Injector driver blown?

[Semi P-port]

I have a 13b rotary engine that I'm using MS1 v3 on to control just the fuel and triggering off the negative of the coil. I have been having troubles getting it to start lately and I think i have found the problem. I found out that the injectors squirt wide open all the time flooding out the engine and keeping it from starting or running. I opened megasquirt and found that R12 looks a little burnt so I tested it's resistance but it was 3.9 ohms. So now I think I might have screwed up the injector drivers some how. Could someone please help me with a list of things to test and how to test them (Like Q1 and U7) so I can find out what is exactly wrong. I'd really appreciate any help! Thanks, Joe

[Matt Cramer]

R12 should be 390 ohms - you may have had the multimeter on the wrong setting there.

First thing I would do is put the ECU on a Stim and power it up. See if the injector LEDs come on. Then remove the processor and repeat this test. If they're still on, check the voltage at pin 1 of Q1 and Q5. If the voltage is near zero, remove the FETs and see if the injector lights go out. Let me know what you find.

[Semi P-port]

Yeah sorry I meant 390 ohms. Ok, i will check all of that. By processor do you mean U1 or U7? The Led's do come on when it's powered up. They come on for about a sec then turn off

[Semi P-port]

EDIT: Only the middle Led comes on when powered up. The Led doesn't come on with U1 removed and ms powered up. I checked voltage on Q1 and Q5 and there was around 2.3 volts on the middle pins of both of them, but the two outer pins had no voltage. Also the injector led will flash when 12v is applied to pin 24 (ign pin). I am using 4 low impedence injectors (resistance is 2.3 ohms). Two of them are wired to injector bank 1 and the other two are wired to injector bank 2 if that helps any.

[Matt Cramer]

The processor is U1. Do the Stim's injector LEDs stay on when the processor is in place?

[Semi P-port]

Well I plugged the stimulator into ms and it looked like all the lights lit up correctly so I plugged it into the laptop to see what it was doing on Megatune and it was fine untill I turned the rpm up past 400 and then it went crazy. It was like megasquirt was turning on and off repeated and all the values were going crazy. What could that be?

[Matt Cramer]

Do you have a data log of the "going crazy" behavior you could post?

[Semi P-port]

Well, I flashed the ms1 code into the processor after it did that and it started acting correctly again, so I hooked it up to the car and got the car to idle if I worked the throttle and could get it to rev up some times, but it was still really rich and it seemed like the adjusting I did didn't make much of a difference. I ordered some parts from DIYAutoTune (U1,U7,Q1,Q5,Q9,Q12,R12) to replace and see if it helps or fixes anything. Is there any other parts I could check or replace?

[Matt Cramer]

Mostly that sounds like it needs more tuning, unless the injectors are outright stuck open.

[Semi P-port]

Well the pulsewidth showed around 8ms and the duty cyle showed 10-12% in megatune while trying to keep in idling which seems about right for my set-up I would think, but the car was still super rich. I tried turning the required fuel down to around 6ms and it was still really rich(fuel out the exhaust) and ran just the same. I also switched it over to Alpha-N since my map value doesn't go under 70. The car is about 10 miles away at a friends house so I will try tuning on it some more this weekend and see what happens. Thanks for all the help

[Semi P-port]

I did some tunning on the car this weekend and it seems like the changes I'm making don't effect the way it acts at all. The car will hit and start fairly quickly but immediately die or go back to cranking. The car also is very rich and has fuel coming out the exhaust when cranking or running. If I work the throttle sometimes I can get the car to idle around 600-700 rpms and sometimes get it to rev up. The injector lights on the stimulator light up correctly when connected to megasquirt and when all the pots are turned. Could the injectors themselves gotten screwed up somehow? Thanks a bunch for helping me figure this out! it's got me completely stumped!

[kjones6039]

Are we talking RAW fuel here?

[Semi P-port]

Yeah . I'm wondering if my ignition or my injectors aren't screwed up somehow.

[Slave2theBunny]

I just wanted to know if you figured out this problem, I'm having the exact same problem, injectors stuck wide open with the key in the ign position with the car off.