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Discussion Starter · #1 ·
On my 2003 4 cylinder optima, it wouldn't start. Would crank but not turn over. One month before, the same thing happened so my mechanic replaced the fuel pump and strainer, cleaned my tank and all was good except for hesitating and rough Idling. Replaced the coils and injectors and was all good. This time we replaced the entire fuel pump assembly because some of the clips and wires were close to breaking. No start at all. Will start with starter fluid and then stall . Code showed low volume mass air flow sensor. Replaced maf. No difference. Any ideas? My mechanic is pulling his hair out. Thought there was a 2nd fuel filter, but after following the lines from the pump to the firewall, found nothing. Help!
 

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2011 Kia Optima
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Check fuel pressure at rail, then you'll be able to discount the fuel system if pressure is correct.
 

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2018 Optima EX, 2019 Stinger GT2 AWD
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Since it starts with starter fluid, you have spark. Since it stalls shortly after, then you have no fuel going into the cylinders. Turbonut is correct, check fuel pressure to make sure you have pressure at the injector rail to determine if there is a fuel pump problem or a computer problem.
 

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Discussion Starter · #4 ·
We capped off the fuel return and the car runs great. Checked pressure on return line and was 90.Replaced fuel pressure regulator and it still stalls .
 

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What's the fuel pressure without the return line blocked off?
You can also check it with the key on engine off, but it will be
slightly lower.
 
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