Lost rpm and sync

Building and using the Stimulator to test your Megasquirt

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subarvair
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Lost rpm and sync

Post by subarvair »

The Jimstim has been working fine so today I tried wiring in a hall effect VSS. I used MS3 pin 26 as a 5v source, one of the grnd pins on the JS board and MS3x pin 30 as the digital input. When the JS was turned on, there was no rpm or sync. I took out all the VSS connections and even reload firmware but still no rpm. A jumper is connected from the JS 2nd trigger pin to MS3x pin 32.
What could I have done that caused the rpm loss?
Mike
Matt Cramer
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Re: Lost rpm and sync

Post by Matt Cramer »

Can you post a composite log of the signal you're getting?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
subarvair
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Re: Lost rpm and sync

Post by subarvair »

Matt,
Comp, sync, trigger and tooth logs all come up blank. All gauges work except rpm and of course PW and ign advance.
When I started the VSS wiring, to test for a 5v source, I used the probes of my multimeter on the different voltage pins using the "-" of the power supply as ground. With the pins so close together, I may have touched more than one pin with the probe. At this point, all 12v, 5v and 3.3v pins show proper output.
My concern now is whether the problem is in the Jimstim or MS3 unit. If it is the Jimstim, then I will just lay that aside and wire the controller to the engine and begin the start proceedure.
Reloading the firmware solved my last problem but not this time. I even changed to another trigger pattern but no difference.
Appreciate your input or others.
Mike
racingmini_mtl
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Re: Lost rpm and sync

Post by racingmini_mtl »

Have you done the troubleshooting tests for the JimStim: http://jbperf.com/JimStim/JimStim_v1_5_ ... ml#testing ? That would be the first step.

Jean
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subarvair
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Re: Lost rpm and sync

Post by subarvair »

Jean,
Thanks once again for your guidence.
I went through the testing proceedure twice. The LED test was OK. The power supply and CPU do not get hot. The tach signal test failed. In testing the CPU pins, I do get 3.3v on 1 & 3 and show 0-3.3v on 13 and 14 depending on the position of the rpm pots. I assume the CPU pins are numbered 1 thru 8 starting at the notched end and going down the side closest to the on/off switch and returning up the other side ending with 16 being opposite 1. Does this all mean that I have a failed CPU?

Mike
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Re: Lost rpm and sync

Post by racingmini_mtl »

Does F1 get hot (assuming you have a V1.5)? And yes the numbering is correct so even if F1 doesn't get hot, it seems there is a failure. It could be one of the transistors that are driving the tach signals (Q1, Q2) but if you don't get a signal on either in the testing, it is likely a CPU issue. If F1 does get hot but not D4, then is almost certainly the CPU.

Jean
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subarvair
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Re: Lost rpm and sync

Post by subarvair »

Jean,
I see not signs of heat and feel no heat out of either F1 or D1. The # on the CPU is V2.0.3.
Would it seem to you at this point that the problem is in the Jimstim and not the controller? If so, I am inclinded to set the JS aside and wire the controller onto the engine.
If you feel it is a failed CPU, can this be obtained from you. Would it be best to send the old one into you first.
I purchased this equipment from DIY last Oct.
Mike
racingmini_mtl
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Re: Lost rpm and sync

Post by racingmini_mtl »

If the JS doesn't pass the troubleshooting tests and it was working before, it is usually a CPU failure. You can get a new CPU either from DIY or directly from me. Since you're in the US, it's likely more practical and faster to get one from DIY (I'm in Canada). And sending your current CPU is likely more expensive than buying a new one.

Jean
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subarvair
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Re: Lost rpm and sync

Post by subarvair »

Jean,
Received the new CPU today and everything is working again.
Mike
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Re: Lost rpm and sync

Post by racingmini_mtl »

Mike,

Good to know that it fixed your issue.

Jean
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