So my 89 iroc with the 305 is causing me nothing but headaches now. I can start my car anytime and she runs fine but if I drive her around the block and then let her sit for 30 mins or so she won't have any fuel pressure. Today I sprayed starter fluid in the intake just to verify the issue was fuel related and she started and ran fine. Didnt die after the ether was stopped being used. I can force the fuel pump on and hear it running but no pressure is built. Fuel pump, fpr, fuel filter, coolant temp sensor, and ecm have all been replaced. I do know that 2 injectors are faulty because when I checked resistance one was at 8 ohms and the other was at 2. Would injectors cause this type of issue? Any help is appreciated. Just inherited this car from my parents who couldn't take care of it anymore

 

Yes if you have a bad winding in a injector it could cause the injector circuit to over load.
Are you sure you are loosing fuel pressure? because a bad injector could not cause that but it can cause no fuel to get to a cylinder.

 

I will double check again. Maybe I didnt have the gauge fully seated on the rail but it was def showing zero psi. That's what is confusing me because the gauge said zero and it started with ether so that sounds like I'm not getting fuel but once the ether ran out the car kept running which makes no sense to me.

 

Ok, I had to drive her 3 times today to get her to not restart for me. I do have around 40psi of pressure at the rail. So either the injectors aren't opening or maybe the vats is cutting fuel. I don't honestly know because my knowledge of these 3rd gens is minimal at best. She will crank and run for a couple of secs if I use ether but she will die right away. I sprayed ether 2 or 3 times and then she cranked and continued running. I'm lost as to what else I should do now. I have 8 injectors ordered just because I know 2 ohms on an injector is definitely not good.

 

Is the security light on? You should be able to find a injector noid light you can hook up to the system. Step one would be to know if you are loosing positive or negative. You have to do that with a good electronics grade volt meter. If I remember right positive comes from a fuel injection relay and the PCM just grounds the injector. If it was me I would replace those bad injectors they could be shorting out the system once they warm up. I am not one for throwing parts at a problem but if you have known bad injectors any manual would tell you to replace those before moving on. Would be nice to know if the engine would try to start with those two injectors unplugged..

A manual would really come in handy.

 

No security light at all. I read that the vats would trigger that light but the only light I have is the service engine light and that only comes on after its driven about a block. Speedometer doesn't work so I'm assuming that's what that issue is. Does anyone have the flow rate of stock injectors. I havent been able to find that info on the 305.

 

I have compared the flow rate of cylinder that was running lean with one that was normal on the scope but why would you need know flow rate? I can not say I have ever known or looked up the flow rate of a stock injector. If you are just trying to find injectors you should get them by application not flow rate. If you are building a motor and plan on turning it then flow rate is a key factor. If you are just replacing a stock injector on a car with a stock tune. then consistency is all that matters. Either an OEM or a rebuilt OEM is the way to go. I can only remember 3 injectors for the TBI system. The 305, the 350 and Corvette 350.

One thing this system can not do is adjust for individual injector variation. Many techs will recommend replacing all the injectors in a matched set even sending them out to verify matched flow rates. With a scope you can verify rich/lean of every cylinder. GM does not require either of those processes as they assume OEM injectors.

 

I was looking for flow rate because anything above 22 psi had info listed that they require ecm tuning to run properly. I know the ecm can adjust based on what it sees coming out of the o2 sensors but I know for certain applications you have to tune. I am changing all 8 injectors out due to at least 3 of them being far to low on resistance and the car being 33 years old lol.

 

The main thing is that the Injector match each other. Yes the O2 sensor can adjust but it adjust all 8. There is only one O2 sensor so all the ECM knows if the rich/lean of the whole engine. So lets say you have one weak injector. That cylinder runs lean. The O2 picks up the lean signal and richens up all 8 cylinders. Now you have one cylinder that is still too lean but a little better and 7 cylinders all running to rich.

So what you can do is get two identical glass containers. Pick one of the the injectors that tested good and pull any other one. Disable the ignition (that is important) now crank the engine over over for 15 seconds. compare and write it down the difference between the two. You can use just distance but weight would be more accurate assuming you verify the empty weight. Then move to another injector keeping the first good injector as part of the test. Rerunning the one known injector removes variable like getting the on/off timing perfect or fuel pressure variation.

The bad part about buying all new injector is you could easily get a bad one and be right back where you are. But if that happens you can run the balance test on the new injector. If you are thinking all the injector are weak they should not be. The ECM watches how much it leans and riches the engine. It has limits and as it nears those limits it should set a check engine lite with a lean code stored. That should happen before you can feel any drop in power.

 

That makes a lot of sense. I actually have an injector tester and cleaner machine on its way to me. I could always verify resistance on all the new injectors and then flow test them myself to ensure they all work well before I install them.