[SOLVED] Need help please! Random no start!

Mahzy

Greenie N00B Member
2012 Mazdaspeed3
So, I park my car in my garage to do some maintenance.
1. Change valve cover gasket
2. Change Plugs
3. Change oil and filter

so, first thing first, I disconnected the battery just out of habit. Pulled the plugs, then valve cover. Replaced plugs, and taped off and put a coat of paint on the valve cover. (I sanded down everywhere a screw goes in to be safe for random grounds)Replaced the gaskets and re-seated the cover. Tightened the cover down, reconnected the boots and connectors that had to be unplugged (cam sensor) so all is back to how it needs to be. Next, simple oil change, then reconnect battery. Now car is fully back to exactly how it was when parked except, new plugs, oil, and better looking valve cover.
now, the car will not start but will turn over and some tries catch for a split second but leads to nothing. There is spark, all sensors are working. LPFP hums, the only thing I do not know how to check or address is the HPFP.
Any and all help welcome because I’ve been at this for 2 days and a lot of money in replacing any and everything. Thanks!
 
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To be clear it's cranking over but won't catch?

I feel like there's a missing connection somewhere after the job probably something Silly. There's a harness on the front left side of valve cover when looking at it and then some connectors on the right side by hpfp.
 
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Can you pull the TMIC (if you have one...sorry, can't see your mods or signature using the phone) and take some pictures of everything for us?

To add to what @Awafrican posted, check each and every connector you disconnected and reconnected to ensure it is fully connected. I once had a rough idle and CEL start when I disconnected and reconnected the MAF wiring harness for routine maintenance. It didn't seat correctly the first time I reconnected it.
 
In order to pull the valve cover, don't you need to unplug the crank angle sensor? IIRC it drapes over the valve cover and hangs out with the alternator power cable.

Edit:
How did you check for spark?
 
If he has spark and fuel, probably not as it would have fired. If he has fuel but no spark (he says he has spark) then yeah.
 
Do you have a scanner, or just a code reader. You need to check if the ecm is seeing the cam sensor. There isn't too many things there that would cause that. Make sure that the wires haven't pulled out of the Cam sensor plug. Pull the sensor and check for anything on the sensor itself. Ensure that the two plugs on the drivers side above the HPFP are seated, and no pins loose or pulled out.
 
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Check all your fuses first. Make sure all of them are good. If you pulled a wire or shorted something then a fuse could have popped.

Next check all your connectors and make sure they are fully seated. How did you test for spark? Did you pull a plug and crank it to see the spark or did you use a spark tester inline between the coils and plug. Did you check spark on every cylinder?

As stated above pictures would help.
 
Is the starter working? It is common on these cars for the signal wire to the starter to corrode causing it to work intermittently. You also have to make sure when you painted the valve cover that this entire area is paint free for the cam sensor.
upload_2021-3-16_8-39-13.png
 
^^ Yep. If that surface where the cam position sensor sits is painted, you'll have issues
 
I have read all your replies and I have tried each and all of them. No codes, reconnected all wires many times along with checking them with a multi-meter to make sure they have power. As stated, all screw holes on the valve cover have been taped or taken back to bare metal, the sensor in question I replaced because I thought that was the issue as well. Stater is working, there’s just no explanation to why it’s not starting. It’s a full stage 3 ms3, just no accessport. Thank you everyone.
 
What size intake? If larger than stock with no tune. Its not gonna run.

If you need to move it, you can unplug the maf and it'll run for a little bit
 
I’m not sure what pictures are needed to help you guys out, there is spark, I tested by just pulling the plugs and placing them in the boot to see spark, they all work. Tried 3 sets of plugs to be sure. All the fuses are good and checked with a multi meter and as stated in the starter post, the battery was disconnected the entire job out of habit to prevent any of this from happening.
 
What spark plugs did you use and have they been gapped correctly?

Pictures of your engine bay would also be super helpful, just in case there is something you may have missed.

EDIT: basically, pictures of all the harnesses, etc. Have you checked to ensure you battery is fully charged...it's amazing the electrical gremlins that a bad battery can cause, even though it appears to be working.
 
Sho said:
What size intake? If larger than stock with no tune. Its not gonna run.

If you need to move it, you can unplug the maf and it'll run for a little bit
Click to expand...
Same size intake as it was when I parked it to do the job. Nothing is new, ran when I parked it now it won’t
 
Duey1083 said:
What spark plugs did you use and have they been gapped correctly?

Pictures of your engine bay would also be super helpful, just in case there is something you may have missed.
Click to expand...
Spark plugs are the same brand and gap as the old ones, plus won’t fire on the old plugs either. Pretty sure they are Denso Iridiums because nobody around me carried the ngk so I’ve just been running the denso’s. As I said, same plugs the car already ran on
 
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