Faulty MS3X injector output?

[Onime]

Here is the problem I have 4 cylinder engine running with MS3 + MS3X. Everything worked perfectly until yesterday, engine suddenly began to stall, I felt fuel is shut off. after waiting about 20 mins I have tried to start engine again it started without problem but on throttle it it worked with misfires, finally one injector just stopped working.

When I put voltmeter cables on injector connector pins I get different voltage for non working connector (without engine running, just ignition on), one pin of injector connector is constant 12v so in fact I'm getting different resistance from ecu on injector PWM outputs.

For conectors that work I get about 7 to 9 volts and for connector that does not work I get 12v, I guess no resistance from ecu at all.

[Onime]

Checked resistance of injector outputs (key on) I'm getting about 12 megohm on outputs that work and about 0.3 megohm on output that does not work.

If that particular output is dead, is there a way I can use 4 spare injector outputs available from MS3X board?

[DaveEFI]

Have you tried the injector test function in TunerStudio? But do read up about it first.

Other thing is to find out just why a driver failed (if it has) before repairing or whatever.

[Onime]

Thanks for reply Dave. Yes I have tried injector test from TunerStudio and all injectors A,B,C are pulsing but D does nothing. Injector for output D is fine I tested it independently from MS. As a rescue option I consider using outputs from MS3 mainboard which forces me to move on semi-sequential from sequential and I'm not happy with that.

But I still want do diagnose the problem first, why did this happen to avoid it in future.

[DaveEFI]

Checked resistance of injector outputs (key on) I'm getting about 12 megohm on outputs that work and about 0.3 megohm on output that does not work.

If that particular output is dead, is there a way I can use 4 spare injector outputs available from MS3X board?

I've only just got an Ms3X so not well up on it yet - but if it's not possible to do what you want in software, it would be easy enough to alter the 8 way cable (or just make up a new one) that runs between the processor and X board, and to alter the corresponding outputs on the DB37.

If it is just the output MOSFET which has failed, that's also not too difficult to change, being quite large. If you are a skilled solderer, etc. The driver chip is probably best left to a pro to change.

[billr]

"When I put voltmeter cables on injector connector pins I get different voltage for non working connector (without engine running, just ignition on), one pin of injector connector is constant 12v so in fact I'm getting different resistance from ecu on injector PWM outputs.

For conectors that work I get about 7 to 9 volts and for connector that does not work I get 12v, I guess no resistance from ecu at all."

It is not clear to me how those measurements are being made. Are you reading voltage between the two injector pins, with the injector connected to the harness? If not, describe more completely where the meter probes are being connected and what (if any) load is on the injector driver being tested. My understanding is the injectors are powered with 12V immediately at "key-on", at least for this testing, not controlled by the fuel pump enable. That isn't usual or recommended, but not the immediate problem, just verify that it true as it will affect voltage readings expected at "KOEO".

[Onime]

billr Thanks for suggestion. Meter probes were connected on two pins of injector connector on harness side:
ignition was on and my injectors get 12v immediately on key.

I was getting same voltage as battery (12v) for no-working injector connector because that particular connector did not get any resistance from ECU while others did and therefore shown 7-9 volts. Here is more proof for that, which I'm not sure how to fix it yet. Removed MS3X from car and tested resistance of some components there and I think I found where the problem is. I don't know leg names for these components so I will just identify them with numbers 1,2,3:

Resistance between legs 1 -> 3 is about 1.31 megohm for all of them except U9 (Which logically is for "Injectour out D" and sure that is connector that does not work) on U9 I get zero resistance. So I think U9 is dead and that's cause for non-working output D.

[billr]

You need to have a load connected between those two harness sockets, either an injector plugged in or a dummy resistor (anything under 10K ohms should be fine). Otherwise, voltage measurements across those sockets, of from a socket to ground, are meaningless. Likewise, resistance measurements at those harness sockets are meaningless without a load connected, and if there is a load you will only be measuring the resistance of the load. You "get" no voltage from the MS ECU at those harness sockets. One is connected to 12V by your car wiring and the other is grounded by the ECU to pulse the injector.

I confess I didn't study that last reply from the OP thoroughly, as we have been through the this situation before. Somebody please correct me if I missed something or made a mistake.

[Onime]

billr yes you are right about measurements. But one thing is clear something is wrong with U9 (inj D driver I guess) so I'm giving up for now because there is lot other things to do with car for near event.

I have decided to use main fuel outputs from mainboard and use semi-sequential one thing is not completely clear it how to pair injectors for semi-sequential, I have read somewhere injectors need to be paired for cylinders that are 360 degree apart. i.e. for 4 cyl 1-4 2-3 is that correct?

[jsmcortina]

Have you tried contacting your supplier regarding the MS3X card? Even if it is out of warranty, it is repairable.

James

[DaveEFI]

Just to clarify, have to checked at J1, the 8 way connector on the X board, that you are getting a pulse to the appropriate driver when using test mode? A DVM should obviously show the same on all four in use. With a fine test probe, you should be able to probe the end of the ribbon cable with everything plugged in. If you haven't got a fine test probe, use a needle or pin with the lead clipped to that.

[Onime]

DaveEFI, thank you so much for giving idea about altering connector between Mainboard and X board that could be easier than driver swap. Just to make sure these transistor-like things on image I have uploaded are injector drivers yes? Things which legs are marked.

jsmcortina, unfortunately there is no supplier for MS in my country (Georgia)

[jsmcortina]

jsmcortina, unfortunately there is no supplier for MS in my country (Georgia)

You bought it from someone though? Ask them.

James

[Onime]

jsmcortina, I bought it from DIYAutoTune.com it came down here by mail. It is not worth for me to send it back for repair, though I could ask them for damaged parts and repair it myself.

But for now, thanks to DaveEFI, SOLUTION is this:



Cut fourth wire on J1 and connected it to 8th this made Inj out H to become Inj out D. Tested it today works perfectly Thanks DaveEFI again.