LS1 24x - Lost sync Reason 91 - bad rpm signal, won't start.
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LS1 24x - Lost sync Reason 91 - bad rpm signal, won't start.
Hi,
My first time installing Ms3/MS3x on a LS1 24x (only familiar with 60-2 wheels from past experience)
U7 is not an LM2904. I made sure to replace it with a MC33072
Engine won't fire. RPM's seem to cut in and out. Pot settings for crank and cam were per the manual....
crank:
"c) With a small screwdriver, turn the pots, R52 and R56, about 12 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.)
d) Turn R56 back about 6 turns clockwise. "
cam:
For LS1 type sensor or logic modules inputs
a) Ensure JP7 is not jumpered.
b) Turn both pots (R11 and R32) 7 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.)
c) Then turn the top one (R11) 3 turns clockwise.
I am not sure how to understand the composite log. Does anyone have some insight?
Thanks!
My first time installing Ms3/MS3x on a LS1 24x (only familiar with 60-2 wheels from past experience)
U7 is not an LM2904. I made sure to replace it with a MC33072
Engine won't fire. RPM's seem to cut in and out. Pot settings for crank and cam were per the manual....
crank:
"c) With a small screwdriver, turn the pots, R52 and R56, about 12 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.)
d) Turn R56 back about 6 turns clockwise. "
cam:
For LS1 type sensor or logic modules inputs
a) Ensure JP7 is not jumpered.
b) Turn both pots (R11 and R32) 7 turns anticlockwise (sometimes you may feel a "click" when the end position is reached, they can't be damaged by turning too far.)
c) Then turn the top one (R11) 3 turns clockwise.
I am not sure how to understand the composite log. Does anyone have some insight?
Thanks!
Last edited by pac1085 on Mon Aug 25, 2014 7:55 am, edited 1 time in total.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Bad RPM signal - won't start
Well, the top signal is the cam, that looks fine. The middle is the crank, you are getting a signal, and bottom in red is the sync loss. There is lots of that, it shows as error reason 91. You'll have to dig through the documentation to find out what that means.
Graduate of EFI University.
I build, repair, install and tune Megasquirt systems in North Dakota and beyond!
I build, repair, install and tune Megasquirt systems in North Dakota and beyond!
Re: LS1 24x - Bad RPM signal - won't start
take a pic of your board, some times the pots don't match the build instructions and get installed backwards
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Re: LS1 24x - Bad RPM signal - won't start
Thanks, but this isn't a new board - the pots worked fine on the last engine (not an LS, but used both crank and cam sensors) before I switched it over.
Anyone happen to know what sync loss reason 91 is? It is not documented anywhere that I can see.
Anyone happen to know what sync loss reason 91 is? It is not documented anywhere that I can see.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Ok, I found a post referencing what reason 91 is. something with the cam.
I put it in semi-sequential and wasted COP and i get a stable RPM signal now.
I put it in semi-sequential and wasted COP and i get a stable RPM signal now.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Still having issues starting the car, even in wasted spark/semi seq mode. I don't see any lost sync though, and the RPM looks ok..
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
can anyone tell if there may be a mechanical issue with the engine timing based on the composite log? I installed the cam dot to dot with the crank and it appeared fine, but I can't rule it out. It is a new engine I built, never fired before.
BTW, I confirmed that all of the fuel and spark outputs are wired correctly in output test mode. Had a nice big backfire when I tested the ignition coils in the car.. (so the fuel is there )
Thanks!
BTW, I confirmed that all of the fuel and spark outputs are wired correctly in output test mode. Had a nice big backfire when I tested the ignition coils in the car.. (so the fuel is there )
Thanks!
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Can't tell any physical timing issues from the composite log. Have you checked that the commanded timing and the actual timing coincide?
Graduate of EFI University.
I build, repair, install and tune Megasquirt systems in North Dakota and beyond!
I build, repair, install and tune Megasquirt systems in North Dakota and beyond!
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
I haven't yet (trying to avoid cranking it as much as possible, since the engine is new) However, I'm starting to think it may be related to the crankshaft input? If I look at the composite logs, and compare them to this, I notice the crankshaft signal isn't even close to matching:
Would this be related to the R52 and R56 settings? I have them set exactly as listed in the manual.
Thanks for the help so far. I don't mind shooting over some cash via paypal to anyone that can help fix it
Would this be related to the R52 and R56 settings? I have them set exactly as listed in the manual.
Thanks for the help so far. I don't mind shooting over some cash via paypal to anyone that can help fix it
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
This is nothing to do with the pots settings.
It looks like the cam is maybe 90 degrees out?
If you reconfigure for wasted-COP and semi-sequential fuel, the engine ought to run without the cam input.
James
It looks like the cam is maybe 90 degrees out?
If you reconfigure for wasted-COP and semi-sequential fuel, the engine ought to run without the cam input.
James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Thanks James. I'm positive the cam was installed correctly - "dot to dot". I checked it many times before putting the front cover on. I don't see how it could be 90 off (unless a manufacturing defect by Comp Cams). I also checked with the company that designed the cam (Speed Inc) and they said that is the correct way to install it.
Is it OK that my crankshaft signal doesn't seem to match up to the one in the LS1 manual? It seems to have a completely different pattern in the composite log, vs the printout from the manual. I looked at other posts of people having scoped the LS1 crank and it seems to match the diagram in the manual.
Is it OK that my crankshaft signal doesn't seem to match up to the one in the LS1 manual? It seems to have a completely different pattern in the composite log, vs the printout from the manual. I looked at other posts of people having scoped the LS1 crank and it seems to match the diagram in the manual.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
The polarity of the crank signal seems to be inverted.
Jean
Jean
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Find attached a composite log from my own LM7.
The cam transition needs to occur around the middle of 5 pulses of one polarity, then 5 pulses of the other polarity. In my log this is showing as 5 "long-short" then 5 "short-long". If it isn't happening like that (yours is not) then something is out of phase between crank and cam.
James
The cam transition needs to occur around the middle of 5 pulses of one polarity, then 5 pulses of the other polarity. In my log this is showing as 5 "long-short" then 5 "short-long". If it isn't happening like that (yours is not) then something is out of phase between crank and cam.
James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk
My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Graphical view from that composite log.
JamesI can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk
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MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Thanks James, I now understand why you are suggesting the cam may be 90 off. It also explains why the car still won't start in semi-seq/wasted COP mode. I will pull the front cover and check tonight. This seems really odd. If I have to, I will put the stock Lm7 cam back in.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Ok, you can take my MAN CARD away. I installed the cam 90 off. Thank you again James, for pointing me in the right directions by looking at the datalogs.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
Ooops!!!pac1085 wrote:Ok, you can take my MAN CARD away. I installed the cam 90 off. Thank you again James, for pointing me in the right directions by looking at the datalogs.
No bent valves I hope?
James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk
My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
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Re: LS1 24x - Lost sync Reason 91 - bad rpm signal, won't st
No bent valves It seemed to be exactly 90 off - the exhaust valve would open when the intake should have, and vise versa... quite interesting to see.. lol.
Current:
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X
1995 Firebird Formula 5.3 LM7 Engine / 4L80E with MS3/MS3X 1.3.2 and Microsquirt Transmission Controller
Past:
1997 Audi A4 2.0TQM
MS3/MS3X