Timing belt stripped, replaced, and wont start. Getting spark and fuel
06-09-2017, 10:22 PM
#1
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Timing belt stripped, replaced, and wont start. Getting spark and fuel
My car is a 2005 NB2 with a 1.8 VVT N/A with around 10-15k after a rebuild. It is also running a Reverant MSlabs MS3 and Flow Force injectors.
So yesterday I was cruising along in 5th gear around 3k rpms and my car just died in the middle of the road. I heard a pop, and some clicking, then I pulled over in a parking lot with the momentum I had. When I would crank the car again, it sounded weird, as if it the starter was freely spinning the motor with no resistance. I popped the oil cap off and the camshaft wasn't moving. Turns out the timing belt stripped all the teeth around the crankshaft gear. I replaced it today, put it all back together and it won't start. It is making the same starting noise it was making before. Normally the car has a distinctive starting sound that most Miatas have, it's hard to describe the sound other than its smoother, almost freely spinning. I checked to see if it had fuel and spark, and it had both. The AFR went richer after cranking the car a few times and the spark plugs were sparking. I believe the timing is pretty spot on, but even if it was off a tooth or two, it should still do something, right? At this point I don't know what to do. Tomorrow I'm going to run a compression test on the motor, but I don't really think that's gonna tell me much. Any help would be greatly appreciated.
Next day:
I checked the crank position plate and it is convex out as it should be, and I also replaced the crankshaft position sensor with a brand new one. Checked the timing again, and had a second opinion, looks perfect. Still won't start. Still sounds weird cranking over. Any ideas?
Here's a video of me trying to start the car:
And here's what the old timing belt looked like.
The section cut out is where the crankshaft pulley goes. It almost seems like the camshafts completely stopped and the crank kept spinning and stripped all the teeth around it out. But the engine seems to turn over fine. We were thinking it could have dropped a valve, but you cant really see the valves with only the valve cover off. I didn't have the tool to test the compression, but I'm going to go buy an adapter tomorrow for it.
Do you guys have any idea of what it may be?
So yesterday I was cruising along in 5th gear around 3k rpms and my car just died in the middle of the road. I heard a pop, and some clicking, then I pulled over in a parking lot with the momentum I had. When I would crank the car again, it sounded weird, as if it the starter was freely spinning the motor with no resistance. I popped the oil cap off and the camshaft wasn't moving. Turns out the timing belt stripped all the teeth around the crankshaft gear. I replaced it today, put it all back together and it won't start. It is making the same starting noise it was making before. Normally the car has a distinctive starting sound that most Miatas have, it's hard to describe the sound other than its smoother, almost freely spinning. I checked to see if it had fuel and spark, and it had both. The AFR went richer after cranking the car a few times and the spark plugs were sparking. I believe the timing is pretty spot on, but even if it was off a tooth or two, it should still do something, right? At this point I don't know what to do. Tomorrow I'm going to run a compression test on the motor, but I don't really think that's gonna tell me much. Any help would be greatly appreciated.
Next day:
I checked the crank position plate and it is convex out as it should be, and I also replaced the crankshaft position sensor with a brand new one. Checked the timing again, and had a second opinion, looks perfect. Still won't start. Still sounds weird cranking over. Any ideas?
Here's a video of me trying to start the car:
And here's what the old timing belt looked like.
The section cut out is where the crankshaft pulley goes. It almost seems like the camshafts completely stopped and the crank kept spinning and stripped all the teeth around it out. But the engine seems to turn over fine. We were thinking it could have dropped a valve, but you cant really see the valves with only the valve cover off. I didn't have the tool to test the compression, but I'm going to go buy an adapter tomorrow for it.
Do you guys have any idea of what it may be?
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06-10-2017, 10:45 AM
#6
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Join Date: Mar 2017
Location: Granbury Texas
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Sounds like you bent valves. Most BPs are non-interference but larger cams, shaved head, oversize valves can lead to bent valves.
Put crank at TDC 1/4 (normal timing mark) then either do a leak down on both cylinders 1-4 (one will be at TDC compression stroke the other will be TDC exhaust) or below (poor mans leak down).
Don't have a LD tester, no prob. Just take the check valve out of a compression tester hose (2 piece style with separate hose that screws into head) and apply compressed air directly to the tester hose.
One cylinder should hold air the other should not (you can hear difference). If you have flow on both cylinders you have bent valves...
Rotate engine 360 degrees, now the one that held air shouldn't and the one that was flowing should. Anyone with air and a compression tester should be able to do a half-assed LD test. It will not give you percentages but it will tell you if you have bent valves.
Another check is valve clearance check. Have butt-loads of clearance, bent valves...
Test with air- fail, pull VC and check clearance, fail- pull head to inspect...
Hope this helps
Rick
Put crank at TDC 1/4 (normal timing mark) then either do a leak down on both cylinders 1-4 (one will be at TDC compression stroke the other will be TDC exhaust) or below (poor mans leak down).
Don't have a LD tester, no prob. Just take the check valve out of a compression tester hose (2 piece style with separate hose that screws into head) and apply compressed air directly to the tester hose.
One cylinder should hold air the other should not (you can hear difference). If you have flow on both cylinders you have bent valves...
Rotate engine 360 degrees, now the one that held air shouldn't and the one that was flowing should. Anyone with air and a compression tester should be able to do a half-assed LD test. It will not give you percentages but it will tell you if you have bent valves.
Another check is valve clearance check. Have butt-loads of clearance, bent valves...
Test with air- fail, pull VC and check clearance, fail- pull head to inspect...
Hope this helps
Rick
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06-10-2017, 11:21 AM
#7
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^ That, or, you know, just a regular ole' compression test. (After having fully charged the battery. And always run compression tests with all plugs removed.)
Do you have any pictures showing the orientation of the crank and cam gears from after the new belt was installed but before the covers went on? I agree that from the the video posted, it's not making the normal chugging sound you'd hear from the started working against the compression cycles of the engine. Cams being significantly out of time will cause this.
Do you have any pictures showing the orientation of the crank and cam gears from after the new belt was installed but before the covers went on? I agree that from the the video posted, it's not making the normal chugging sound you'd hear from the started working against the compression cycles of the engine. Cams being significantly out of time will cause this.
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06-11-2017, 02:17 AM
#9
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Location: Santa Clara, CA
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How closely did you inspect the cams?
Stripping all the teeth off right at the crank pulley is unusual and makes me wonder if there's a seized cam or something. Perhaps when you turned the starter it just stripped all the teeth off the new belt as well.
--Ian
Stripping all the teeth off right at the crank pulley is unusual and makes me wonder if there's a seized cam or something. Perhaps when you turned the starter it just stripped all the teeth off the new belt as well.
--Ian
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06-11-2017, 10:27 PM
#11
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Location: Winston Salem, NC
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Anyways, I got the car running again. I replaced the camshaft position sensor as well, and it still didn't seem like it was gonna start. After like 5 or 6 tries it finally started. I'm still not sure what exactly it was, but I believe it is back to normal. Thanks everyone for all the help, you guys are amazing.
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