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Old 08-01-2009, 03:25 PM   #1
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Default See if you can solve this one

The car is a 90 Mazda Miata with a JacksonRacing supercharger and I was going down the highway about 75-80 mph running about 3800 rpms. All of a sudden.........my rpms dropped to zero and stayed at zero and I couldn't get any power at all. Pushing my gas pedal did nothing. The kicker is that when the rmps dropped my engine was still running and I was able to turn on the blinker to get in the safety lane. No lights came on the dash. So I cut the engine and opened the hood to check the hoses and belts and everything was fine! So what would cause your RMPs to drop and not let your gas pedal work but not effect anything eletrical (because radio was working and warnig flashers were working) and still let the engine run? Since I turned it off my engine turns but won't start. I am puzzled...I need help on this one and I can't afford a mechanic

Jordan
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Old 08-01-2009, 03:30 PM   #2
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Jordan, you are screwed.

Post more info about your setup if you want any help form anyone on here.
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Old 08-01-2009, 03:59 PM   #3
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If the RPMs dropped to zero but the engine was still running then your RPMs didn't really drop to zero. So I'd start by looking at electrical connections, especially anything that had been modified because of the supercharger. What's being used to control your timing?? Check the connections at it and even bypass it to see if it has gone bad. Just remember don't make too much boost if it starts and runs without the timing controller. I have seen things like a J&S box fail or the connector coming out of a Bipes unit. "Fixed" a car at the Gap last weekend after the guy had done a ton of stuff to a car that wasn't running by asking what his timing controller was and finding the connector unplugged.
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Old 08-01-2009, 04:03 PM   #4
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Does the engine crank? If yes then check if you are getting spark. If no spark then check your ignitor.
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Old 08-01-2009, 04:21 PM   #5
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The engine cranking doesn't indicate it has spark, all it indicates is the engine isn't seized and the starter motor is working.
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Old 08-01-2009, 04:22 PM   #6
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CAS failure?
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Old 08-01-2009, 04:27 PM   #7
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your blinker, radio, and most other electronics work when your key is in the second position. the engine wasnt turning as you were pulling off to the side. ignitor or something ignition related sounds right.
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Old 08-01-2009, 05:54 PM   #8
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Timing belt. With trans in gear the engine will still "run" but the cams won't turn, won't turn the CAS, won't run, and won't indicate RPM.

What you describe is the exact thing that happened to my friends 90.
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Old 08-01-2009, 06:12 PM   #9
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+1, open the oil cap and see if the cams are turning when you crank it. Classic timing belt failure.
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Old 08-01-2009, 06:16 PM   #10
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Quote:
Originally Posted by elesjuan View Post
Timing belt. With trans in gear the engine will still "run" but the cams won't turn, won't turn the CAS, won't run, and won't indicate RPM.

What you describe is the exact thing that happened to my friends 90.
Sounds like a winner to me. Thank god for Non interference motors.

To check for this pull the valve cover and put a wrench on the crank. If the cams don't turn with the crank your belt is gone. Also note that it's possible that a few teeth are missing from the belt (quite a few if it won't run at all). Be sure to look at the teeth as they pass between the cam gears.

Good luck, if it's a belt the cost to fix is 25$ for a new belt and 20 for a haynes manual (if you don't already have one). May as well do a water pump while your in there.
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Old 08-01-2009, 06:19 PM   #11
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Uh noob, if you pull the valve cover, I think it would be easier to LOOK AT THE GOD DAMNED TIMING BELT than cranking the engine by hand. Just a thought.
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Old 08-01-2009, 06:19 PM   #12
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Originally Posted by AlexandertheOk View Post
To check for this pull the valve cover and put a wrench on the crank. If the cams don't turn with the crank your belt is gone.

Or he could, you know, look at the lack of a timing belt. That's a reasonably good indicator.

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Old 08-01-2009, 06:26 PM   #13
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You guys!
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Old 08-01-2009, 06:28 PM   #14
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Quote:
Originally Posted by Savington View Post
Or he could, you know, look at the lack of a timing belt. That's a reasonably good indicator.


I was unaware timing belts vaporized when broken. I would hope that if it was totally missing he wouldn't proceed to turning the crank. I thought maybe it could be missing a few teeth but I've never broken a timing belt.
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Old 08-01-2009, 06:30 PM   #15
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Don't you get a ******* attitude in here! Check it at the door fella!
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Old 08-01-2009, 07:08 PM   #16
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I believe what we're attempting to say through a massive amount of sarcasm, is that in order for teeth to be stripped off the belt, and have the engine not crank, there would have to magically be missing teeth from the area around each cam sprocket, as well as around the entire crank sprocket. Theoretically possible, however you'd obviously see missing teeth around the cam sprockets once you remove the valve cover, again making turning the crank by hand unnecessary.
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Old 08-01-2009, 07:35 PM   #17
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Quote:
Originally Posted by AlexandertheOk View Post
I was unaware timing belts vaporized when broken. I would hope that if it was totally missing he wouldn't proceed to turning the crank. I thought maybe it could be missing a few teeth but I've never broken a timing belt.
Because missing a few teeth will sure make the motor completely shut off at 4000rpm with no warning. Yes sir-ee.




Instant shutoff, no blown fuses, cranks fine = timing belt failure. If you don't understand how to diagnose a timing belt failure with the valve cover off, you shouldn't be allowed to open your hood.
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Old 08-01-2009, 07:42 PM   #18
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Your right, I fucked up.

Good luck to the OP
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Old 08-02-2009, 05:42 AM   #19
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Huh, the timing belt DOES sound like a good candidate, but... so does the fuel injection fuse? Certainly a simple one as well, slightly less likely but an easy fix. :-) It'll shut off really quick that way, and yes, no tach.

Wait, aren't the tachs mechanical in a 90? Something is, my friend's 90 is SO f'ing noisy from a bad tach cable or speedo.
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Old 08-02-2009, 07:26 AM   #20
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Speedo is cable driven in an NA
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