Starts and dies after a few seconds
Starts and dies after a few seconds Hi all,
I'm trying to sort out a problem. I have a GMPP engine controller with a 5.3L in a Porsche 944. This is a Gen IV setup. I started it the first time, and it ran great for 2 seconds, very smooth it seemed. Then it died out. The second time, I unplugged the MAF, thinking maybe the MAF was an older one (03 Corvette) that wouldn't work with the Gen IV controller. I attempted to use the throttle to hold the engine up, but it still died after a few seconds. After cranking again with just the MAP, it will not fire. But I can hear the fuel pump running.
I know it sounds like a VATS issue, but this is a GMPP controller, so it shouldn't be a VATS thing... Any other thoughts?
I'm trying to sort out a problem. I have a GMPP engine controller with a 5.3L in a Porsche 944. This is a Gen IV setup. I started it the first time, and it ran great for 2 seconds, very smooth it seemed. Then it died out. The second time, I unplugged the MAF, thinking maybe the MAF was an older one (03 Corvette) that wouldn't work with the Gen IV controller. I attempted to use the throttle to hold the engine up, but it still died after a few seconds. After cranking again with just the MAP, it will not fire. But I can hear the fuel pump running.
I know it sounds like a VATS issue, but this is a GMPP controller, so it shouldn't be a VATS thing... Any other thoughts?
Last edited by superman22x; Jul 18, 2016 at 06:38 PM.
I ordered what I know is the correct MAF (card style) for the GMPP Cals, so I will try that out. It's possible that since this is a brand new controller, and there are no fuel trim learns, that with the IAT and MAF unplugged, it just doesn't run.
Another update. I cut the wires to my old MAF (new one isn't here yet) so I could leave the IAT plugged in. Tried to start again, but no luck. I checked codes, and the only one is a P0512 for start circuit fault. I have my starter wired directly into the Porsche switch, so the ECU never gets a starter signal.
After I start it once and it then dies out, if I crank again, it will not start until I unplug the battery. I checked spark in this condition, and there is no spark. I'm not sure what would cause the no spark condition?
After I start it once and it then dies out, if I crank again, it will not start until I unplug the battery. I checked spark in this condition, and there is no spark. I'm not sure what would cause the no spark condition?
Another update... Found out J1-10 is supposed to have power at the ECU (E67) for GMPP engines only. Fixed that. Didn't seem to make a difference.
Then I unplugged the cam sensor for no particular reason, tried to crank, and no start. Plugged the cam sensor back in, and it fired right up and ran decent. Stayed running too. Only issue is a popping into the intake. Could be because of LS1 injectors on a stock LC9 tune. And no MAF. Or 02 sensors yet.
Then I unplugged the cam sensor for no particular reason, tried to crank, and no start. Plugged the cam sensor back in, and it fired right up and ran decent. Stayed running too. Only issue is a popping into the intake. Could be because of LS1 injectors on a stock LC9 tune. And no MAF. Or 02 sensors yet.
That last post of yours has quite a few things that should get sorted out asap before you try to run the motor. O2 sensors aren't necessary until the motor goes into CL but it will still make the PCM angry. Injector data is a 100% must. The only reason it's starting is that it uses completely different tables for cranking and post start. Usually 2-4 seconds. After that it uses normal fueling tables. Once up to temp it starts using the O2's. The fact that it's starting is luck. Everything about how the engine runs requires proper injector data.
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Yes, I agree, there are many things to sort out.
I thought the LC9 injectors flow around 26lb/hr, which should be pretty similar to LS1 injectors if I'm not mistaken? They are both just simple saturated signal injectors. I'm not positive about the LC9 having similar injector flow though.
As long as the MAF/02 and knock systems are functioning, it should run ok at part throttle. The odd thing is that I never got a code for the unplugged MAF...
I thought the LC9 injectors flow around 26lb/hr, which should be pretty similar to LS1 injectors if I'm not mistaken? They are both just simple saturated signal injectors. I'm not positive about the LC9 having similar injector flow though.
As long as the MAF/02 and knock systems are functioning, it should run ok at part throttle. The odd thing is that I never got a code for the unplugged MAF...
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Verdad Gallardo Well, got the new MAF in, and still same exact symptoms. I have the Torque app now as well, so I can monitor flow rates and such. I made sure all my temp sensors were reading right, and they were. The odd thing is the MAP sensor reading is 17.4 psi (~120kpa) at ambient. I measured voltage and it is 4.80v (5.05v to the sensor).
I thought this might be a scaling issue in the Torque app, but I think it's a sensor problem. I plugged the OBD tool in a newer GM vehicle and it read 14.4psi, like it should. So this map sensor I have from an LS6 (16212460) must not be compatible with the GMPP ECM. I'm not sure what MAP sensor to use though. I did try another MAP sensor I had in the garage, same part number, and got the exact same readings. I also verified that it worked by putting some vacuum on it and reading the value in Torque. It changes values, but it's off by a decent amount.
Can someone confirm the flowrate of the LC9 injectors? If they are much higher than I am estimating, than that would be a much bigger problem than I had originally thought.
EDIT: It seems that the new MAP sensors for LS3 and other modern truck engines are all ~128kpa sensors, which would explain why when using an LS6 map sensor, I was getting a reading of ~120kpa. Ordered an LS3 map sensor, so that should help. I'll just need to find a way to mount it in the LS2 intake I have. Are LS2 map sensors 128kpa range as well?
Tomorrow I can try running with just the MAF plugged in I guess.
I thought this might be a scaling issue in the Torque app, but I think it's a sensor problem. I plugged the OBD tool in a newer GM vehicle and it read 14.4psi, like it should. So this map sensor I have from an LS6 (16212460) must not be compatible with the GMPP ECM. I'm not sure what MAP sensor to use though. I did try another MAP sensor I had in the garage, same part number, and got the exact same readings. I also verified that it worked by putting some vacuum on it and reading the value in Torque. It changes values, but it's off by a decent amount.
Can someone confirm the flowrate of the LC9 injectors? If they are much higher than I am estimating, than that would be a much bigger problem than I had originally thought.
EDIT: It seems that the new MAP sensors for LS3 and other modern truck engines are all ~128kpa sensors, which would explain why when using an LS6 map sensor, I was getting a reading of ~120kpa. Ordered an LS3 map sensor, so that should help. I'll just need to find a way to mount it in the LS2 intake I have. Are LS2 map sensors 128kpa range as well?
Tomorrow I can try running with just the MAF plugged in I guess.
Last edited by superman22x; Jul 23, 2016 at 10:30 PM.
