Tataocb
Newbie
I bought a 97 C1500 with a 305 with 160k miles a couple months ago. It had a code for running rich and multiple misfires. I replaced O2 sensors, plugs, wires, dist rotor and cap and still got the code. The truck would stumble a bit when idling and have a hard time starting when hot, but was driveable. For example if I drove 15 min to the store, went in, came back out 10 min later, it would take a bit of cranking before it started. I would get the multiple misfire code and at one point got a cyl 5 misfire code.
I plugged in a Bluetooth odb2 scanner and looked at fuel trim on my iPad and short term was at -30 on both banks. Long term was about -17. So I decided to replace the injectors with an MPFI system. When I took off the upper intake it looked like the regulator was bad because the runner right below it looked clean while the rest had carbon buildup. I installed the new MPFI spider, reinstalled everything and it fired up fine. I had it running for a couple of min and went inside to get the iPad. When I came out the engine had shut off on its own.
I tried cranking but it would not crank. I spun the engine manually and it was a bit hard to turn, but got it turning. Then tried to start again and it cranked for 2 seconds, then came to a stop and would not crank anymore so I thought it was hydrolocked.
I took out all the spark plugs and spun the engine by hand and fuel came pouring out of cyl 5. The spark plug was wet as well. I then primed the system a few times, turned by hand again and got the same result, fuel poured out of the cyl.
I then unplugged the master injector connector (big single plug that goes to the spider) to check if any of the wiring was going to ground, but it seems that is not the case. I removed the fuel pump relay and turned the switch to On when I did the test. Each injector connector has two pins, for each pair, only one pin lights up the test light which is connected to battery +. So that leads me to believe the signal it gets from the ECM is correct.
With the master injector connector still unplugged, I put the fuel relay back in and primed the system a few times. I spun the engine by hand and fuel poured out again.
That leads me to believe the new injector is stuck open because with the big connector unplugged, it is not getting a signal from the ECM, and yet when I prime the system, it still dumps the fuel into the cylinder.
I was pretty set on thinking it was a bad ECM or bad wiring going to cyl 5 since even with the old/stock injectors, it threw a cyl 5 misfire code. I thought maybe the amount of fuel it dumped was just not enough to hydrolock the engine, because I was still able to drive the truck. But the fact that it dumps fuel with the master injector plug disconnected seems to point to a bad injector.
I wanted to get some opinions before going back and removing the upper intake again since it is a bit time consuming. Are there any other tests I should run to confirm/diagnose?
I plugged in a Bluetooth odb2 scanner and looked at fuel trim on my iPad and short term was at -30 on both banks. Long term was about -17. So I decided to replace the injectors with an MPFI system. When I took off the upper intake it looked like the regulator was bad because the runner right below it looked clean while the rest had carbon buildup. I installed the new MPFI spider, reinstalled everything and it fired up fine. I had it running for a couple of min and went inside to get the iPad. When I came out the engine had shut off on its own.
I tried cranking but it would not crank. I spun the engine manually and it was a bit hard to turn, but got it turning. Then tried to start again and it cranked for 2 seconds, then came to a stop and would not crank anymore so I thought it was hydrolocked.
I took out all the spark plugs and spun the engine by hand and fuel came pouring out of cyl 5. The spark plug was wet as well. I then primed the system a few times, turned by hand again and got the same result, fuel poured out of the cyl.
I then unplugged the master injector connector (big single plug that goes to the spider) to check if any of the wiring was going to ground, but it seems that is not the case. I removed the fuel pump relay and turned the switch to On when I did the test. Each injector connector has two pins, for each pair, only one pin lights up the test light which is connected to battery +. So that leads me to believe the signal it gets from the ECM is correct.
With the master injector connector still unplugged, I put the fuel relay back in and primed the system a few times. I spun the engine by hand and fuel poured out again.
That leads me to believe the new injector is stuck open because with the big connector unplugged, it is not getting a signal from the ECM, and yet when I prime the system, it still dumps the fuel into the cylinder.
I was pretty set on thinking it was a bad ECM or bad wiring going to cyl 5 since even with the old/stock injectors, it threw a cyl 5 misfire code. I thought maybe the amount of fuel it dumped was just not enough to hydrolock the engine, because I was still able to drive the truck. But the fact that it dumps fuel with the master injector plug disconnected seems to point to a bad injector.
I wanted to get some opinions before going back and removing the upper intake again since it is a bit time consuming. Are there any other tests I should run to confirm/diagnose?