Injectors not pulsing when starting.

[89Fleetside]

I'm sure this has been covered, and I have read the posts on it, but still need some feedback. Bought a 95 OBS Single Cab Fleetside Silverado with the 5.7 TBI. Decided that a TBI cleaning was in order, so sprayed some carb/injector cleaner with it still on the manifold. Next day noticed that it didn't want to start. Got some starting fluid and eventually it fired up after about a dozen tries, and would restart easily if not shut off for an extended period, but would have the same hard starting if left for a while, and had to use starter fluid to get it going. Thought that maybe the carb cleaner caused an issue with the TBI, so rebuilt it with new gaskets, injectors, new idle control valve, MAP sensor, and EGR. Can't get the injectors to pulse when cranking. Injectors click with 9v test battery. Fuel is getting to TBI. Any insight into the most plausible issue would be helpful.

 

[PlayingWithTBI]

Check your TPS to see if it's ~0.5V at KOEO and smoothly goes up to 4.5V+ at WOT. If the PCM sees >1+V when trying to start, it'll think you're flooded and will shut off fuel.

Another guess is your ICM which sends DRPs (Distributor Reference Pulses) to the PCM which will ground the injectors to make them fire accordingly.

 

[Schurkey]

hard starting if left for a while, and had to use starter fluid to get it going... ...Can't get the injectors to pulse when cranking. Injectors click with 9v test battery. Fuel is getting to TBI.

What is the fuel pressure when cranking and it won't start?

When cranking, do you have spark when there's no fuel spray? No spark and no fuel spray often means distributor problems--pickup coil, magnet, module, maybe wire harness between distributor and ECM.

 

[89Fleetside]

What is the fuel pressure when cranking and it won't start?

When cranking, do you have spark when there's no fuel spray? No spark and no fuel spray often means distributor problems--pickup coil, magnet, module, maybe wire harness between distributor and ECM.

There is spark as the engine will briefly fire with starting fluid. Just won't run as there is no fuel pulsing out of the injectors. There is fuel getting to the TBI. When I do the 9v battery test on the injectors it streams out. Not sure of the pressure though, although that wouldn't be my first assumption as the truck ran fine before the cleaning.

Check your TPS to see if it's ~0.5V at KOEO and smoothly goes up to 4.5V+ at WOT. If the PCM sees >1+V when trying to start, it'll think you're flooded and will shut off fuel.

Another guess is your ICM which sends DRPs (Distributor Reference Pulses) to the PCM which will ground the injectors to make them fire accordingly.

I will give that a shot as this seems the most likely culprit at this time. Do you think it's possible that the cleaner affected the TPS on the first cleaning? Maybe I should go ahead and replace it as it has over 100k on it.

 

[Donald Mitchell]

I have cleaned mine multiple times with carb cleaner over the last 20 yr and it still runs fine. You don't want to use it on an Idle air control valve.