93 TBI not spraying fuel during crank

[kevinvinv]

I ran into a weird problem (to me). My buddy has a 93 or 94 TBI on a 454 basically stock setup in a motor home.He developed this problem where the injectors won't spray during cranking but if you get it to fire using starting fluid or drizzling fuel into the TB-- then it will fire and the injectors will start spraying and the engine runs just fine from then on.Anyone see this before? Thanks!!!

[kacy]

try disconnecting the tps then crank it.

[dave w]

I've not seen that exact problem before. The ignition module tells the computer the engine is being started, then when engine starts running at about 400 PRM's the computer takes control full control. I wonder if there might be a problem with the ignition module bypass circuit??? dave w

[kacy]

I had a 93 that wouldn't spray during cranking, apparently my tps was telling ecm WOT creating clear flood while cranking.

[uncabob]

I ran into a weird problem (to me). My buddy has a 93 or 94 TBI on a 454 basically stock setup in a motor home.He developed this problem where the injectors won't spray during cranking but if you get it to fire using starting fluid or drizzling fuel into the TB-- then it will fire and the injectors will start spraying and the engine runs just fine from then on.Anyone see this before? Thanks!!! Can you tell if fuel pressure is coming up when you turn the key on with engine off? It sounds like a fuel pump relay circuit problem. Once it is running the oil pressure sensor switch takes over and keeps the fuel pump on. Good luck and Happy New Year. Bob

[kevinvinv]

thanks all- I am feeding this info to my buddy... let's see what he finds! You guys are great!

[uncabob]

thanks all- I am feeding this info to my buddy... let's see what he finds! You guys are great!Tell him that he should hear the fuel pump come on for at least 2 seconds. (As long as there isn't too much background noise.) Bob

[jeff5may]

I ran into a weird problem (to me). My buddy has a 93 or 94 TBI on a 454 basically stock setup in a motor home.He developed this problem where the injectors won't spray during cranking but if you get it to fire using starting fluid or drizzling fuel into the TB-- then it will fire and the injectors will start spraying and the engine runs just fine from then on.Anyone see this before? Thanks!!!I had this problem with an 88 s10. The thing would start up if you cranked the engine long enough to build up oil pressure. If you fed it fuel or the fuel pump relay was jumped out, the truck started up right away. It ended up being the ecm. I swapped computers with a buddy's truck and the. problem followed the computer. When you switch on the ignition, the computer sends a priming pulse to the fuel pump for a few seconds. Rather than swap out the ecm, I rigged up a one-shot timer to pulse the fuel pump relay. Still working many years later.

[uncabob]

I had this problem with an 88 s10. The thing would start up if you cranked the engine long enough to build up oil pressure. If you fed it fuel or the fuel pump relay was jumped out, the truck started up right away. It ended up being the ecm. I swapped computers with a buddy's truck and the. problem followed the computer. When you switch on the ignition, the computer sends a priming pulse to the fuel pump for a few seconds. Rather than swap out the ecm, I rigged up a one-shot timer to pulse the fuel pump relay. Still working many years later.If there is a test point connector for the fuel pump relay circuit (a single wire connector hanging loose) you can check it for voltage when the key is turned on. Some are set up to apply 12 volts to test the pump. If the ECM is the problem you can use that connector to get around it. I'd check the relay first though. Bob