Injectors not Grounding Through MS-II

[Loki73]

Hello

I'm woking on a 1976 Datsun 280Z with a modified L28 engine. I'm using MS-II V3.57 (from DIYAutoTune.com), EDIS-6 ignition, as well as a relay board from DIYAutoTune.com. My ignition system is working just fine (accept my PIP signal is 5V rather than 12V), and I can communicate with MS-II just fine. The trouble I'm having involves the injectors. They are not grounding through MS-II like I expected they would (I have no fuel spray). I've checked for voltage at the injector connectors. I've got battery 12V on on side and 3V to 4V on the other. I'm assuming the 3V to 4V is just parasitic voltage from MS-II, however, I may be wrong. I haven't worried too much about current and resistors because I'm using the relay board with 10 Amp resistors for the injectors. My ground from the relay board is very solid, and as far as I can tell that's where MS-II also grounds it's self so I don't have a seperate ground for MS-II. I've double check tht the jumpers on the main board are in the proper positions, and they are. I've looked at Megatune settings so many times my it hurts to think about it. I haven't looked into the .ini file settings much, but I don't think there will be any issues there casue I haven't done any code editing (accept for choosing the settings when setting up Megatune and they are correct). I also haven't hooked up my Stimulator. I'll be doing that later this afternoon to see if I come up with anything. This is my first time installing Megasquirt and even though I've been farely diligent in my studying, this one's got me stumped. Any constuctive suggestions would be greatly appriciated.

Thanks

Loki73

[wojeepster]

4v on the other side is wrong and denotes a bad ground or problems with the injector driver transistor to my way of thinking. I do not think Injector will not operate on the 8v that is left. if it is not grounded you should measure 12v on both sides of the injector. Now another silly question. Is your fuel pump working? I mean could it possibly be that the injectors are opening but there is no fuel there because no pump? You can listen to injector with screwdriver touching and to ear, mechanics stethescope, etc. You can hear it clicking if it is operating. I am assuming you are using resistors because you have low impediance injectors, correct?

If you haven't read it Tracy Martins, "How to diagnose and repair automoblile electrical systems" is a good read. While not specific to MS it has helped me alot.

[Loki73]

Concerning the voltage at the connectors I agree that it's not quite right. To be more specific, one wire on the connector should have 12V or battery voltage and the other side (when disconnected from the injector) should be 0V. If it was connected to the injector it would read 12V on both sides only when grounded through MS-II. When the injector is not being grounded then there would be 12V on one side and 0V on the other. Regarding your question about my fuel pump. Yes my fuel pump is working, and there is fuel in the lines. I have a permanatly mounted gauge that shows me what fuel pressure I'm running as well. Besides that, when using a relay board the fuel pump and injectors are on seperate curciuts.

[insanezane]

You can't really check injector voltage with a meter its a fast switching action on and off you need a scope or a light. There is a special light that will pull into the injector plug on your harness or you can wire in your own but you will have to turn the motor over to see if it is firing the injectors or not the light will light dimmly on and off as you get injector pulses. zane

[wojeepster]

Noid light, or logic probe with pulse.

[Loki73]

I've used a scope and a noid light. The injectors are not firing because they are not being grounded because there is something wrong with the MS-II system, not because I'm using the wrong tools.

[insanezane]

well thanks for the aditude good luck finding help

[wojeepster]

When injector is grounded there should be 12v on one side of the injector a 12v voltage drop across the injector and 0v on the other side (assuming no resistor) with resistor added in series the voltage drop across the resistor and the injector should add up to 12v grounded. With the injector not grounded you should measure 12v on BOTH sides of the injector. If there is not a complete circuit there is no voltage drop (and ANYWHERE on the power side of the circuit will measure 12v).

[Loki73]

Thankyou for the correction. I wasn't very precise with my description. Do you have an idea of why my injectors wouldn't be grounding like they are supposed to?

[wojeepster]

will the simulator show you if they are working? If they aren't then I guess it is a matter of checking each component in that part of the circuit board until you find the defective one(s) Does everything look ok? Alot of times stuff that looks burnt is NG. How do the solder joints look? If you see any that look questionable reflow them.

[Loki73]

Yes, everything looks great. DIY did a great job with assembly. Concerning the Stimulator (Jim Stim) the injector LED's only blink for a split second when I first turn it on. Another thing that is weird is that I have no RPM reading when looking at Megatune but I can see the LED on the Stimulator blink/flash. Also, the O2 sensor only registers once in Megatune when I turn the Stimulator on. However, the O2 sensor works properly on the stimulator. To my knowledge I should be able to see the adjustments in Megatune when adjusting RPM, and/or O2 readings, while there is voltage to the board. Am I wrong in that belief?

[Loki73]

I'm running MS2 BG Firmware 2.687.

[Loki73]

Thanks to Matt at DIYAtuotune.com the issue has been resolved. Aparently all that was needed was for me to update my firmware and software.Thanks for the help Gents.

Loki73