LS1 carb with MSD 6LS controller

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twb119
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LS1 carb with MSD 6LS controller

Postby twb119 » Fri Nov 25, 2016 11:39 pm

Have a 8 year old LS1 carb with MSD 6LS controller. About 6 months ago tried to crank it up and would not fire, just pop every now and then, messed around with it for 2-3 hours and was stumped, it ran good before never any problems. Wednesday tried it and fired right up and ran fine no roughness, cranked and shut it off at least 20-30 times no problems. Well today will not do anything just pop now and then, checked every wire connection and couldn't find a thing wrong, one pipe on the driver side header was warm so its trying, sounds/feels like a timing problem, and was wondering if it could be the cam sensor going bad, not sending cam position to controller. Is their a way to test the cam sensor??? am I barking up the right tree???

Thanks Thomas

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90chevy396
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Re: LS1 carb with MSD 6LS controller

Postby 90chevy396 » Mon Nov 28, 2016 3:51 pm

First thing to check would be to hook up a computer to it with the factory pro data software and see if you can read live data. If so I would check the PIDs for cam and crank reference to see if your getting the signal. that would be the ideal situation. but not familiar with the msd system to know if you can do data logging or read live data but worth a try. or call their help line 1-888-258-3835
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Re: LS1 carb with MSD 6LS controller

Postby C1gator » Mon Nov 28, 2016 9:16 pm

Check your grounds thoroughly.

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Re: LS1 carb with MSD 6LS controller

Postby Olf Art » Mon Nov 28, 2016 10:29 pm

C1gator wrote:Check your grounds thoroughly.

Yup ..... #1 problem with any DC circuit is usually a faulty ground. JMO
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Cody25911
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Re: LS1 carb with MSD 6LS controller

Postby Cody25911 » Tue Nov 29, 2016 11:18 am

We had this problem on a water thunder LS1 with carb and MSD. We got every response from ground wire, bad MSD, need a new carb. We rebuilt the carb, no change, changed plugs, no change, checked every wire, nothing. Finally, someone bought the boat in this process and suggested they change crank and cam position sensor,,,,, problem fixed! I don't know what one fixed the issue, but it was fixed. If these sensors are bad, they will go 180* out and cause the issue. But same symptoms, run sometimes, not run the next


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90chevy396
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Re: LS1 carb with MSD 6LS controller

Postby 90chevy396 » Tue Nov 29, 2016 2:29 pm

Cody25911 wrote:We had this problem on a water thunder LS1 with carb and MSD. We got every response from ground wire, bad MSD, need a new carb. We rebuilt the carb, no change, changed plugs, no change, checked every wire, nothing. Finally, someone bought the boat in this process and suggested they change crank and cam position sensor,,,,, problem fixed! I don't know what one fixed the issue, but it was fixed. If these sensors are bad, they will go 180* out and cause the issue. But same symptoms, run sometimes, not run the next


this right here explains the reason you need access to the live data to see what the computer sees when the fault happens. bad ground will indicate on live data, cam and crank sync will show up eratic on data log. when messing with a computer controlled engine if you don't have access to the live data you will have a hard time finding the problem unless you work on that specific engine/ computer system regularly. I once found a boat with a 8100 had a voltage issue within the alternator causing voltage spikes under full load that a damn good airboat engine builder was scratching their heads about because you don't know **** unless the data tells you so. so either change parts until it fixes the issue or find a way to see the live data and do some real diagnostics work.

cars are the same way you either diagnose them with communication devices to see what the computer sees or you run around blind scratching your head. anything computer controlled cannot be correctly diagnosed without seeing what the computer is reading. even though the computer has the correct inputs at the connector doesn't mean that the computer is seeing the data correctly.

if you plan to stick with your current configuration either get correct device to communicate to the computer or find someone that has the ability to do so and keep them in your back pocket
or you can do the alternative and ask what the common cause of your symptom is and change them parts until you find it
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Re: LS1 carb with MSD 6LS controller

Postby Waterthunder » Wed Nov 30, 2016 2:02 pm

The software will only show a sync code but that doesn't tell you why. Could be a ground a sensor or a connection or a harness pin problem. but I have found several times where there was a problem but the computer didnt show any sync issues.. Over 15 years I have only seen 4 or 5 MSD LS problems,,,,, 3 were bad grounds and 2 were bad crank sensors. The problem the above boat that Cody stated I do not know if they ever brought us the boat so I don't know what the problem was. But if they changed sensors I would guess crank sesnor they tend to go bad after 5 or 6 years.

Im currious Cody25911 did you ever bring the boat by for us to look at? I only know of one other issue like this but I cant remeber who it was.
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90chevy396
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Re: LS1 carb with MSD 6LS controller

Postby 90chevy396 » Wed Nov 30, 2016 3:01 pm

You would be the one to ask considering you have messed with this system before. I am not familiar with this particular system or what pids the data would show but in most automotive applications their would be a cam and crank sync pid and most have a crank and cam pids separate. being a driveability guy I know how annoying these problems can be
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twb119
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Re: LS1 carb with MSD 6LS controller

Postby twb119 » Thu Dec 01, 2016 7:54 pm

I haven't had time to work on it. Friday and Saturday checked all the connections thoroughly, all the grounds have continuity, plus removed grounds and brushed the connections to be sure, all the sensors (crank and cam) have 12.81 volts, same as battery, voltage drop when cranking is good, all the plugs have good fire. Will have time Sunday to work on it, will get a crank sensor and swap that out.
Thanks everyone.

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Re: LS1 carb with MSD 6LS controller

Postby Cody25911 » Fri Dec 02, 2016 9:34 am

Waterthunder, It was my brothers boat. Issue was about 12 months ago now. We talked to you and you made the suggestion on starting with looking for bad grounds. You mentioned to bring it by if we had no luck, but not long after we had talked, someone wanted to buy it as is, as it had been up for sale during the time it had the problem. At that point we let them know the only thing we had not attempted was crank sensor and cam senior and said they should start there.

Just FYI, that was not a bash on your product or saying you had not offered help, just letting the original post know we went down the same road looking for the issue and basically overlooked the almost obvious now that we know what it was.

Unless of course you did invent the GM crank sensor, then yes, I am blaming you for the issue hahahaha just messing with ya!

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twb119
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Re: LS1 carb with MSD 6LS controller

Postby twb119 » Wed Jan 18, 2017 12:58 pm

I never did find out what was causing my problem, its cranking fine, running fine now. I never replaced the crank sensor, tried it right before i headed to the parts store and it fired right up, ran a little ruff for a couple of min and then cleared up, runs good now. I don't know if it was a bad connection some where and just by checking/plugging in and out fixed it. Whats weird about it it wasn't cranking one night and next day fired up with not one thing done to it. Its been run about 3 hours and cranked and shut off at least a hundred times with no issues.

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Re: LS1 carb with MSD 6LS controller

Postby getchasumairboats » Wed Jan 18, 2017 3:50 pm

Grounds cost nothing to clean and check and crank sensor are cheap. Hell I have a spare crank and cam sensor in my dry box. Aswell as a starter and both fuel pumps.
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