprit? I will, however, check it. I know that that the injectors just won't..., um..., open at all when trying to start. I'll be checking on the switch tomorrow and post results. Thanks! -John

 

O/P sw. checks out fine... still at a loss... gonna TRY another ECU JUST to see if it will change anything- none available in local junkyards so will be using one for a 350 (yes, I know it won't run RIGHT, but will at least clue me as to whether it is the ECU or not), in theory it should at least allow it to start, given that all sensors are the same between them, just the injectors (sizing) and programming are different, plug ins are all the same...

 

Does that truck have a pressure regulator up on top by the throttle body anywhere? Might be your culprit.

 

Yes, but was part of the TBI rebuild... the regulator is a part of the TBI unit, now I'm chasing down wiring gremlins...

 

Does your truck only do this when it is hot or all the time. My tbi 350 wont hardly start when it's hot. If this is your problem let me know because I need a fix too.

 

Nope.. all the time. Recent development.