CAS problems not showing RPM while cranking but show if turned by hand
 

Alright this is getting frustrating here, this is what going on:

With the CAS in the engine and trying to crank now that I've swapped my dual shielded wiring in for it I get basically no RPM showing. Or if I do I now get about 30rpm ish. And nothing obviously fires up.

With the CAS out and me spinning it by hand, I can spin up to about 2000 rpm (shows on Megatune), I get pulse width to the coils. I can hear the injectors ticking, so basically showing functioning operation. So the wiring is all good, and the Megasquirt can see everything fine.

So what's happening when I try to crank it? Before I swapped the new shielded wiring I was seeing about 300rpm spikes, but from seeing things now with the shielded wiring, those spikes I think were just noise in the wire from something. And without the noise its showing next to nothing (atleast the shielding is working). Anyways if you guys have any ideas let me know.

Are you running second trigger ?

If so, it sounds like you probably have noise on the second trigger signal, which is common on rx7's. You can get rid of it by putting a .01 uF cap across the G+ and G- wires where they attach to your second trigger conditioner.

Ken

Yes I'm running second trigger signal. I thought I had it in there ... but maybe I overlooked it. I'll double check tonight again or tomorrow sometime. If i don't have it in there and it works ... I'll give you a million forum cookies :D:D:D.

I don't recall seeing a 0.01uF capacitor on your board at G+/-.

Also, remember that the shield should be grounded at the ECU end only.

The shield is only grounded at the ecu end. You should see the wiring now Aaron .. its worth a trip down just for that ;) lol

Alright I tried placing a .01 cap (didn't solder on on the board but I tossed it inbetween the 2 connections on the DB37 cable at the megaquirt. The result is now I don't even see one single RPM on Megatune ... so I take it then that the occasional 20/30rpm that I saw before were just noise from something then. When I spun it by hand it was still functioning fine. Any other clues?

Just wanted to add that the megasquirt is grounded thourgh the negative battery terminal and the positive right off there too (THis is temperarily till I get the relays in there for it).

I just wanted to add more to the frustration, if I take the cas out, crank the car, spin the cas by hand it still shows normal operation also, so its not like its noise from the starter or anything disturbing it. So the only thing changed literally is the CAS being out of it spot in the engine ...

Yeah, it's something I've been adding more recently. I have not even added it permenantly to the board design yet.

Ken

Strange, try grounding the MS to the engine.

Ken

Ya really strange ... I'l try doing that and i'll report back

Have you tried adjusting the cas pickups closer to the wheels?

Why would I need to move the pick ups closer if it picks up a signal already? For no reason I tried taking resistance while it was in and out of the engine to see if there are any variances but its all identical. So its no like its shorting or something.

I haven't tried grounding the MS to the engine as it started snowing here but when I'm free next I'll do so. Do you want me to ground the whole thing to it? Or could I just add another ground to the engine.

Now I might be wrong but what if the Megatune only picks up a signal after spinning the CAS up to a certain speed. Would that make sense? Would that be possible? Its only me trying to do everything but I'm not sure what rpm the injectors start to fire up.

Did someone else write this? It's worked for others.But you are farther along then I am with mine so I would listen to what muythaibxr suggests. Grounding correctly is important(like to the engine) as muythaibxr constantly stresses,so that sounds like a good place to start.

When I'm saying I'm not getting any rpm in that post is when the CAS is being spun by the engine. When it's lifted from the engine and I turn the gear by hand it shows RPM hence me saying "When it was spun by hand it was still functioning fine". Thats where the porblem lies, why would it work with it out side the engine but not inside.

I'm guessing because you are spinning it faster by hand and getting a stronger VR signal then when cranking.

I'm saying ground it to the engine b/c the body of the CAS is touching the engine.

The factory also grounds the stock ECU to the engine, not the battery, I believe so that anything that uses the engine as a ground has the same ground reference as the ECU.

IF you ground the MS to the battery, in some cases if some of the wiring isn't that great, you can create a ground loop.

Ken

Alright thanks for the info. Now I have to repull my ground from the inside of the car to where it was in the engine bay. Still snowing here so still have to wait to try it out.

alright I tried going back at this today with no luck again. I tried hooking the ground to the engine with some results. atleast now I'm getting rpm showing while cranking with a peak of about 350rpms, but most float around 150ish -200. I went in the start up/idle setting changed the cranking rpm to 150rpm instead of the 300 rpm but still no luck. Also I'm still not sure if those are actual rpms or just spikes neither. The reason that I'm saying that because I'll see the needle move up there but still no injectors firing and not showing rpm tach on megatune move like it would on the cars dash.

Now just to make sure as I haven't played around with the software much, when I wrote that 150rpm for start up, I clicked burn to ECU, then I closed it. Thats all I would need to do correct?

Also playing around with it some more, when i was turning the CAS by hand and cranking it, it finally chugged as in it seemed like it sparked in atleast one chamber trying to turn it over. So there's hope but seems like I'm still far from it. I really don't know what else to try.

I am having a similar problem with one the car I am working on. I am going to check all ground on the car. I will let you know how I make out, going to try tomorrow.

I have tried grounding at the engine, at the battery, on the chassis, so really unsure. What is yours doing exactly?

the exact same has yours. I removed everything and tried it on the bench and it worked perfect. So I have no idea what it could be. But I going to take everything out and start over. I used the same setup in my other car for 2 years with no problem. Remove and place it this car and can't get it to work. So it must be a grounding or power issue with this car.

The other one that I might try doing is shielding the power cable as Muythaibxr has suggested previously.

I had the exact same problem! I had actually soldered my VR pots in back to front and was limiting the signal with them turned anti clockwise. Everytime I turned it by hand it would register but the engine couldn't crank fast enough to get a signal through. I just mucked around with the pots until I had a brain wave to turn them back all the way the opposite direction. Then I got spark.

is that both pots on the Megasquirt or just the one?

I had both pots around the wrong way. However I don't know if it is whats causing my idle problems. I have heaps of noise at idle and the tach is jumping from 800 to 8000 rpm. I just assumed the pots are a variable resistor and it doesn't matter which way they are positioned, it just changes the direction required to increase or decrease it. Am I correct in assuming this?