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Old 04-07-2013, 06:56 PM   #1
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Default Megasquirt diypnp wont start anymore

installed diypnp for my 2001 miata and I had it idling nicely and fine, then it stopped starting. It will idle for about a second then die. It runs perfectly fine with the stock ecu. The only thing I can remember changing was under idle settings from 15 minute iac to pwn warmup. Must have ruined my iac valve because it makes no difference in idle with stock ecu, and hums when car is in standby ignition.

Also If i run it for a while on the stock ecu then switch to megasquirt, it will idle for about 5 second...the fuel pump also doesn't turn on when the battery is plugged in with ms...it used to. When I rev it doesn't make a difference to the idle, it must not be getting fuel? Required fuel is still at 13.2 which is how it always was and ran fine.

Last edited by Turbonator; 04-07-2013 at 07:35 PM.
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Old 04-08-2013, 11:45 AM   #2
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Does reloading the firmware and going back to your last known good tune have any effect?
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Old 04-08-2013, 12:32 PM   #3
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I already tried flashing it but I reinstalled the firmware that was previously on there. I tried a different base map.. still doesn't idle. I had wired in a voltage regular for alternator (external)and a wide band o2 but I un wired both of these. The pump used to prime for 2 seconds everytime I attached the battery terminal.

Also there is this red wire comming out of the firewall near the brake booster which is severed. It's possible this was from an alarm system the previous owner installed then removed.

Last edited by Turbonator; 04-08-2013 at 01:37 PM.
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Old 04-08-2013, 04:30 PM   #4
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Also now that I remember there was a buzzing sound when megasquirt was plugged in and the battery terminal was on. The sound would go away when the key was turned, was a decently loud sound.
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Old 04-09-2013, 10:12 AM   #5
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Please post your MSQ and a data log of an attempted start.
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Old 04-09-2013, 12:11 PM   #6
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Heres my files...I tested the r13 resistor and it gets 0v all the time.
Attached Files
File Type: msl why wont u work.msl (62.8 KB, 59 views)
File Type: msq miata natural.msq (83.4 KB, 55 views)
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Old 04-10-2013, 10:08 AM   #7
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Looks like it's getting a good RPM signal. Can you get fuel and spark in test mode?
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Old 04-10-2013, 12:09 PM   #8
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I believe the only thing it is lacking is fuel, something happened to one of the circuits or something because ms was buzzing at one time when I connected the battery cables, but stopped when I turned the ignition key. This was when it stopped working. I believe this was after I messed with the idle control settings.
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Old 04-10-2013, 06:15 PM   #9
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I have some voltages I took

cpu pin 14 to r33 4.9v

50 pin...pin 22 to car ground= 2.5v

pin 22 to car ground=always 2.3v after battery terminal connected

cpu 14 to U8 pin 2=4.9v for about 2 seconds then drops to 2.5v

cpu 14 to car ground=always 4.9v


Shouldn't pin 22's increase while the fuel pump should be running?
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Old 04-11-2013, 10:24 AM   #10
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Will the injectors fire in output test mode?
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Old 04-11-2013, 11:18 AM   #11
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Il take em out and test em but I think they do because everytime I go to start it will run for a few seconds or atleast cough after running with the stock ecu. It runs very normally during this period, then stalls. Pretty convinced it's a fuel pump circuit. Anything else I can test? I'd like to order the part and fix this asap. Remember there was a electrical buzzing sound, any specific component that could have been?
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Old 04-11-2013, 11:29 AM   #12
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take them out to test them?

there's a fuel injector test mode, bro.
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Old 04-11-2013, 11:33 AM   #13
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I'm aware of that, then obviously I don't understand how it would work. I would think it would flood the engine?
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Old 04-11-2013, 11:42 AM   #14
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not if the fuel pump isnt running.
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Old 04-12-2013, 09:29 PM   #15
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Ok, well I tried the fuel pump test mode and the pump didn't turn on. So afterwords I just started it for the heck of it, the map sensor not even connected. And it idled...at 500rpms pretty nicely until Hit the throttle and it immediately died. So I hooked up the map sensor and It wouldn't start. Disconnected map again and it ran..adjusted the idle screw and brought it up 1k rpms. If I hit the throttle it lags but doesn't die, but will died in 2 seconds if I plug the map in, map should be calibrated.

In the log I just let it idle and poke the throttle a few times, and in the end I connect the map sensor.

Fuel pump doesn't prime still, I'm guessing U8 is damaged, as I get 0v before I started it and when im running it at it's output (pin 22). Was told it should be 12v when pumps not running, and 0v when it is.

EDIT: U8 doesn't seem to get any voltage on any pin whether it's running or immediately after battery is connected. Cpu pin 14 mostly 5v, sometimes it goes in between 3.75-4.25, then goes back to 5.
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File Type: msl strange stuff.msl (218.7 KB, 39 views)
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Old 04-12-2013, 10:10 PM   #16
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What's the map read with the car off? You might have a bad map sensor. Suck/blow on the map line to see if it's responding correctly.
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Old 04-12-2013, 10:22 PM   #17
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Map reads 99.5 when engine is off. It responds correctly.
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Old 04-13-2013, 10:22 AM   #18
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so you need to tune?
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Old 04-13-2013, 02:43 PM   #19
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Fuel pump still doesn't turn on...

Update: Ok I've found the source, somehow the fuel pump and IAC wires were shorted.

Last edited by Turbonator; 04-13-2013 at 04:39 PM.
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Old 04-13-2013, 05:56 PM   #20
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Ok, well I removed the relay for the fuel pump and jumped it, and the fuel pump runs just fine. The engine for quite a while if I prime the pump, and the relay isn't plugged in. Still stalls when I plug the map in...U8 mosfet must need to be replaced in order for the pump to activate.
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