Chevy 2500HD No Start, No Spark, No Fuel, Cranks OK
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Date: 2020-08-05
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Comments and reviews: 10
Bryan
No need to be embarrassed. If you are comfortable, you aren't learning. FWIW, I did catch that it wasn't going all the way to ground, but I kind of shrugged it off consciously. I figured that the input to the ecm was AC coupled and so it didn't need to go all the way down.
What you are looking at wasn't even possible a decade earlier. Silicon will get better. Software will get better. Sensors will get better. Diagnostics will get better.
It would be delightful if manufacturers provided reference waveforms that were easily accessible.
Back in the early days, silicon (and especially memory) came at a premium. An earthquake in Japan could (and did) cause global memory shortages. This is probably why they started using P codes and lookup tables, because they save memory. Today though, there are graphic displays and memory is cheap and easy. It really bugs the hell out of me that we are still wrestling with 8000 scan tools when the information could be presented in plain English/Spanish/French/Whatever right on the dash.
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No need to be embarrassed. If you are comfortable, you aren't learning. FWIW, I did catch that it wasn't going all the way to ground, but I kind of shrugged it off consciously. I figured that the input to the ecm was AC coupled and so it didn't need to go all the way down.
What you are looking at wasn't even possible a decade earlier. Silicon will get better. Software will get better. Sensors will get better. Diagnostics will get better.
It would be delightful if manufacturers provided reference waveforms that were easily accessible.
Back in the early days, silicon (and especially memory) came at a premium. An earthquake in Japan could (and did) cause global memory shortages. This is probably why they started using P codes and lookup tables, because they save memory. Today though, there are graphic displays and memory is cheap and easy. It really bugs the hell out of me that we are still wrestling with 8000 scan tools when the information could be presented in plain English/Spanish/French/Whatever right on the dash.
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David
Hey, i have this problem, and im good with cars, i have somebody else do my pogramming i dont have the equipment besides a otc scanner. I have a 2005 silverado 1500 4x4 auto. Good truck, good shape, so i decided to put a new engine in it after 270000 when oil pressure dropped due to cam bearings. On the new engine, its a gen iii, i put in a new ls9 cam, ls3 front cover with cam sensor, wire extention harness, pin A&C swapped, new crank sensor, nv4500, np241 manual, it only cranks, no start, doesnt even hit, got injector power, got coil power, but no fuel inj pulse, no ignition, fuel pump runs for a sec on key on, no codes, i even plugged tranny and transfer back in, double checked grounds and wires several times. Old engine ran just fine before swap. Everything intake and up is original, not a cali truck. Any ideas? Could i have done something to trigger the vats?
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Hey, i have this problem, and im good with cars, i have somebody else do my pogramming i dont have the equipment besides a otc scanner. I have a 2005 silverado 1500 4x4 auto. Good truck, good shape, so i decided to put a new engine in it after 270000 when oil pressure dropped due to cam bearings. On the new engine, its a gen iii, i put in a new ls9 cam, ls3 front cover with cam sensor, wire extention harness, pin A&C swapped, new crank sensor, nv4500, np241 manual, it only cranks, no start, doesnt even hit, got injector power, got coil power, but no fuel inj pulse, no ignition, fuel pump runs for a sec on key on, no codes, i even plugged tranny and transfer back in, double checked grounds and wires several times. Old engine ran just fine before swap. Everything intake and up is original, not a cali truck. Any ideas? Could i have done something to trigger the vats?
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Robert
I don't know if any of this will make you feel better, but:
It would not be obvious to me that a square wave has to go all the way to zero. In many (if not most) such applications, the actual voltage isn't important, only the detection of a change from high (=1) state to low state (=0, and width of each state. Put differently, the specs I've seen are in terms of high us any voltage above X and low is any voltage below Y. So, not only did I not see the too high low, I wouldn't have looked for it.
Wholly apart from that, I wish I could say I never looked at data that looked like what I was expecting but failed to notice a non-obvious discrepancy. Jeekers, I'd settle for being able to say I've only made that mistake once. But I can't do either.
Maybe now, thanks to you, I'll be more careful.
reply
I don't know if any of this will make you feel better, but:
It would not be obvious to me that a square wave has to go all the way to zero. In many (if not most) such applications, the actual voltage isn't important, only the detection of a change from high (=1) state to low state (=0, and width of each state. Put differently, the specs I've seen are in terms of high us any voltage above X and low is any voltage below Y. So, not only did I not see the too high low, I wouldn't have looked for it.
Wholly apart from that, I wish I could say I never looked at data that looked like what I was expecting but failed to notice a non-obvious discrepancy. Jeekers, I'd settle for being able to say I've only made that mistake once. But I can't do either.
Maybe now, thanks to you, I'll be more careful.
reply
Dave
I know this video is a little old but I'm curious if you had to do the GM Crank position relearn thingy on this with your scan tool and all. I have a 2003 that has crank but no start and I have no spark also. I dont have a fancy scan tool or a scan tool at all but the truck has been sitting for a while had to get the bad gas out of tank and I replaced fuel pump and fuel filter but it still didn't crank so I was going to do this sensor next. Low and behold you did a video on it which is awesome I some how knew you did. But all I've read up on is after I install the new sensor I have to run a relearn on it. just curious if you have ran into an issue with having to relearn any of these after installing?
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I know this video is a little old but I'm curious if you had to do the GM Crank position relearn thingy on this with your scan tool and all. I have a 2003 that has crank but no start and I have no spark also. I dont have a fancy scan tool or a scan tool at all but the truck has been sitting for a while had to get the bad gas out of tank and I replaced fuel pump and fuel filter but it still didn't crank so I was going to do this sensor next. Low and behold you did a video on it which is awesome I some how knew you did. But all I've read up on is after I install the new sensor I have to run a relearn on it. just curious if you have ran into an issue with having to relearn any of these after installing?
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Kayena
Hey south main auto i got a 98 chevy blazer lt, with a rough iddle, fuel pump, fuel filter new fuel spider injectors, intake manifold gasket, new ac delco spark plugs, wires, cap and rotor as well distributor shaft, every single sensor you can think off even pcv valve and still runs rough backfires at speed, i think is the coil cus i got it from the junkyard, NO codes do, no compression issues just a bad cat and it was cut it places, am tempting to take it to you to find out if my engine is old or am i missing something?
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Hey south main auto i got a 98 chevy blazer lt, with a rough iddle, fuel pump, fuel filter new fuel spider injectors, intake manifold gasket, new ac delco spark plugs, wires, cap and rotor as well distributor shaft, every single sensor you can think off even pcv valve and still runs rough backfires at speed, i think is the coil cus i got it from the junkyard, NO codes do, no compression issues just a bad cat and it was cut it places, am tempting to take it to you to find out if my engine is old or am i missing something?
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John
Good info thanks. At first glance like you said an obvious crank signal but values were off probably saturated with oil didnt help. And maybe could be caused by temperature. I have had a few mind bogglers where a vehicle wouldnt get injector pulse or spark during the heat of the day but would always start in the mornings. Like it was demonic. I ended up just replacing crank sensor and got lucky but took a few hours more than i wanted to spend on the car. Thanks again.
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Good info thanks. At first glance like you said an obvious crank signal but values were off probably saturated with oil didnt help. And maybe could be caused by temperature. I have had a few mind bogglers where a vehicle wouldnt get injector pulse or spark during the heat of the day but would always start in the mornings. Like it was demonic. I ended up just replacing crank sensor and got lucky but took a few hours more than i wanted to spend on the car. Thanks again.
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Timothy
Thanks for doing this video, it lead me directly to a bad crank sensor on a 1500 with a 4. 8 I'm fixing for a friend, It helped to see the crank sensor sits high and pulls low, the one I was working on was low at all times, swapped and started right away. Literally 1 hour to get it started after sitting untouched for 3 years by the last moron.
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Thanks for doing this video, it lead me directly to a bad crank sensor on a 1500 with a 4. 8 I'm fixing for a friend, It helped to see the crank sensor sits high and pulls low, the one I was working on was low at all times, swapped and started right away. Literally 1 hour to get it started after sitting untouched for 3 years by the last moron.
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John
For what its worth. When you came off the high side of your scope and grabed a wrench to bump the engine over just a bit. I think i would have turned off the ignition. You did say it was in the run position. And i have seen some strange things happen in engine compartments. Better safe than sorry.
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For what its worth. When you came off the high side of your scope and grabed a wrench to bump the engine over just a bit. I think i would have turned off the ignition. You did say it was in the run position. And i have seen some strange things happen in engine compartments. Better safe than sorry.
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TS
18: 20 Look in the background at the upturned spout setting in the funnel on the wall. Doesn't it look like one of those stone faces on Easter Island? Could they have really been an island of ancient mechanics, servicing the vehicles the aliens used to build the pyramids?
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18: 20 Look in the background at the upturned spout setting in the funnel on the wall. Doesn't it look like one of those stone faces on Easter Island? Could they have really been an island of ancient mechanics, servicing the vehicles the aliens used to build the pyramids?
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MOPEDMAN28
PLEASE HELP ME! I have a 02 chevy saburban. Cranks ok. No fuel. No spark. And no communication at the obd port.
I watched this video and got so excited. Went right out and put in a new crank sensor. With no success. Please help me!
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PLEASE HELP ME! I have a 02 chevy saburban. Cranks ok. No fuel. No spark. And no communication at the obd port.
I watched this video and got so excited. Went right out and put in a new crank sensor. With no success. Please help me!
reply
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