10-22-2019, 05:55 PM | #197 | |
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Key in, turn it, fuel pump primes, gas pedal down 5-10%, turn key to crank, starter engages, motor spins. Then one of four things happens: 1- engine spins with no other reaction. 2- engine spins and starter kicks back. 3- engine starts and runs on fewer than 8 cylinders, idles low, won't stay running without accelerator input, runs rich. 4- engine runs great. No indication what is going to do until you turn the key. Sometimes it starts perfect after cranking for 2 seconds. Sometimes it takes 15 tries to get it to start and run well. Engine temp seems to have no effect. My tables have been all over the place trying to find something that works better than others. Nothing seems to make a significant difference. It occurred to me that it's possible for vapor or an air bubble to block fuel getting to the injectors, which a return system would fix. I don't know what else to do |
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10-22-2019, 06:00 PM | #198 | |
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10-23-2019, 02:02 AM | #199 | |
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When “1” occurs can you verify that you’re getting spark? When “2” occurs does the engine seem like it was just about to start? It’s tough to diagnose without being there to experience it. With these four different things happening and one of them being #4 that the engine runs great sometimes, I’d suspect a power supply or ground problem, bad connection somewhere or possibly a faulty sensor or ecu. |
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10-23-2019, 07:34 AM | #200 | |
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Sometimes it starts after a kick back, sometimes I have to stop cranking because of how bad it is. Battery is oversized, starter cables oversized, engine harness grounds were grounded to the engine now have a cable straight to the battery, starter has its own ground, 2 extra engine grounds+1 transmission ground. Voltage dips momentarily to 10V or less on crank initiation but comes back up right away. |
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10-23-2019, 09:23 AM | #201 |
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The voltage dip on cranking - you are measuring that with a gauge or see it in a log file?
It sure sounds like something in your ECM has an intermittent connection. |
10-23-2019, 09:45 AM | #202 |
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10-23-2019, 09:52 AM | #203 |
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Right, so the ECM sees DC voltage basically disappear. If you put a meter on a 12v signal while cranking and the charging system is working correctly I would not expect it to drop to even 11v. If it does it sounds like you have a battery connection issue. If it doesn't you have a power connection issue to the ECM.
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10-23-2019, 10:06 AM | #204 | |
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I briefly tried powering the ECU from a separate battery. It no longer displayed the voltage drop, but it didn't start any better |
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10-23-2019, 10:07 AM | #205 |
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I wouldn't worry too much about voltage drop, it is quite normal. My starter would draw around 200amp and drop to roughly 10.5 or something, but the cranking ability did not suffer. UNLESS you have a specific ECM that does not have a wide operating voltage range...for say 11.8-14.2 and you are dropping to 10, but that would encounter different characteristics in my experience.
I agree with toast on the ECM connections. And in my experience fuel starvation/air would not be intermittent like this. Two easy electrical tests to try... Try starting it in complete darkness and look for any sparks around electrical connections...sparks = poor connections. Second, after several starting attempts, feel the connections, hot connection = poor connection. Usually intermittent issues like this are electrical. My last LS build was plagued with nuisances and I ended up pulling the fuel rails off to test the injectors, verified each coil was firing, put a temp gun on each cylinder's header tube to see what was the cold one, etc. Nearly ALL of my issues were sorted out with a proper tune surprisingly. |
10-23-2019, 10:09 AM | #206 |
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This worries me. If you are blindly changing tables without knowing how to check the results, then you are shooting blind my friend. Throw that hydra thing in the trash and put an OEM computer in it.
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10-23-2019, 10:15 AM | #207 |
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I would expect some change though. I've considered changing computers but that's a pretty big investment. If I could test it for free I'd be all about it
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10-23-2019, 10:22 AM | #208 |
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10-23-2019, 10:45 AM | #209 |
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I can try, there is another guy on here using an LS1 with the Hydra unit. He said he had no problems with the tune provided by Element Tuning though. I'll see if I can get it from him
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10-23-2019, 10:59 AM | #210 |
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