Engine cranked backwards by hand won’t start

Jiggy370 · 09-11-2022, 12:29 PM

So my friend and I were doing a new flywheel and clutch install. Whilst we were reinstalling the transmission we were cranking the engine from the front with a socket and breaker bar so the splines would line up with the transmission. My friend lost his footing and cranked it backwards a decent amount. We thought it might be okay at the time but as soon as the job was done we went to start her up and the car was turning very confidently but we couldn’t get it to spark. After a bit of reading I think turning the crank backwards offset my cam timings hence why we can’t get it to start. Any advice on how I can go about fixing this or anything else I can look into is really appreciated.

ZoomZ · 09-11-2022, 12:59 PM

Engine should not throw out Cam timing because you turned it backwards slightly. If ti did, that's one shitty design. Only thing I can think of is, if you had loose parts in timing chain components. I can see a Timing BELTS slipping but not chains that go over gears. Not saying its imossible.

Anyway, the last human interaction with a mechanical object was with YOU and the clutch/ flywheel install. There is a front and back to the flywheel, and there are teeth that mate to a sensor for crankshaft position.

Check your wiring and re trace your install steps.

ZoomZ · 09-11-2022, 01:17 PM

Check for deformation or damage of drive plate (A/T models) or flywheel (M/T models).
CAUTION:
• Never disassemble drive plate (A/T models) or flywheel (M/T models).
• Never place drive plate (A/T models) or flywheel (M/T models) with signal plate facing down.
• When handling signal plate, take care not to damage or scratch it.
• Handle signal plate in a manner that prevents it from becoming magnetized.

Flywheel (M/T models)
• Ensure the dowel pin (1) is installed in the crankshaft.
4 : Rear oil seal
• When installing flywheel (3) to crankshaft (2), be sure to correctly
align
crankshaft
side dowel
pin and flywheel
side dowel
pin
hole (A).

It's been done incorrectly before!

ZoomZ · 09-11-2022, 01:40 PM

I would start by checking the Crankshaft position sensor wire/harness/connector.

phunk · 09-11-2022, 02:44 PM

^ agree. Crank sensor/trigger wheel issue.

09-11-2022, 12:29 PM	#1 (permalink)
Jiggy370 Base Member Join Date: May 2022 Location: Ballarat Australia Posts: 2 Drives: white 2010 370z Rep Power: 3	Engine cranked backwards by hand won’t start So my friend and I were doing a new flywheel and clutch install. Whilst we were reinstalling the transmission we were cranking the engine from the front with a socket and breaker bar so the splines would line up with the transmission. My friend lost his footing and cranked it backwards a decent amount. We thought it might be okay at the time but as soon as the job was done we went to start her up and the car was turning very confidently but we couldn’t get it to spark. After a bit of reading I think turning the crank backwards offset my cam timings hence why we can’t get it to start. Any advice on how I can go about fixing this or anything else I can look into is really appreciated.

09-11-2022, 12:59 PM	#2 (permalink)
ZoomZ Track Member Join Date: Jan 2017 Location: Vancouver, BC Posts: 761 Drives: 17' 370Z Nismo Rep Power: 40617	Engine should not throw out Cam timing because you turned it backwards slightly. If ti did, that's one shitty design. Only thing I can think of is, if you had loose parts in timing chain components. I can see a Timing BELTS slipping but not chains that go over gears. Not saying its imossible. Anyway, the last human interaction with a mechanical object was with YOU and the clutch/ flywheel install. There is a front and back to the flywheel, and there are teeth that mate to a sensor for crankshaft position. Check your wiring and re trace your install steps. filip00 likes this.

09-11-2022, 02:44 PM	#5 (permalink)
phunk A True Z Fanatic Join Date: Mar 2009 Location: Chicago Posts: 3,668 Drives: 370 Rep Power: 974723	^ agree. Crank sensor/trigger wheel issue. __________________ Charles @ CJ Motorsports : Website \| Facebook \| Instagram \| YouTube Home of the 9 second, stock longblock, stock drivetrain 6MT 370z. 9.91 @ 142mph

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09-11-2022, 01:17 PM	#3 (permalink)
ZoomZ Track Member Join Date: Jan 2017 Location: Vancouver, BC Posts: 761 Drives: 17' 370Z Nismo Rep Power: 40617	Check for deformation or damage of drive plate (A/T models) or flywheel (M/T models). CAUTION: • Never disassemble drive plate (A/T models) or flywheel (M/T models). • Never place drive plate (A/T models) or flywheel (M/T models) with signal plate facing down. • When handling signal plate, take care not to damage or scratch it. • Handle signal plate in a manner that prevents it from becoming magnetized. Flywheel (M/T models) • Ensure the dowel pin (1) is installed in the crankshaft. 4 : Rear oil seal • When installing flywheel (3) to crankshaft (2), be sure to correctly align crankshaft side dowel pin and flywheel side dowel pin hole (A). It's been done incorrectly before!

09-11-2022, 01:40 PM	#4 (permalink)
ZoomZ Track Member Join Date: Jan 2017 Location: Vancouver, BC Posts: 761 Drives: 17' 370Z Nismo Rep Power: 40617	I would start by checking the Crankshaft position sensor wire/harness/connector.