no spark on lm7, HELP!
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no spark on lm7, HELP! I did an engine swap in my 52 chevy. It's an lm7 with a painless perfect engine management system. It ran fine for a month. I started it up one day and drove about 200 yards before it started running very poorly. I turned the car back around and shut it off at my house.
I couldn't get it to start and it didn't have spark. I did all the basic trouble shooting problems. Replaced cam and crank sensor, checked to make sure all the circuits had power, etc. Still no spark.
I sent the ECM back to painless and they told me there was a trouble code for open circuit on the ignition, spark fault, code 41. also a code for low voltage to the MAP.
I just got the computer back, still no spark, and the computer doesn't have any codes in it.
I'm gonna check every wire in the engine harness this weekend for continuity and replace the MAP sensor.
Painless is trying to tell me that the issue isn't with their computer, and the only thing that can cause this is a bad coil driver. According to them "they rarely go bad" but said they have no way of checking it when I sent my computer back.
I have a silverado and was going to swap the coil packs to see if something had grounded out.
Any other advice? or am I getting jerked arounf by painless? Thanks.
I couldn't get it to start and it didn't have spark. I did all the basic trouble shooting problems. Replaced cam and crank sensor, checked to make sure all the circuits had power, etc. Still no spark.
I sent the ECM back to painless and they told me there was a trouble code for open circuit on the ignition, spark fault, code 41. also a code for low voltage to the MAP.
I just got the computer back, still no spark, and the computer doesn't have any codes in it.
I'm gonna check every wire in the engine harness this weekend for continuity and replace the MAP sensor.
Painless is trying to tell me that the issue isn't with their computer, and the only thing that can cause this is a bad coil driver. According to them "they rarely go bad" but said they have no way of checking it when I sent my computer back.
I have a silverado and was going to swap the coil packs to see if something had grounded out.
Any other advice? or am I getting jerked arounf by painless? Thanks.
Do you have injector pulses as well?
On mine, I had no spark & no inj pulse because the ground lead from the crank sensor had broken.
The 3 leads for the CKP sensor might be a place to look.
I couldn't tell you if there were any codes, I didn't check for them.
On mine, I had no spark & no inj pulse because the ground lead from the crank sensor had broken.
The 3 leads for the CKP sensor might be a place to look.
I couldn't tell you if there were any codes, I didn't check for them.
Good point on the injector pulsing question. If the injectors are not pulsing and you have no spark then it sounds like you have an issue with the crank sensor circuit. I would start with checking continuity on all three wires at the crank sensor. Also, how did Painless pull codes on a computer that was pulled out of a car?
Jon
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Jon
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It sounds like the injectors are pulsing when I cycle the key. Which wire on the crank sensor plug is for the ground? Black I assume? The car died in front of my buddys house so I can't just go outside and look at it. I swapped the crank sensor but that doesn't answer my problem. What am I looking for on the 3 CKP sensor wires? Should I see 12v or am I looking at the resistance?
I feel like I am getting a slight run around from p[ainless. They keep having me check the same things over and over. This is the first mention of checking the CKP sensor wires.
They told me the only thing they can think of is that the coil driver went bad but that only happens if you weld on the car with the ECM hooked up. Therefore I must be lying. The car was at a car show 18 hours before it died. No welding, just driving. If this doesnt fix it I'm gonna get stuck buying a new computer. The car only ran for a month...
I feel like I am getting a slight run around from p[ainless. They keep having me check the same things over and over. This is the first mention of checking the CKP sensor wires.
They told me the only thing they can think of is that the coil driver went bad but that only happens if you weld on the car with the ECM hooked up. Therefore I must be lying. The car was at a car show 18 hours before it died. No welding, just driving. If this doesnt fix it I'm gonna get stuck buying a new computer. The car only ran for a month...
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Did you have this same set up?
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it is one of those GM delphi computers thats a stand alone set up. Will that software even work? they sell software for this computer. I used to be a tech at vortech and a good frined of mine is the tuner. he has HP tuners. Would it work?
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Edit: Since you indicated that there is inj pulse, there should be nothing wrong with CKP sensor & wiring.
I don't have Painless. I have the stock wiring.
Not sure if the colors are the same on yours...Yellow-CKP Sens/Sig In.....LT GRN-Ignition....Yel/Blk-Ref Lo
Yel/Blk was open on mine. While I referred to "ground lead", this lead has a control voltage from one end, and a ground at the other end.
Since you've already replaced the sensor, obviously it's not that.
I checked for continuity on each lead by disconnecting the battery, then pierced/stripped each wire on the CKP sensor side of the 3-wire connector. By doing it this way, you're verifying that both ends of the connector are 'good'.
I then placed a ground where each wire had been pierced. Then find the corresponding ground at the ECM end of the cable.
To make this easier, you could remove the CKP sensor & wiring.
This problem was solved last year, so I can't remember exactly which way the voltages/grnds are. -12v would prob leave the ECM @ on the LT GRN. My schematic doesn't indicate which way everything goes.
I don't have Painless. I have the stock wiring.
Not sure if the colors are the same on yours...Yellow-CKP Sens/Sig In.....LT GRN-Ignition....Yel/Blk-Ref Lo
Yel/Blk was open on mine. While I referred to "ground lead", this lead has a control voltage from one end, and a ground at the other end.
Since you've already replaced the sensor, obviously it's not that.
I checked for continuity on each lead by disconnecting the battery, then pierced/stripped each wire on the CKP sensor side of the 3-wire connector. By doing it this way, you're verifying that both ends of the connector are 'good'.
I then placed a ground where each wire had been pierced. Then find the corresponding ground at the ECM end of the cable.
To make this easier, you could remove the CKP sensor & wiring.
This problem was solved last year, so I can't remember exactly which way the voltages/grnds are. -12v would prob leave the ECM @ on the LT GRN. My schematic doesn't indicate which way everything goes.
Last edited by gMAG; Sep 29, 2011 at 10:55 PM.
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I will have to listen again. What could it mean if in fact the injectors are pulsing. I listened to it 2 weeks ago and I thought I remember hearing them. Then again, I'll have to check tomorrow.
If you get a noid light you can disconnect on of the injector plugs and watch the pulse. Agreed, that if the injectors are pulsing but you have no spark, then it is not related to the crank circuit.
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About the coil driver(s)...wouldn't that be located in the ECM?
I'll be checking out my own ECM circuit description to verif this.
I can't picture any of the electronics being outside of the ECM.
I'll be checking out my own ECM circuit description to verif this.
I can't picture any of the electronics being outside of the ECM.
The 'rental' for the lamp is free at AutoZone/Advance Auto. You get your deposit back upon return of the lamp set.
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You have probably lost the 5 volt reference to the cam sensor. If i am not mistaken that is what a 41 code is. That would explain the low voltage to the MAP sensor code which is also 5 volt reference. I would seperate the MAP and CMP circuits from the computer and see if you have a short to ground on those circuits. You may need to wiggle the wiring harness while watching your ohm meter to find the rub through or fault. Then see if those pins have a 5 volt output at the ECM when the key is on and only those circuits are out of the ECM connector. If the 5 volt supply is gone, so is the ECM, but triple check all 12 volt power and grounds to the ECM first.
The injector pulse when you cycle the key is a fuel shot in anticipation of the crank signal as you are turning the key, like an accelerator pump shot.
Some codes are set in non-volitile memory so that they are there until the code passes a number of times or a scan tool asks for them to be erased.
The injector pulse when you cycle the key is a fuel shot in anticipation of the crank signal as you are turning the key, like an accelerator pump shot.
Some codes are set in non-volitile memory so that they are there until the code passes a number of times or a scan tool asks for them to be erased.
Last edited by Brian68; Sep 30, 2011 at 12:46 PM.
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so this pre start up injector pulsing... is this a stand alone command by the ECM to the injectors and it is not related to the crank sensor? Will I get injector pulse if the car wont run while cranking? Thanks for any additional info.
The crank sig is sent to ECM which then puts out the inj & coil sigs.
It is possible that you can have no spark, but have inj pulses. This is highly unlikely, though.
That's why it would be good (& easy) to check for inj pulse.
Brian has a good point. That code 41 is assoc with the trouble he describes and is another good place to look.
Pick any inj. Then pull that inj's 2 wire plug off. Plug the noid into the harness to receive the inj pulse. Then crank, and look for the noid lamp to flash.
Staging Lane
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I apologize for my newness to the systems.
