[SOLVED] Starts sometimes, wont start other times? (Crank position sensor)

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sacredmonkey92

Greenie N00B Member
Having this weird issue with my speed3. Sometimes it does not want to start (takes probably 20 seconds).
It is a 2008, 146k, stage 3 from cobb (all hardware and tune). I just went outside to go for a drive and it started right up. Yesterday I went to take it to work and I couldn't get it to start. I can post a video if needed, but it will crank, crank, crank, then stop, then crank again. It has a new starter and battery as well. I datalogged on my ap and the only weird thing is that the hpfp is showing 0 voltage.
 
New update, i was going through my datalog again because this is really stumping me. I got the car to start and the mg/cylinder for injector quantity went from 10 when it first fired off to around 1/2. But when I turned the car off and then tried to get it to start again (which it didn't) the injector quantity was stuck at 10 which is leading me to believe it is flooding out the engine. Anyone solve a similar issue? also my injector ground is grounded right to the battery.
 
I think I uploaded my datalog, sorry there's so much info on it I wanted to see everything that was happening. So at first the car starts right up, the key was on for a few minutes and thats why the pressure is a little low. But once I turn the car off and try and turn it back on it just cranks. injector pulse width looks like they are completely open.
 

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I would be curious to see a log of it cranking but failing to start. See if fuel pressure is for some reason dropping, or if anything else jumps out. Could consider replacing or sending your injectors out for a cleaning if you suspect they're the culprit. I don't offhand know what the battery voltage should be showing while cranking.
 
SharksInSpace said:
I would be curious to see a log of it cranking but failing to start. See if fuel pressure is for some reason dropping, or if anything else jumps out. Could consider replacing or sending your injectors out for a cleaning if you suspect they're the culprit. I don't offhand know what the battery voltage should be showing while cranking.
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here is a log of it cranking and failing to start. For some reason I think the battery might have something to do with it. Low voltage can do some weird stuff. I always have it on a trickle charger so it might make sense that it will start right up the first time. Maybe a dead cell?
 

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Completely different car and circumstances, but my mother just went through a no start ordeal that ended up being a bad cell in her less-than-one-year-old battery, so it's possible. Next time you get it started, eyeball that voltage to see if it's charging; could possibly be a bad alternator and maybe your trickle charge is giving it just enough to get it going after being hooked up for a bit.

Or, as was my case, check over the cables to/from the battery to the alternator and ground. The positive side from the alternator on my 2010 corroded to the point of not carrying sufficient charging current and one morning after getting to work, I went to restart the car (literally a minute after shutting it off) to move off an ice patch I'd inadvertently parked on and although I still had lights, stereo etc, the car absolutely would not crank. That was a "hey it's fine" to a sudden straight-up no crank no start no way no how, though, and not an intermittent issue like yours.

ALL THAT SAID, it looks like your hpfp actual was hanging out at about 1k, give or take, during the crank/no start datalog. In the other log where it did start, fuel pressure jumped to 1700s at fire and then settled into idle. I have no idea if that's relevant -- i.e. did the pressure previously jump because of and only after it successfully fired, or did it later not fire because sufficient pressure wasn't achieved -- I don't honestly know. But it is possibly something to look into.
 
Alright sorry for the late response I haven't driven the car much lately. But I put a optima red top battery in it and it did the same thing. After sitting a few days I started it to take it to work and it fired off first turn and then about 3 hours later I went to start it and it took a good while to actually start. Great. Car is charging as well at 13.8-13.9v. I'm getting it tuned by a local shop in a couple weeks, I hope it helps. I'm going to clean off all the ground connections as well.
 
Cleaned off all the grounds, I think it has something to do with the hpfp. Right now when i try and start it my accessport is telling me im just getting a little over 800psi. Maybe I put the internals in incorrectly? It's quite straight forward, we shall see.
 
SOLVED::: got a new crankshaft position sensor and it solved all my problems.

Is there a way to change the name of the thread so I can put solved so people who may be having the same issue can check it out?
 
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sacredmonkey92 said:
SOLVED::: got a new crankshaft position sensor and it solved all my problems.

Is there a way to change the name of the thread so I can put solved so people who may be having the same issue can check it out?
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Glad you got it fixed, I added [Solved] to the thread title
 
sacredmonkey92 said:
thanks a lot! she purrs like a kitten now! a very gnarly kitten but she purrrrs
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Fuck i ordered mine i was having the same fucking issue to where i feel like burning the enhine bay...sorry tht was my head talking..but damn glad u ahare this info crankshaft positin sensor coming in 3 days from now
 
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