No RPM problem is with c12

[panders_123]

I am putting together a MSII. I have the unit completed but have no tach signal. I was following the voltage through the tach chanel and got to C12. When checking c12 with a volt meter I get an open line. By accident I had the Stim attached and running while checking the resistence across c12. The stim started to responsd with a fuel pump light and the injector signal. I ordered replacement capacitors from Digi-key and DIY. I put in a new C12 and get the same results. As soon as I jump C12 I get all the required responses on the Stim. Questions:

What is the correct way to check a capacitor with the fluke mulitmeter?
Do you think I have a bad batch of Capacitors or is something else happening here?

Paul

[Bernard Fife]

Paul,

What board version and code are you running? If this is a V3 board, I assume you are using the Hall input. Do you have the XG1-XG2 jumper in place? The instructions tell you to leave C12 empty in the standard build, so you might want to carefully recheck your build against the instructions in 50.a.: http://www.megamanual.com/ms2/V3assemble.htm#input

You might also want to check the tips here: http://www.megamanual.com/ms2/V3trouble.htm

http://www.megamanual.com/ms2/v3pcb_3.gif

Lance.

[panders_123]

Thanks Lance, I am building the V2 version 2.2 and I am using going to use a negative signal from my coil. The instructions tell you to use C12 and jumpers from XG1 to XG2, and both the D5 and D8 need to be jumped for the Stim to work. All of those are in place.

Once interesting thing. I made the resistor and LED tester as shown in the trouble shooting guide. While the C12 capacitor is out if I stick that in it's place I get a signal to the JimStim.

I get more confused everytime I touch this thing. I have been through the trouble shooting guide with very little success

Thanks for you input.

[Bernard Fife]

Paul,

In that case, the schematics are here: http://www.bgsoflex.com/v22/megasquirt_ShemV2.2.pdf The troubleshooting guide is here: http://www.megamanual.com/v22manual/mass.htm#trouble

Is the optoisolator (U4; 4N25) in a socket? Is the IC the right way around (notch matches PCB, or dot for pin #1 which is the square pad on PCB at the notched end of the silk screen)? Is the soldering good and without any bridges, cold solder joints, or excess residual flux? Have you washed the board in 99% isopropyl alcohol (rubbing alcohol)?

What is the resistance from the DB37's tach pin (#24) to each leg of C12? What is the resistance from each leg of C12 to ground?

Lance.

[panders_123]

lance, I have checked for bridges and any cold solder joints. None.
I cleanded any excess flux off the board and it looks clean.

From pin #24 to C12 the resistance to the top(furthest point from (www.grippo....) is 382 ohm, to the bottom(closest to (www.grippo....) 7.72K ohms.

ground pin to c12 is as follows. the bottom(see above) is .2 ohms to the top(see above) is 16.60 and dropping.

I was doing more testing today and anytime I send the circuit to ground while testing the Jim Stim comes on.

Example, the the hole near r29 to ground on D1 Jim Stim lights up with the FP light, and the Inj1 and inj2 lights function. The injector light on the ms2 comes on.
The same happens when i go from ground to, D5, R10,D8, C12 only on the top side, but not the bottom, Pin 1 on U4

[Bernard Fife]

P_123,

Could you post a few close-up pictures of your board, especially the area around U4 (both sides)?

Lance.

[panders_123]

Will do, I have to find a camera that meets the requirements of this website. What I have shoots to large a shot.

[panders_123]

120126-102747.jpg

120126-102747.jpg

120126-102820.jpg

[Bernard Fife]

P_123,

That looks okay from what I can tell. Where do you see: http://www.grippo....? Is this along the bottom edge of the board (furthest from U5)? I can't see this in your pics, but that might be because it is out of focus. If you could post a pic of the whole board, it might have a bit more resolution (due to close focusing issues).

What code version?

The circuit is known to work, and thousands of people have used this circuit successfully. It's not impossible that the stim is the problem, I suppose (no common ground, reversed polarity on the stim, or something silly like that). However, I know nothing about the JimStim, so you will have to ask its developer for support on that.

If this were mine, I would compare everything in the tach circuit schematic to your board; everything joined by a line should have much less than 1 Ohms resistance (the multimeter leads probably have 0.2 to 0.4 Ohms resistance, so you have to subtract that from your readings).

v22.GIF

I would also recheck the assembly instructions for the tach input circuit against your board very, very carefully: http://www.megamanual.com/v22manual/mass.htm steps 45 - 51

Lance.

[panders_123]

The code version says "MSv30BG" i think, this is on the cpu

I have attached new pictures for you to review.

I have tried the unit in the car but lose my injector firing a couple seconds after cranking starts. Is the fuel pump signal required for the Ms to keep the injectors firing or do they shut down if it does not sense the fuel pump is running?

[Bernard Fife]

P_123,

The processor has no way of knowing if the fuel pump is actually running (it only knows if it has told it to run). So it doesn't cut the injectors.

What does cut the injectors is a lack of a tach signal. Can you do a datalog of a starting attempt, and post it here with your setting file (.MSQ).

Also, you will have to be carefully that the black tubing on the MAP hose doesn't touch any pins on the bottom of the board. That tubing is likely a bit conductive, and this has caused problems for others in the past. Wrapping it in a bit of heat shrink tubing (but not heat shrinking it) often helps.

Lance.

[panders_123]

I now have everything hooked up correctly so I am seeing good data. The tach signal is either spiking or dropping out while the car is turning over. I currently have both diodes in the tach signal circuit jumpered. Should I take the jumpers off and see what happens? I also am seeing inrichment coming on, is this to early, should I change something in the tuning set up?

Thank you,

Paul

[Matt Cramer]

If it's wired to the coil, take the jumpers out.