MS1 LS1 no start while cranking

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jartech007
MS/Extra Newbie
Posts: 1
Joined: Thu Feb 02, 2017 9:47 pm

MS1 LS1 no start while cranking

Post by jartech007 »

Hello,
The last 60 days I have ben trying to get this engine to fire. The engine I pulled myself from a Silverado 1500 2001. The MS1 has been modified to run the engine following the instructions for 24X trigger wheel. I have spark and fuel. All grounding is now to a single point in the block. It does the attempt to start (hence the 300+ rpm while cranking) but it does not start. as you can see I just installed a new crank sensor and it didn't change anything. The crank signal wire had the grounding on  the shield removed and didn't change the issue. I did refill the tank with fresh fuel and the fuel pump is a brand new one.  I am using 5V for the crank and cam signals that I am sharing with the TPS V ref. I had check my wiring about 8 times already since December, but I can do it again if you see the issue is there. wiring has been performed following the link below. Power for the MS1 is directly from the battery.  MS1 has the latest firmware and has been refreshed a couple times already since then. I have added squirts of starter fluid to the engine that has not made any difference as well. I installed a new battery 2 weeks ago.

It sounds to me that the timing is off on the engine, but I don't know how that could be possible since the engine is OEM and the sensors should be in sink to get spark and rpm. I have not change the cam sensor yet but I do have it brand new.

I have check the MS1 ecu a couple times to see if there is any issues there, all wiring is good. I did the test for the injector driver and pass all testing procedures. I saw spark on the cylinder 1,3,5,7 so I know each coil is getting triggered.  

I think this is everything I got. Let me know if you can think of something that can help me.
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: MS1 LS1 no start while cranking

Post by Matt Cramer »

MS1 with a 24X wheel is really not a good idea - any timing chain stretch, and the timing will shift by 15 degrees back and forth. Is an upgrade to MS2 in the budget?

The tooth log looks as if it may be reading the wrong edge of the sensor as well.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
Monzsta
Helpful MS/Extra'er
Posts: 46
Joined: Sun Oct 26, 2008 5:05 am

Re: MS1 LS1 no start while cranking

Post by Monzsta »

There was a bug in the code for the LS1 wheel. It was addressed in MS2 and 3. I don't know if it was fixed in MS1.

Also the LS1 triger wheel is fixed to the crank. Timing chain slop has no effect on it.

http://www.msextra.com/forums/viewtopic ... 25&t=44056
'98 Trans Am LS1 A4
Ms2 3.0 board, controlling fuel and spark.
Matt Cramer
Super MS/Extra'er
Posts: 17499
Joined: Thu Apr 16, 2009 8:08 pm

Re: MS1 LS1 no start while cranking

Post by Matt Cramer »

Monzsta wrote:There was a bug in the code for the LS1 wheel. It was addressed in MS2 and 3. I don't know if it was fixed in MS1.
The MS1 never had a dedicated LS1 wheel decoder, and while the MS2 and MS3 code are developed off a similar code base, MS1 code is not.
Also the LS1 triger wheel is fixed to the crank. Timing chain slop has no effect on it.

http://www.msextra.com/forums/viewtopic ... 25&t=44056
The MS2 and MS3 code looks at the length of the teeth to identify which tooth is which when using the LS1 decoder. MS1 is not able to measure tooth length, so it must rely on the cam sensor to distinguish which tooth is which. It cannot operate purely from the crank trigger like the other decoder and so it is vulnerable to timing chain stretch effects in a way that MS2 and MS3 are not.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
DaveW
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Re: MS1 LS1 no start while cranking

Post by DaveW »

There's no reason why it won't run an LS1 quite happily, I've been running mine for 10 years now on MS1-Extra so if your budget won't stretch to MS2/MS3 then don't despair. It runs better and smoother on MS2 but it's not so much better that it's a necessity. For some reason every time I've built an MS2 for mine someone's asked me if they could buy an MS2 for another project and I've agreed, reverting my engine back to the "old faithful" MS1-Extra !

One of the biggest issues I had with mine, once the LS1 mode had been added for the cam signal, was that noise/spikes coming into the cam and crank sensor inputs was screwing with everything giving me inconsistent timing and making the engine impossible to start. You need to look very carefully at how you are interfacing between the MS1 and the Cam and Crank sensor signals. On mine, as you are doing, I run the sensors at 5v and the signal coming from them, in theory, is a nice clean 5v square wave so they can be run straight into the CPU and originally I just had a 330 ohm resistor in series to mitigate any potential damage to the CPU.

Adding a small capacitor between each input and earth filtered out the noise and immediately fixed the issues I was having, giving rock solid timing as you would expect. The value of the capacitor isn't all that important but the larger the value the more you will delay the timing, too small and it won't be as effective. I'll have to dig out the original documentation I did but off the top of my head ISTR that around 22pF was a good value.

Edit... Just checked and it was actually a 0.1uF capacitor that I put across each input on mine.
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