MS1 - hard/NO starts

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Wed Jun 18, 2014 11:34 am

sorry for the long delay in response...

Turning false trigger protection off does seem to change the way the missfires happen (they seem to happen for a shorter duration) but the problem is still there at the same high rpm band.

Also, I swapped processors and then an entire MS (wired the same) and the problem is the same.

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Thu Jun 19, 2014 10:50 am

Also, played around with the pots on the VR conditioner circuit. R56 is set about 1 cw turn past getting no crank signal.

Interestingly, R52 responds best full ccw. The further I turn it cw the lower my "wall" rpm seems to be? Any ideas why this might be??

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Re: MS1 - hard/NO starts

Post by Matt Cramer » Tue Jun 24, 2014 10:35 am

This may be difficult to figure out past this point without throwing an oscilloscope on the signal.

Not sure if I mentioned this before, but I've seen a few cars that started better on an upside-down disc. You need to make some major changes to the wheel decoder settings to get the right trigger angle and teeth though.
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Re: MS1 - hard/NO starts

Post by Spoolin6er » Tue Jun 24, 2014 11:05 am

What specifically would you want scoped? As far as I could see everything looked perfect while scoping on the bench.

My starting issues have been almost completely solved my replacing the battery. Started other cars fine, but couldn't keep a clean rpm signal with it while cranking for some reason. Once I solved the cranking issue I started looking into my high rpm tach spikes.

So far I have done the following:
- Switched to the vr input circuit
- added caps to clean up the board voltage
- replaced the battery
- grounded the ecu to one point on the head
- ran my own shielded CAS wires (grounded at ms)
- replaced distributor and coil (using DIYAutoTune trigger disc in both orientations)
- eliminated injector pwm by adding injector resistors
- swapped ms boards and processors

No idea where to go next

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Re: MS1 - hard/NO starts

Post by Matt Cramer » Mon Jun 30, 2014 8:59 am

Spoolin6er wrote:What specifically would you want scoped?
The sensor output and the output of the VR conditioner.
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Re: MS1 - hard/NO starts

Post by Spoolin6er » Mon Jun 30, 2014 2:31 pm

[quote="Spoolin6er".]
I don't have a Jim Stim so I pulled the MS and my distributor out and wired my optical CAS to my early gen stim. I hooked the distributor shaft up to a dremel and went to testing. RPW looked perfect every where except right around 6000, tach signal was intermediately dropping out to around 2000. Looking at the log showed that "spark angle was dropping sometimes when rpm wasn't? Maybe it has a slightly different sample time?

https://www.dropbox.com/s/sr8avgc5xqnf0 ... _bench.png

I hooked up the scope again and found that the lower voltages I reported earlier were due to me setting it up wrong. This time I got a perfect square wave at the "tachselect" pin with a magnitude around 10-11v (which is what my power supply was putting out). And another perfect square wave at the VROUT pin with a magnitude of about 1.3v (i'm using the VR conditioner). I couldn't see any change in the wave form at either location even when the tach was dropping out in MT.[/quote]

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Thu Apr 16, 2015 9:05 pm

Well I'm back at it again...

I've decided to switch to Maxima COP's and completely re-wire my engine harness in a final attempt to eliminate my high rpm CAS signal break down. Now I have some choices...

I'm debating what is the best way to power everything, particularly the MS, CAS, and coils. I can't wrap my head around using different power "sources" since they all eventually make it back to the battery. Does it even matter?

Previously I was powering the MS and CAS from the ECCS relay (B/W wire), and everything else (inj, WB, coil etc) from the ignition key (B/R wire). I was using the key ign signal to close a relay to ground which closed the ECCS relay. Attached is an illustration of what I had ("MS Power ver1.png") When I first set this up, I didn't realize that the current draw of the main B/R power wire all goes through the ign key!

Revisiting this, that method seems silly to me. My thought was to eliminate the ECCS relay and power the MS, injectors, and CAS from the key (B/R wire) and the coils separately with a relay. See "MS Power ver2.png"

Then I could use the OEM O2 circuit for the the WB o2 - Although this seems to draw through the key as well. OR possibly add a third relay, OR add it to the coil power relay that I just added?

Suggestions? Does any of this really matter or am I wasting time worrying about it?

Thanks,

-Matt
Attachments
MS Power ver1.png
OLD MS power setup
MS Power ver2.png
NEW MS power setup

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Mon Apr 20, 2015 2:33 pm

no thoughts on this?

Just looking for some 12v source best practices... doesn't have to be specific

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Re: MS1 - hard/NO starts

Post by Matt Cramer » Tue Apr 21, 2015 7:03 am

Some general rules of 12 volt wiring:

1. You want the injectors to be on with the key on or from the fuel pump relay - Nissan has them on full time, which can be a problem with MegaSquirt because it wasn't designed for this.

2. The wires' inductance can mean the wires do a bit of noise filtering. And the battery itself does a fair amount of filtering. If you have the ECU powered off one wire from the battery, and the coils off a totally different wire, that would do the most to prevent noise backfeeding into the ECU. You can also put a capacitor on power feed wires to add filtering.

3. Never power distributor or crankshaft position sensors sensors from the fuel pump relay. (I know, you're not making this mistake, but I'll add this for the benefit of others reading.) I've seen this done before, and the result is when the ECU shut off the fuel pump after seeing RPM drop to zero, the RPM sensors couldn't power up and send an RPM signal.
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Re: MS1 - hard/NO starts

Post by Spoolin6er » Tue Apr 21, 2015 7:57 am

Thanks!

Although if you look at the first diagram I attached (edited OEM diagram) the injectors do not seem to be powered all the time, only when the key is in run/crank.

Are there any other components that should have isolated power besides the coils? ie injectors or WB? - I plan to go back to running low imp injectors with pwm..

ie: Can I run the setup in the second picture? What does the plug and play MS use for power?

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Wed Apr 22, 2015 10:46 am

Also, been reading through this: http://www.bgsoflex.com/megameet2008/me ... gnding.pdf

Which seems to be a great presentation, but is missing a lot of explanation. One of the things I wanted to clarify was: The pdf talks about a separate high current ground plane and a 5v/sensor ground plane. Is Pin7 the only connection to the sensor ground plane? I was planning on running a separate ground wire for each sensor to avoid splices, but I suppose this is a bad idea if the ground plans are separated. What plane does pin 1 (CAS ground) go to?

*Edit* - I have kind of answered part of my question, I found this on the Megamanual site:

"4-Layer Board: The V3 PCB consists of four layers (top, bottom, and two inner layers), compared to only two layers on the V1.01 and V2.2 boards. The inner layers used for power and ground planes, and the top and bottom are used for signal routing. Considerable time was spent in the board layout design to properly separate the high-current power and ground from the sensitive digital power/ground. There are separate ground planes, one for the high-current drivers and the other for the digital supply ground, with both returning to the output connector at a single point. With this correct implementation, the noisy high-current switching grounds do not couple into the digital ground, significantly reducing noise and the resultant problems that a common ground system can create. In fact, board testing in a running vehicle with injector PWM and ignition flyback noise sources yields a digital power/ground plane noise level of 25 milliVolts."

This seems to mean to me that all of the ground pins connect to BOTH the main current grounds and the Sensor ground pin 7? So i'm guessing the purpose of the two planes is only for isolation of the high currents and digital grounds WITHIN the MS itself - how they can be isolated and connected at the same point hurts my head, but I'm assuming they know what they're talking about...

Still wondering how you guys suggest I run my 12v+ supply for ECM, coils, injectors, WB, etc...

We confirmed:
- do not run MS and coil power from the same wire

But how about:
- running a relay for injectors, coil, and WB and powering the MS and CAS from switched 12v? In this case could I get coil noise through the injector circuit back to the MS since the MS pulls the injectors to ground? The idea here was to limit the current coming from the key to limit the "IR voltage drop" that pdf talks about. Seems like normally (according to typical MS wiring diagrams) a relay would be used, but the OEM setup powers coils, injectors, O2 sensors etc directly through the key.

OR to avoid the above issue:
- run the MS, CAS, and injectors off the key (OEM fused at 30A) and the coils and WB off a relay.

I'm curios to know what the MS PnP unit uses for a power source(s)

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Mon Apr 27, 2015 5:04 pm

so, no suggestions huh? Can you at least tell me what the PnP MS uses for power?

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Re: MS1 - hard/NO starts

Post by BigLoukaT » Tue Apr 28, 2015 7:38 am

The diypnp docs show that pin 47 for 12v power to the ecu. All other power is controlled by the same circuits that power them in a stock car. Exception being wideband, which needs to be powered by switched +12v.
Fuel injector +12v is provided direct from the battery (see the stock wiring in the fsm).
However, I have read that the fuel injector driver circuits are not exactly the same between the plug and play and the regular ms1/2 boards, so fuel injector +12v should be switched on a relay controlled by the fuel pump output (so they are only powered when megasquirt is ready to control them). Power to coils is likely similar

You should refer to the msextra manuals msextra.com/doc and follow the wiring recommendations within
1990 S13
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MS DIYPNP
npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Tue Apr 28, 2015 5:24 pm

Thanks, I didn't realize there was documentation like that for the PNP's...

BUT, you're wrong - I have an S14 KA24DE - the injectors DO NOT receive power directly from the battery, it comes through the key as I said before and that's what is shown in the schematics I posted ;) Don't act like I haven't searched for weeks on this stuff. There are a ton of variations of MS external wiring, each with slightly different power routing - the can't all be the "best" practice.

Looking at how the S13 PNP kit works (according to the documentation) power is taken from pin 47, well I don't see how that works since pin 47 pulls power from the ECCS Relay, which can be controlled by the MS, but how if its not powered??

S13 wiring:
Image

The S14 PNP kit states it gets power from pin 38 - the same circuit as the injectors, coil, fuel pump, IACV, air bags, and a ton of other stuff... interesting choice.
S14 Wiring:
Image

Here's what I have planned so far, any one see any issues? (Just check out the power/grounding)
http://njsr.org/pics/albums/userpics/11 ... wiring.png

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Re: MS1 - hard/NO starts

Post by Matt Cramer » Wed Apr 29, 2015 7:35 am

Spoolin6er wrote: This seems to mean to me that all of the ground pins connect to BOTH the main current grounds and the Sensor ground pin 7? So i'm guessing the purpose of the two planes is only for isolation of the high currents and digital grounds WITHIN the MS itself - how they can be isolated and connected at the same point hurts my head, but I'm assuming they know what they're talking about...
The two ground planes meet at the DB37 and tie to all the connections, not just pin 7. They are to isolate the grounding within the MegaSquirt. Here's an analogy that may help.

Imagine the ground planes are two hills that meet at a valley, the valley being the DB37 connector. And suppose there's a big rainstorm, so you have water flowing down both hills. The water represents current. The two hills are connected together, but water normally flows downhill, so it's not going to go down one hill and up the other unless something strange is going on - you'd either need a low spot in one of the hills, or the water to build up so much speed going down one hill it briefly climbs the other.

That's what the split grounds are doing. The current is flowing to the connector but isn't likely to go back up into the other ground plane.
But how about:
- running a relay for injectors, coil, and WB and powering the MS and CAS from switched 12v? In this case could I get coil noise through the injector circuit back to the MS since the MS pulls the injectors to ground? The idea here was to limit the current coming from the key to limit the "IR voltage drop" that pdf talks about. Seems like normally (according to typical MS wiring diagrams) a relay would be used, but the OEM setup powers coils, injectors, O2 sensors etc directly through the key.
That approach can work fine. Some notes on the OEM wiring makes me think Nissan decided on their wiring for these cars not because the approach was best, but that it was adequate and that they could save a dollar or so per car...

As for the MSPNP - there's actually a second circuit that switches on the ECCS relay in response to turning the key on, that doesn't tie into the main MSPNP power circuit.
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Re: MS1 - hard/NO starts

Post by BigLoukaT » Wed Apr 29, 2015 6:09 pm

Spoolin6er wrote:Thanks, I didn't realize there was documentation like that for the PNP's...

BUT, you're wrong - I have an S14 KA24DE - the injectors DO NOT receive power directly from the battery, it comes through the key as I said before and that's what is shown in the schematics I posted ;) Don't act like I haven't searched for weeks on this stuff. There are a ton of variations of MS external wiring, each with slightly different power routing - the can't all be the "best" practice.

Looking at how the S13 PNP kit works (according to the documentation) power is taken from pin 47, well I don't see how that works since pin 47 pulls power from the ECCS Relay, which can be controlled by the MS, but how if its not powered??

S13 wiring:
Image

The S14 PNP kit states it gets power from pin 38 - the same circuit as the injectors, coil, fuel pump, IACV, air bags, and a ton of other stuff... interesting choice.
S14 Wiring:
Image

Here's what I have planned so far, any one see any issues? (Just check out the power/grounding)
http://njsr.org/pics/albums/userpics/11 ... wiring.png
The s14 wiring diagram you posted shows the injectors are fed constant battery power.

Wasnt trying to minimize your research, but you will not go wrong if you look at the most current manuals available on the msextra site and follow that practice.
1990 S13
Boosted single slammer
MS DIYPNP
npx from 240sxforums wrote:i figure from my very limited knowledge about the 240 and under the hood about cars in general i would follow the sr20det trend.

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Wed Apr 29, 2015 9:49 pm

woah - well apparently there are even more variations than I thought, this is straight out of the 96' FSM:

http://njsr.org/pics/displayimage.php?p ... fullsize=1


Matt - thanks for that analogy, clears up a lot.

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Re: MS1 - hard/NO starts

Post by Spoolin6er » Wed Sep 09, 2015 6:43 pm

just to bring this thread to a close - I switched to an AEM (using all the same sensors and wiring harness) and the problem is 100% gone. What a waste of 2yrs of my life :(

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