Megasquirt - X1/9 - no go

SVreX wrote: Fired right up once we used TDC instead of BDC.

Ya think?

Yeah, I even had a shop manual with a diagram. It just made so little sense for the marks to be on the bottom that we were SURE the diagram was just a little off.

Once we got under the car, we found the diagram was actually quite accurate. duh!

I changed the trigger offset angle/offset to 0 and it tries to start. It coughs and sputters but just won't keep running.

I did notice the RPM signal will occasionally jump to 10,000 or so even when the key is just in the on position. The triggers the pump and MS dumps fuel in the cylinders.

doh

Dude, you got twitchy wiring somewhere. Try this: turn the ignition on with a laptop connected to the MS and start wiggling the engine harness. Look for whatever causes that RPM signal to jump, then start checking that harness real careful.

How much can you turn the distro? You also might need to be in 'next cylinder' mode from the sounds of it. Your trigger offset NEEDS to be larger then your max advance plus about 10deg.

Distributor is locked in the same position it was when the car ran. It doesn't turn at all right now.

Hopefully I can get it home tonight and play with it more.

Thanks.

I hear ya, but the stock ecu might be interpreting things differently and already might be acting in the 'next cyl' mode. You might also be able to swap VR+/- to move around the trigger point, or change the MS from VRout to VRoutinv.

I swapped VR +/- and could not get an RPM signal at all.

What is the correct way to determine trigger offset?

http://www.msextra.com/manuals/MS_Extra_Software_Manual.htm#Sparkset

Better then anything I could re-write here. Generally the easiest way is to ask someone else that's done it on your type car already. On cars where I don't know it, I set it to 60 and rotate the distro until it runs then sync the timing in with a timing light and turning the distro more or changing the offset angle.

The trouble with copying someone else's settings on a Fiat is that the distributor can spin 360 degrees on it so the offset can literally be anywhere. If the timing light is spot on, your offset is correct.

The timing light was dead on before, so I just need to take the VR Sensor paddles out, turn them to where they point at #4 (timing is done on #4 on the Fiat) and put everything back together?

Or just rotate your distro until it runs then worry about the rest.

I got the car started yesterday.

But now the injectors are not firing.

I broke out the multimeter and I am getting 2.3v and 3v between injector bank 1 and injector bank 2 and ground when MS is powered on.

I disconnected everything from MS, only leaving power and ground connected and I still get voltage on the injector pins, which seems to float up to about 9v.

Any ideas what could cause this?

With MS disconnected, the injectors should have about 12v on both pins, if you have it wried up normally. Typically, one side of the injector goes to +12v, the other gets grounded through the MS. Is that how you have it wired?

Yes. The injectors have switched 12v on one side and the line going back to MS on the other side.

Pins 32+33/34+35 have voltage coming out of them, which worried me. I know MS switches that to ground to fire the injectors, but when MS isn't grounding that, is there supposed to be voltage there?

m4ff3w wrote: I got the car started yesterday. But now the injectors are not firing.

So what'dya do to get the car started? The wiring sounds correct not sure what the voltage should be for those particular injectors. Although 9v should fire most injectors...at the junkyards I've tested them with the 9v Duracell battries and they click on/off just fine.

I get 12v to the injectors on the +side of the harness. But MS itself is putting out voltage where it is supposed to switch ground to fire the injectors.

This is even if I remove all wiring from MS with the exception of power and ground.

Hmm, are you sure that output from MS is not meant for a relay that will do the switching for it? Even if it isn't you could put a relay infront of it and have it switch the ground line on/off as a test?

The fuel pump circuit does the same thing. about 3v on the line that ground the relay for it.

It does correctly ground, but when it isn't switched to ground there is 3v.

You said you got the car started,how and for how long? and you say the injectors are not firing even though MS grounds them correctly?

I got the car started Saturday, for about 20 minutes total. Had a massive vac leak from an injector o-ring that didn't get replaced. I repaired it and tried starting the car the next day. It wouldn't start. I checked for voltage to the injectors and that was when I discovered I had the proper +12v on one side but was also getting voltage on the other side as well.

I am now not certain if MS is grounding them correctly (it is the fuel pump) as I removed all the wiring thinking I had something wired incorrectly. I also needed to mount things in a more permanent way.

I'll get everything hooked back up tonight and see if MS is grounding them correctly or not. I can't get an RPM signal from my stim, because I am using a VR sensor, so I can't test it here at work.

Not sure if 3v differential is normal or not, do the injectors spray constantly when plugged in, or nothing?

Does this car have low impedance (3ohm or so) injectors? If so did you have the PWM limits set?

three volts sounds like a processor voltage level. Are you driving the injectors from the processor or does the signal go through relays so as to provide enough current?

I do not know about the megasquirt system, but if you tried to drive too big of a load with the processor outputs, you could damage the processor. However, since you are still switching 0-3volts, I do not think so. Try a relay.

The injectors are driven by a injector driver (big, heavy duty transistor). It is possible that the small voltage you are seeing on the pinouts of the MS are the bias. I don't have the schematics in front of me right now. There are no relays controlling the injectors. I don't know of any EFI system that uses relays to fire the injectors, but I don't claim to know them all. With the early Bosch, there's no telling what all they did with relays, but that would be a harsh environment for a relay.

So, do the injectors fire when you crank? What does MegaTune look like when you're cranking?