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hard start problem

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Old Oct 7, 2013 | 03:02 PM
  #1  
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
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hard start problem

Well ive being having this problem for while of having hard start up on my car. I have already replaced the fuel pump, and injectors and im still having the exact same problem. I have a 91 305tpi, once the car starts up it runs fine its just takes a while to start around 10 seconds of cranking. Any pointers on what i could check id appreciate it.
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Old Oct 7, 2013 | 05:04 PM
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From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: hard start problem

Originally Posted by SiCkRs
just takes a while to start around 10 seconds of cranking. .
Very common problem
Highly likely the pump relay is not working to prime the rails key on as it should so you are waiting for the backup OP pump
switch to run the pump and build pressure while cranking over

Check the relay works for 2 sec key on , and that the system primes and holds correct fuel pressure there after
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Old Oct 7, 2013 | 05:16 PM
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
Axle/Gears: 3.42
Re: hard start problem

It does prime for the first two seconds when i turn the key on position. I dont have a gauge to check it right now but last time i did that i would get 45psi and drop slowly to about 35psi
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Old Oct 7, 2013 | 08:15 PM
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From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: hard start problem

Originally Posted by SiCkRs
last time i did that i would get 45psi and drop slowly to about 35psi
Maybe time to do the prime and hold test again ?
Quick test would be to hot wire the pump to run full time ( so you have continuous rail pressure before cranking ) and see if it starts faster.
If not , it is not a fuel problem

Putting 12V to terminal G of the ALDL connector runs the pump


]
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Old Oct 7, 2013 | 10:18 PM
  #5  
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
Axle/Gears: 3.42
Re: hard start problem

Ok so if i get my power probe and put 12v to the pin G the pump should run non stop?
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Old Oct 7, 2013 | 10:36 PM
  #6  
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From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: hard start problem

Originally Posted by SiCkRs
Ok so if i get my power probe and put 12v to the pin G the pump should run non stop?
Correct.
The only proviso being terminal G goes through the closed contacts
( red wire into relay . diagram below ) of the pump relay so they have to functional

If the G terminal fails you can always jumper the pump connectors (org to tan /wht) on the relay connector to achieve the same result


]
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Old Oct 9, 2013 | 03:58 PM
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
Axle/Gears: 3.42
Re: hard start problem

Oh ok i will try that asap once it stops raining.
Thanks.
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Old Oct 10, 2013 | 06:45 PM
  #8  
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
Axle/Gears: 3.42
Re: hard start problem

ok well today i noticed when i turned the key into on position it did not turn on the pump and had the long cranking after that. Still havent tested it with putting 12v to the g terminal though.
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Old Oct 10, 2013 | 07:15 PM
  #9  
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
Axle/Gears: 3.42
Re: hard start problem

OK well i just tried doing what you said putting 12v for the fuel pump and i had the same exact problem. But once i started the car i turned it off right away and kept cranking it and it would start right away. I might make a video since im not good at explaining the problem.
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Old Oct 10, 2013 | 08:02 PM
  #10  
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From: Not in Kansas anymore
Car: 82 Z28
Engine: 383 SP EFI/ 4150 TB
Transmission: T400
Axle/Gears: QP 9" 3.73
Re: hard start problem

Originally Posted by SiCkRs
i just tried doing what you said putting 12v for the fuel pump and i had the same exact problem.
Was the pump running full time?

What was the fuel pressure at the engine?
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Old Oct 10, 2013 | 09:38 PM
  #11  
SiCkRs's Avatar
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From: Norwalk, CA
Car: 91Z28
Engine: 5.7 ls1
Transmission: 4l60e
Axle/Gears: 3.42
Re: hard start problem

yes it was running full time.
pressure was at 44psi while cranking
I was thinking could my timing make it take long time to start?. Or something with my ignition because once it starts, i have to rev it up to about 2500-3000 rpm or else it will die right away.
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