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Discussion Starter #1
I have been reading all kinds of forums and cant find one similar to what I'm trying to figure out.

My 1990 Supra Turbo cranks but wont start (occasionally), most times it fires right up. When this happens I turn the key off then on and it fires right up, other days I have to wait 5 minutes and try again and it usually goes. When it does fire, it starts up and runs great (had a idle issue a few months ago).

The strange thing I've noticed is when it refuses to start, it doesn't show any RPM on the gauge. So I'm starting to think its a cam position sensor?

Any help or idea's would be great. As I said, I read a bunch of forums and have done a ton of tests already. No parts have been changed for this yet.



Thanks.
 

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check your sensors and reset your alarm as you said it takes 5 minutes to start ive heard something about the alarm system glitching and not allowing the engine to start right...
 

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It has nothing to do with the alarm system. When the alarm system is improperly working the engine will not crank at all, the lights inside will all just fade at the moment you try to start as if you lose power completely. Then you have to get out of the car, close our door, re-lock and unlock the car and then it should work. His problem is different. His problem is after cranking over. The basics of an engine are air, fuel, and ignition. Without one of those 3 your engine will not start. So it's either there is no fuel being delivered at times aka bad connection to pump, there is a massive intake leak which from your description I doubt, or connection to the ignitor is bad. Check your spark plugs and wires and all the wires connected to the ignitor because all those wires are most likely brittle and old. Could also be improper timing too so give that a check and make sure your cam gears are correctly aligned to TDC. Good luck
 

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No rpm on the gauge means no spark, so yes the CPS is a good place to start. The wiring being brittle/frayed near the connector is a common issue.
 

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If you've never touched the cam position sensor and the connection to that is fine then I highly doubt that needs adjustment. After rebuilding the head I inserted the cam position sensor a completely wrong way and the engine still started but it ran like absolute garbage. So I don't think that's your problem but it doesn't hurt to check
 

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Discussion Starter #6
Thank you everyone, I'll check out the connectors and wiring tomorrow hopefully I find something there.

Would a bad CPS cause it to idle low/rough? Back when I had my idle issue I changed a few parts and then one day it just started idling properly again.
 

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Thank you everyone, I'll check out the connectors and wiring tomorrow hopefully I find something there.

Would a bad CPS cause it to idle low/rough? Back when I had my idle issue I changed a few parts and then one day it just started idling properly again.
yea check your ignition timing hehe
 

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The issue is just brittle and frail CPS wiring. The CPS is fine if, when the car starts and runs, there are no issues. If the tach is not moving, then the CPS is not sending a signal and therefore will not start.

Next time it is not starting, have someone wiggle the CPS harness and push the plugs together a little tighter. I would be almost anything it will start right up after that. This is a very common thing with these cars as they age and with that harness being on the exhaust side of the engine bay.
 
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