1991 NA 1.6L won't start - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-06-2012, 07:15 PM   #1
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Default 1991 NA 1.6L won't start

I just bought a 1991 mariner blue Miata two weeks ago, and I have been having a lot of fun fixing it up. It ran fine when I got it, but it had been sitting for somewhere between 3-6 years in a garage without being run at all. The ODO says 138k miles, but I have receipts that prove that a new engine was put in about 12k miles ago, so the engine SHOULD be almost new (though that was back in 2002 or so before it was garaged).

I replaced all of the fluids (brake fluid, clutch fluid, transmission oil, diff oil, engine oil/filter) the air filter, fixed the trunk and glovebox locks, replaced one tail light, took out a bunch of defunct aftermarket stereo and alarm system stuff, and it was still running great. After that, I replaced the stock cat/catback (which had some damage and was warped/rattling) with a JR High-flow cat and a less damaged stock catback that I bought on Craigslist. Both looked fine, doubt they could be related (I did read at least one post where a clogged cat-converter caused problems, but i don't THINK it's related).

Anyway, the problem at hand: I was driving it a very short distance to a friend's place to show it off, and I went over a fairly rough bump in the road (this MAY or may not be coincidental) and a few seconds later the engine was losing power until I just rolled to a stop. I turned it off thinking I had stalled but I heard it actually turn off, and then after that it wouldn't start. It alternates between just cranking away and whining with no vibration, and then vibrating the engine a lot like it's trying to catch but just NOT. I have observed exhaust gas coming out of the *intake* during this stage. This does not seem like a good thing to me!!!

I checked the diagnostic codes and it is throwing code 3 (No G Signal) which supposedly signals issues with the CAS. I checked the fuel pump by shorting GND and F/P, and I can hear it whining along. I verified that the camshaft does spin by taking off the oil cap and watching while a friend tried the ignition.

I did some testing of the CAS wiring as per these pages:

Our Friend CAS
Untitled Document

I am getting 12v and +5/+5 with the key turned to ON, and the ground wire appears to give a good ground... I am not sure how I am supposed to test the voltages with it plugged in (and attempting to start the engine), since when I plug it in there is no way to get the voltmeter sensors to touch the wires. How do people normally test this? Anyway, I got a used CAS (supposedly working, though leaking a bit of oil) from a local contact, and swapped it out, with no effect. Still won't start, same exact symptoms.

The other advice I've been given is to check to see if the timing belt slipped, as possibly the rather large bump I hit could maybe have funked with the tensioner and caused it to slip a few teeth? I took the valve cover off to see if I could check the camshaft positions, but I ran out of time trying to figure out how to get piston 1 to TDC. I am going to give that another go tonight, but in the meantime, here is a pic of the engine with the valve cover off:
http://i.imgur.com/uQplx.jpg

Is there any other advice you guys can give me? I did buy this as a project car, but I wasn't planning on having to do in-depth engine/electrical work quite yet (I was really hoping the engine would hold up until I worked my way up to a 1.8L swap)...

TLDR: engine won't start, code 3 "no g signal", sometimes seems to send exhaust out of the INTAKE while cranking :(
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Old 08-07-2012, 12:59 AM   #2
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It looks like you need to turn the bottom pully (crankshaft) clockwise approx 180 degrees.

The #1 cylinder intake cam lobes need to be pointing about 9 o'clock and the exhaust cam lobe for #1 needs to be pointing at 3 o'clock.

You need to remove the #1 spark plug and carefully put a dowl or something in there to see when the piston has reached TDC. Once you find this look at the ignition timing mark on the balancer and see if its close to 0 degrees. The piston will reach top twice though and you need to make sure your at the compression stroke. This is when you make sure the cam lobes are where I mentioned above.

Once you have done all of this look and see if the cam gears are timed properly.

The Intake cam should have "INT" mark lined up with the arrow (12 o'clock) and the "Exh" mark pointing at about 4 o'clock.

The Exhaust cam should have "EXH" mark lined up with the arrow (12 o'clock) and the "INT" mark pointing at about 8 o'clock.

If all of this lines up you need to look elsewear for your problem.
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Old 08-07-2012, 11:35 AM   #3
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Ok so I took a video and showed it to a friend, and he says my crankshaft bolt is MISSING?!?! WTF

See 24-26 seconds in this video:
https://www.youtube.com/watch?v=Y0WxiyEvYSI&t=0m24s

I guess that pretty well explains why I was having trouble figuring out how to get piston #1 to TDC...

Last edited by rm_you; 08-07-2012 at 12:54 PM.
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Old 08-07-2012, 01:04 PM   #4
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Old 08-07-2012, 04:39 PM   #5
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Quote:
Originally Posted by krissetsfire View Post
Yeah, I need to figure out which version of the bolt I have... Unfortunately, the engine was replaced in 2002 (before I owned the car) and I have no idea which version they put back in, so I can't use the VIN method. I had assumed they would use a version with the properly sized bolt that would not suffer from the previous issues. I guess it's still possible they did, and this is something unrelated, but I am going to verify tonight.
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Old 08-07-2012, 06:06 PM   #6
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You can use the VIN method. The motors have VINs too. The oil pan and or the block will have one on there. Be sure to read up on the woodruf key threads. Do a timming belt and water pump while your in there. Its cheep and well worth the effort to know you can move on to more fruitful projects.
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Old 08-08-2012, 12:54 AM   #7
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So, here's another video of the crankshaft pulley (where the bolt should be). It looks like it actually sheared off in there... So I guess it probably doesn't matter what the VIN is, as it's not going to just be a replacement bolt. I'm going to need to take the engine out and see if I can get the rest of the bolt drilled out or something, and if not, I guess I switch to a new 1.8L engine. :/

1991 Miata Crankshaft Bolt (Sheared?) :( - YouTube
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Old 12-15-2013, 07:25 PM   #8
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Post no spark

i was driving my car i hit a bumb it shut off and turned on right away after that... drove fine on the way back after that. i parked it for the night... work up in the morning and my started was clicking like the battery was low. i jumped my car and it cranked but didnt start. i took out the spark plug checked if i had spark and found out im not gettin any spark.. any ideas?? i checked main fuse relay i changed spark plugs, and coil pack as of now. still no spark :/
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Old 12-15-2013, 07:48 PM   #9
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You should make a new thread instead of resurrecting this old one.
But make sure your plug is grounded when youre testing spark, I had a friend who was convinced he didn't have spark at his plugs, but in reality forget they needed to be grounded for the spark to fire.
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