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Vancouver Auto Chat 2016 VAC Community Head Moderator: Raid3n

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Old 01-02-2011, 04:52 PM   #1
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Local Megasquirt guru I need your help tonite

http://www.miataturbo.net/showthread.php?t=54710&page=2

see last post.

Basically the trigger ground wires on injectors 2/4 are grounding in the MS box somewhere the minute I turn the key to ON causing the injectors to lock open and flood my engine. I need my car running by tomorrow to get to work. If anyone here is proficient in MS and the associated circuitry I will buy you beer if you can find what is grounding inside my MS1 box tonight.

I've tested continuity at the injector clips to the chassis and it does not ground when the key is OFF or the MS1 box is not plugged in. Making me come to the conclusion that it is not a wiring issue (I've never touched the wiring in the car anyways) and it only grounds when the MS1 box is plugged in and the key is in the ON position.

My number is 778 847 0947. Call me if you can help.


Quote:
I just checked again to be sure. With the ignition OFF, I get zero readings on all four clips on the ground wire to the chassis.

With the key in ON, I get -.19 on clips 2/4 and zero reading on clips 1/3.

So that would make me belive that the grounding issue is not in the chassis wiring or it would give me a reading regardless if the the car was set to ON or OFF? Since it only gives me a continuity reading when the key is ON, that means it's something inside the box? Am I right in thinking this? Also, if the grounding issue was in the wiring, then the injector would be completing a circut even without the MS box in the car when the key is in ON? Since it dosen't do that, again... makes me belive the problem is in the box not the wiring.

I got a reading from Q3 to injector 2/4 pins on my board while checking continuity. No other pins gave a reading except the middle one on Q3.


PIN 32/33 are the ones that are grounding which should not be.

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Last edited by falcon; 01-02-2011 at 05:07 PM.
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Old 01-02-2011, 05:05 PM   #2
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Just one beer ? Sorry wish i could help
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Old 01-02-2011, 05:05 PM   #3
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beers. plural.

I've done most of the diagnosing, I just need someone who actually knows electronics and who knows where to look on the board to fix what's wrong.
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Old 01-02-2011, 05:25 PM   #4
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oh i thought it was some sort of a water gun fight tonight i was like "damn thats going to be freezing", forgot there was some car thingy named that
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Old 01-02-2011, 05:59 PM   #5
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I have a wiring schematic. Should make life easier. Trace back ont he board and find what's grounding..

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Old 01-02-2011, 06:03 PM   #6
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Old 01-02-2011, 06:07 PM   #7
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Quote:
Originally Posted by falcon View Post
beers. plural.

I've done most of the diagnosing, I just need someone who actually knows electronics and who knows where to look on the board to fix what's wrong.
Good luck finding someone Falcon, if I knew anything about megasquirt systems happily lend you a hand, car problems on a Sunday night are the worst.
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Old 01-02-2011, 09:40 PM   #8
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Transistors Q1 and Q5 are the output transistors, not Q3 (which is part of the flyback circuit along with Q11).

There are a couple possibilities, and I'll list them with the most likely ones first.

- The transistor Q1 is bad (I have seen this happen a lot more often than you'd think).
- The driver circuit to turn on Q1 is bad causing it to activate when there is power applied (ignition ON). There is an 8 pin IC that is used as a MOSFET driver which provides the proper signal to turn on the output MOSFET.
- There is something wrong with the circuit board (like a bad solder joint or debris connecting two traces together).
- Your microprocessor is bad sending a high output to the MOSFET driver.

This is all assuming that there's no problem with your configuration of the ECU and that your firmware is not corrupt.
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Old 01-02-2011, 10:08 PM   #9
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Sorry man, just got your PM a few minutes ago otherwise I'd have helped out earlier.

As Dangonay mentioned, I'd suspect something with the Q1 transistor (he's gone into detail so I wont repeat it). The other thing that might be wrong is your CPU itself. I was having issues with a couple components not turning off when they were programed to, despite the fact that all of the settings inside MS were correct and all the connections were clean. I swapped it out with a new CPU, flashed the exact same settings into the new chip and suddenly everything worked fine. This happened to my buddy's system as well. It's not a common problem, but it does happen... though I'm not entirely sure why.
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Old 01-02-2011, 10:18 PM   #10
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No problem. I acutally ended up driving down to Bellingham to the guy who built it and we traded ECU's with his known working one. Same build specs. He is going to look into it tomorrow.

Now the worse news. I put his ECU in (same build) flashed my MSQ onto it, cranked... and FUCK. Fully hydrolocked the engine. Worse than before and this timm on all 4 cyl.. they are PACKED with fuel. The only explanation I can think of is the TPS wires shorted causing the engine to lock all 4 injectors open. I hand cranked the engine over with the spark plugs out and it was like the floodgates were open. There was even fuel dripping out of my intake filter.

So tomorrow I need to change the oil, get the fuel out, trace the TPS wires back to the ECU and terminate them at the ECU to verify they are not shorting. Note* that I don't run a TPS. It's unplugged.
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Old 01-02-2011, 11:21 PM   #11
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Quote:
Originally Posted by falcon View Post
No problem. I acutally ended up driving down to Bellingham to the guy who built it and we traded ECU's with his known working one. Same build specs. He is going to look into it tomorrow.

Now the worse news. I put his ECU in (same build) flashed my MSQ onto it, cranked... and FUCK. Fully hydrolocked the engine. Worse than before and this timm on all 4 cyl.. they are PACKED with fuel. The only explanation I can think of is the TPS wires shorted causing the engine to lock all 4 injectors open. I hand cranked the engine over with the spark plugs out and it was like the floodgates were open. There was even fuel dripping out of my intake filter.

So tomorrow I need to change the oil, get the fuel out, trace the TPS wires back to the ECU and terminate them at the ECU to verify they are not shorting. Note* that I don't run a TPS. It's unplugged.
That's rough man. Good luck.
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Old 01-02-2011, 11:56 PM   #12
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all these gay blowjob and squirtgun posts should be removed or at least failed by the masses. youd think in the AUTOMOTIVE chat people would try to help or not post instead of being children. "TEE HEE he said mega squirt! tee hee!" the guys looking for some serious help here

if you want to talk about your megasquirting problem take it to OT or the NWS forum, or i guess the relationship forum.
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Old 01-03-2011, 01:16 AM   #13
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Quote:
Originally Posted by falcon View Post
The only explanation I can think of is the TPS wires shorted causing the engine to lock all 4 injectors open. I hand cranked the engine over with the spark plugs out and it was like the floodgates were open. There was even fuel dripping out of my intake filter.

So tomorrow I need to change the oil, get the fuel out, trace the TPS wires back to the ECU and terminate them at the ECU to verify they are not shorting. Note* that I don't run a TPS. It's unplugged.
TPS doesn't make sense to me as a problem. It's simply a voltage input directly to an ADC on the processor, and it has a resistor inline to limit current in case of something like a short circuit. The other two wires for the TPS are 5V VREF and ground, and the VREF is protected with a resettable fuse.


If his ECU works for sure, and now you have all 4 injectors (both channels) dumping fuel, then I think you've got an issue with your software/MAP. I just don't see how any sensor input, no matter how far out, could case the ECU to make a decision to open the injectors up and dump that much fuel.
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Old 01-03-2011, 01:45 AM   #14
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The TPS on my car is not variable. It's only open or closed. There is no VREF signal or there may be, but it dosen't work the way you were describing it. The same thing happened to a friend of mine on his car with MS. His TPS wires shorted on each other and caused his injectors to lock open. The way I understood it, was if the TPS shorts into the "open/WOT" position it makes the ECU think your WOT and tells the injectors to open.

I'm lost as well. I'm going to rule out the TPS wires tommorow and then try to start it again. My MAP is exactly the same as it's been since May. I haven't made any changes to it. So for this problem to come out of the blue is just odd.

And yes, his ECU works fine. He pulled it out of his running car for me to take home.
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Old 01-03-2011, 02:01 AM   #15
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^ So you have the TPS input set up as a WOT switch input?

Still, I never would have expected the cylinders to flood over that. WOT shouldn't mean "injectors on all the time" so much as it should run the injectors at their maximum duty cycle. The operative words here being "duty cycle" - you can't have an injector firing if the engine isn't running/cranking meaning the injectors shouldn't ever be on simply because your ignition is on.
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Old 01-03-2011, 02:17 AM   #16
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Ya I know. I get everything you're saying, which is why I'm at a loss as to where to look next. The TPS input on the board is set up for a variable sensor however it is not being used right now. The wires terminate at the unplugged connector in the engine bay.
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Old 01-03-2011, 02:40 AM   #17
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I knew Lomac would be in here, he's megasquirt king!

that and, everytime I hear the name, I always think of a bad porn name...
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Old 01-04-2011, 01:04 AM   #18
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Quote:
Originally Posted by RRxtar View Post
all these gay blowjob and squirtgun posts should be removed or at least failed by the masses. youd think in the AUTOMOTIVE chat people would try to help or not post instead of being children. "TEE HEE he said mega squirt! tee hee!" the guys looking for some serious help here

if you want to talk about your megasquirting problem take it to OT or the NWS forum, or i guess the relationship forum.
Technical Discussion Forum

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it's not like we're taking away from him getting help either


(forgot i wanted to reply to that, thought id wait till Falcon was through before leading this anymore off-topic) :P
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Old 01-04-2011, 04:48 PM   #19
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I put it in here so it would catch someone's eye. Someone who dosen't go in Tech discussion. Deal with it.
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Old 01-04-2011, 05:17 PM   #20
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my comment had nothing to do with u falcon (it was to rrxtar)


it was to point out that since this is the "Chat" area commentary in the form of a chat should be expected i.e. jokes, quips, etc.

since we are a community and it is the chat area friendly chit chat should be expected (in the chat area)
if you want to bitch out chatting in the chat area we could flip that around and have bitching over posting in the wrong area (its only 'the wrong area' because you're demanding 100% serious replies).


Now in regards to you; if what i just noted above is not something you wanted or expected you should have known better, so to quote you "deal with it".

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Old 01-04-2011, 08:05 PM   #21
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Or, people could realize it's a serious thread and refrain from posting silly comments.

Regardless, it helped and it is what it is.
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