Hoping someone can help me track down the issue with my fuel injectors...appears to be something electrical and I'm at my wits end.

The problem is the engine suddenly started running super rough and stalling. I replaced the fuel injectors (free parts car is available) and still the same problem. Codes came on at one point that said open circuit on 5 of the 6 injectors (they haven't come back on after clearing codes and resetting ecu, even though the problem hasn't resolved). When I take out the injectors one by one nothing much happens except cylinder 5 (it stalls when that one is removed). So I figured it must be a power to the harness problem, but that hasn't panned out either. Below are results from checks I did. My guess is there must be something going on at the pcm/ecu side of things but I don't know what diagnostics to try. Any help/advice would be much appreciated.

0 volts at hot wires on connectors from the wiring harness when ignition is in on position. Seems like that's saying there's no power getting to injectors. They should be reading 12v.

There's continuity between the hot wires on connectors from the harness and chassis ground, resistance is 2.8 ohms. It's the same with ignition on or off. Does that indicate a short? I would think there shouldn't be continuity on a hot wire. Maybe I'm misunderstanding this part though.

Test light flashes for all 6 connectors at the harness when the engine is cranked. The test light was connected to the hot and ground wires of the connectors. So apparently power IS getting to injectors somehow when the engine runs, and the pulsing ground is working. I'm not able to see how many volts are coming through when the engine is cranked and I'm thinking maybe low volts to the injectors is where the problem lies. Or a short on the hotwires or pcm/ecu somehow?

There's ontinuity between fuel injector prongs, resistances are all around 12.0 . So fuel injectors.are good.

All wires in wiring harness along engine look to be in good shape.

 

I think you may be chasing the problem in the wrong spot. It seems like you may have jumped to a conclusion that the injectors were the issue.

Clear the codes and see if anything else comes back. Take the distributor cap off and look at the contacts. Pull the spark plugs out and take a look at them. Run a compression test on the engine.

FYI, the injectors will have 12v on one wire when the key is on, and the other wire will have the ground pulsed to it when cranking or running.

 

Thanks for the suggestions. 100% agree I jumped the gun on assuming bad injectors. The problem started after driving way below empty and then filling up the tank so I figured maybe gunk got into the injectors. And after 450k+ they probably needed changing/cleaning anyways and the parts were free...but such a waste of time going down that road.

The codes haven't come back on after being cleared, but the problem is still severe. They didn't come on for the longest time after the problem started as well, so I really don't put much faith in them. I did check distributor cap and the contacts were a mess. I swapped it for the one from the parts car which was much better and I cleaned the contacts while I was at it. Didn't pull the spark plugs yet but that's a good idea. I don't have equipment to do compression tests unfortunately.

I made a mistake typing up my explanation. I would've grounded the test light to the wiring harness because you're right, the hot wire is always hot and the system pulses the ground to make the injectors spray. So if I grounded to the chassis the light wouldn't have flashed when cranking the engine. It did flash though, for all 6 connectors, which says to me that at least some power is reaching the injectors. But yet somehow there are 0v on both wires when the key is on, even though one (the hotwire) should be reading 12v.

Should the hotwires be reading continuity when the key is on? That I don't understand. There's 0v on the hotwires but 2.8 ohms when grounded to chassis. Same thing whether the key is on or off. There's no continuity for the ground wire with the key on but not cranking which is what would be expected.

 

If the test light is lighting up, you have sufficient power to run the injectors. Have you checked the fuel pressure by chance?

Running the tank low does not cause trash to get sucked up. The fuel pump suction is already at the bottom of the tank. Also, there's a strainer at the bottom of the pump. What I would wonder about, though, is if something is up with that gas you pumped in, since it all started after filling up.

 

No, I haven't checked fuel pressure yet. Good suggestion. If there's one thing this is proving it's that I need more sophisticated diagnostic equipment. I wondered about bad gas too, I got about 3 blocks from the gas station when the problem started. I checked in with them just to be sure there wasn't something going on. I even wondered if maybe somehow it was filled up with diesel even though I know the nozzles are different sizes. It's cheap gas but there are a bajillion cars filling up there always, so I figure if it was a gas problem there'd have been a line of cars on the side of the road with problems too. After learning more about fuel injector problems and thinking about the day, I now believe there was likely a significant reduction of mpg before the engine acted up and I just didn't notice it.

Do you have any thoughts about why my hotwires are showing 0v when ignition is on? It's driving me up the wall not knowing why.