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Old 12-21-2012, 02:47 AM   #1
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Default hot starting issue, somehow relay/electrical connected

Something is wrong with my electrical system and I have no idea what it is.
car starts fine if it has been sitting. and usually if i stop to get gas it starts fine. but if i have turn it back off a second time it wont start again. but it has never once left me stranded at school or at home where it has been sitting for a few hours. only if its been turned off for a few minutes or so.

back story about the problem
so few months ago the car decided to leave me stranded would sit there and crank but nothing. realized that under the hood and at the ecu i was only getting around 4 volts and found it was the main relay (b5b4) under the hood I replaced it with a bap unit and worked great for a week and it did it again, and found out the insides were not oem it seemed to be some circuit board digital contraption instead of the oem relay's coil and arm.
so i replaced it with the 70 dollar OEM one from mazda worked for nearly a month. since then I have been keeping the relay on life support by avoiding hot starts, (turbo timer is awesome for when i go in to the gas station)
or i can either pull the relay and jumper the two terminals a few times replace the relay and it will start.

What i have noticed since i installed the mazda relay is the relay arm makes good contact, coil is energized fine and pulls the arm VERY firmly all the terminals look clean and the relay's terminals look clean.
if jumpering once doesnt usually do anything. if i do it a few times (varies) eventually i can hear another relay or something else somewhere else under the engine bay energize and click. when i hear that i can plug in the relay again get in the car and it will start up fine. (stumbles a second and smells a wee bit rich but goes to normal before my wideband even heats up in <5-7 seconds and can give me a readout)
this makes me believe that the main relay isnt the culprit. but something else somewhere else. maybe that unknown clicker?

a month before all this I installed the hydra/injectors, 2 weeks before that water meth, and 2 months prior. stereo, and boost controller. all of which work fine even when the relay is acting up. so i am also doubtful that these are contributing but i could be wrong. hydra being the most recent yet still a month before the issues started happening.

So now I am beyond my abilities and dont know where to look. and I am hoping that maybe one of you know what is going on.
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Old 12-21-2012, 11:27 AM   #2
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Just out of curiosity, have you replaced the coolant temperature sensor on the back of the motor? That's the one that feeds the ECU and if that thing begins to fail it gives the same problems you are listing here.
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Old 12-21-2012, 12:35 PM   #3
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Need more info!

What year car, motor, harness...

Have you load tested the battery, or tried another one all together?
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Old 12-21-2012, 02:45 PM   #4
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2004 mazdaspeed, so 1.8bpt harness is stock other than the pnp patch harness going to the hydra.

haven't checked the coolant sensor hell didn't even think that would be related but i can try.

battery is good, hasnt been loadtested but shows 12 volts and ive had to crank it off and on for 3-4 minutes untill i learned that i had to wait for that second *click* from under the hood.
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Old 12-21-2012, 03:24 PM   #5
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When you turn the system back on and attempt a hot restart, what do the IAT and CLT sensors read?

What fuel PW is the hydra putting out during cranking?

There's really nothing electrically that would prevent the car from starting when hot while still allowing the ECU to turn on. My bet is that this is a software configuration issues.

MAYBE the fuel pump isn't coming on, but you can check that just by unscrewing the fuel filler cap and sticking your ear on the hole while someone else turns the key.
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Old 12-21-2012, 08:27 PM   #6
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well the ECU isnt completely coming on. when the problem happens the ecu is only getting about 4 volts vs 12 like normal..


and i would tell you all the iat, clt, fuel etc. but unfortunately I need to get a new serial to usb cable. my computer doesnt recognize it something is loose inside it i believe because it either wont work. or i can get it to work and then randomly disconnects. whereas my tuner friend can hook in perfect with a normal serial cable.
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Old 12-26-2012, 04:08 AM   #7
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Did you read this reply to your other thread?


Jeremy sent 2.7 owners some news:

"There was a problem that it took us a while to sort out that I wanted to talk about. Some cars running NB triggers (1999-05) were having a problem where after they heat soaked, the cam sync signal started becoming erratic & the engine would no longer run smoothly. This could be confirmed by running a Tools -> Trigger Test while the bad behavior was occurring & looking at the cam sync trace. For a few owners it was so bad that the car wouldn’t run. I think I have identified & corrected the problem for all those folks. For some others though, it may show up as a random singular misfire that happens now & then while you’re cruising along with no good explanation. What is happening is an issue with tolerance stacking & resistance buildup from heat causing a 5.1v protection diode to run too close to the edge of the ~5V cam sync signal. The solution is to send your ECU back to Hydra & they will replace it with a 5.6v protection diode. A few guys have already had this done & I know who, so if anyone else experienced these issues (probably when it was hot out still) let me know & I can get you a RMA# to send your unit in for the fix. This is a relatively small portion of the owners, so if this description doesn’t make you go “oh yeah” don’t worry about it. In other words, if you don’t have the problem don’t send it in. In addition Hydra will not tell you how to do it & if you try it yourself it will void any warranty you have"
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Old 12-28-2012, 12:11 AM   #8
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Quote:
Originally Posted by Dange View Post
well the ECU isnt completely coming on. when the problem happens the ecu is only getting about 4 volts vs 12 like normal..
Ah, I missed that part.

To be clear: if you measure the voltage on the white/red wire at the ECU relative to ground, you are reading ~4v when the system is in this state?

I honestly can't come up with a theory to explain this. The main relay is about the only active component between the battery and the ECU, but I can't imagine how you could make it cause this extremely specific failure.
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Old 12-30-2012, 10:27 PM   #9
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Screaming. I was one of the main people that brought that "recall" into light. my first hydra would start up and then just start misfiring so bad i was leaking gas out of the exhaust. it almost always started just fine.
this was when jeremy still thought it was just my sensor. or a faulty install.
I actually had to stop at flying miata for jeremy to test my ecu. and as soon as he plugged in a new box the problem was gone. so he RMA'ed it and just gave me a new one off the shelf.

and joe thats exactly what I am thinking. I am at a complete loss. the ecu, tested with jeremy walking me through it on the phone, all the sensors under the hood that should be reading 12v everything was getting ~4 volts. so we thought it was the relay, and why ive replaced it twice. but then finally realized it never left me stranded in the morning. so it couldnt have been the relay.
but my stereo/lights/starter/etc were all getting the normal voltage.

I am going to test it again next time it happens. double check the voltages and then try to keep cycling the main relay so i can listen for that click and try to pinpoint it.
I will also probably just buy a new walbro and fuel filter JUST incase im missing something or maybe the stocker is dying and not turning on or shorting out.
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Old 12-31-2012, 12:10 AM   #10
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Quote:
Originally Posted by Dange View Post
(...) JUST incase im missing something or maybe the stocker is dying and not turning on or shorting out.
Don't go messing with random parts until you locate the root cause of this low-voltage symptom. If the fuel pump (or anything else, for that matter) was drawing enough current to pull the system voltage down from 12v to 4v, something would be on fire.

... unless some part in the path of the white/red circuit was failing in a way that it exhibited an abnormally high resistance, which is about the only thing that can possibly be causing this symptom.


... but why it would only do this after the car is power-cycled while warm defies any rational explanation I can think of.


... which doesn't mean that there ISN'T a rational explanation, merely that I can't think of it.
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