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Old 05-25-2013   #1
sdickens
 
Join Date: Apr 2012
Location: Oviedo, FL
Posts: 12
Default 1990 ZR-1 cranks but won't start

Car is my daily driver. A couple months ago I was Leaving work one day tried to start it, would crank but not start. I had it towed to my*mechanic, they tried to start it, but same issue.
They pushed it into their bay, set it up for diagnostics and then it started right up and every time after that.

Yesterday the issue came back. was out to lunch and when done the car would crank but not start. I got a ride back to the office and end of the day back to my car. It started right up.

Any ideas on what would cause this?

Thanks,

Sam
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Old 05-25-2013   #2
tpr60
 
Join Date: Feb 2011
Location: Salinas, Ca
Posts: 159
Default Re: 1990 ZR-1 cranks but won't start

I had a s10 blazer that would do the same thing. Ended up being the fuel pump, it was border line on fuel pressure. Would start with 40 psi or above but at 39 psi or below it was a no start.
Good luck.
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Old 05-25-2013   #3
scottfab
 
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Location: Portland Oregon metro area (Washington side)
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Default Re: 1990 ZR-1 cranks but won't start

Likely primary fuel but strange because even if the engine is warm the secondary pump should allow for a start then quickly you should stall because it shuts down (by design) and the primary is left to supply fuel. The fact that it starts ok when cold also points to primary fuel pump because when cold both pumps run.

You need to attach a fuel pressure gauge then warm it up and watch.
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Old 05-26-2013   #4
sdickens
 
Join Date: Apr 2012
Location: Oviedo, FL
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Default Re: 1990 ZR-1 cranks but won't start

I don't think it has to do with being cold. The first time it has the issue was after sitting in the parking lot at work the entire day.

I left it there over night, went back the next day and it still would not start. That's when I had it towed, didn't start for the mechanic until after pushing it into his bay.
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Old 05-29-2013   #5
CosbySweater
 
Join Date: May 2013
Location: Nor Cal
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Default Re: 1990 ZR-1 cranks but won't start

Could be a temperamental ckp, as stated above though I would check fuel pressure first, had the same problem with a car I was messing with, it would run perfect, then all of a sudden try to start it again and no start, hooked up my laptop and noticed no rpm signal on cranking, replaces the sensor and it's been good ever since
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Old 05-29-2013   #6
Schrade
 
Join Date: Dec 2012
Location: NC
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Default Re: 1990 ZR-1 cranks but won't start

Quote:
Originally Posted by CosbySweater View Post
Could be a temperamental ckp, as stated above though I would check fuel pressure first, had the same problem with a car I was messing with, it would run perfect, then all of a sudden try to start it again and no start, hooked up my laptop and noticed no rpm signal on cranking, replaces the sensor and it's been good ever since
Welcome onto the boards there...
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Old 05-29-2013   #7
CosbySweater
 
Join Date: May 2013
Location: Nor Cal
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Default Re: 1990 ZR-1 cranks but won't start

Also, bring a spark plug with you if your daily driving the car still, when it happens pull one wire and check if it's got spark, if it does that immediately cancels out the ckp in theory because that is what is the trigger for the ignition system on these engines iirc
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Old 05-29-2013   #8
Hog
 
Join Date: Jul 2010
Location: Woodstock, Ontario, Canada
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Default Re: 1990 ZR-1 cranks but won't start

Quote:
Originally Posted by CosbySweater View Post
Also, bring a spark plug with you if your daily driving the car still, when it happens pull one wire and check if it's got spark, if it does that immediately cancels out the ckp in theory because that is what is the trigger for the ignition system on these engines iirc
Yes, no ckp signal = no spark. Good idea, its a quick indicator for having spark or not, plus you dont have to pull a plug out of teh head.

Welcome!

peace
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Old 06-25-2013   #9
sdickens
 
Join Date: Apr 2012
Location: Oviedo, FL
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Default Re: 1990 ZR-1 cranks but won't start

I had the issue again over the weekend. I had a code reader with me this time and it was code 21 Throttle Position Sensor high. Does this sound like something that would cause this issue? Makes sense if it thinks the car is at full Throttle not to start?

Thanks,

Sam
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Old 06-25-2013   #10
scottfab
 
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Default Re: 1990 ZR-1 cranks but won't start

The FSM makes no mention of a "no start" if TPS is stuck high.
Dunno......
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